Service Bulletin | Due to recent improvements in both the Liquid Roof and Liquid Rubber we have improved the cure time greatly. By doing this we have noticed a shorter pot life after the catalyst is incorporated into the base material. Once the catalyst is added the reaction period begins. The working time to apply Liquid Rubber and Liquid Roof is between two hours and four hours depending on the temperature. The higher the temperature the shorter the working time. Once the catalyst is mixed into the EPDM it must be used. Pro Guard does not warrant catalyzed product that is not used within the proper time frame.

Liquid Rubber EPDM ®

F9981 White | F9999 Black | F9988 Gray | F9961 Low Voc

Liquid Rubber has been on the market for nearly three decades and during that time many different applications have been tried and tested.  An extensive amount of information has been compiled and is available here.

Any information that pertains to Liquid Rubber also pertains to Low VOC Liquid Rubber except the VOC content. Liquid Rubber® provides a seamless, single coat, roof coating that can be applied up to 6 times thicker than your standard elastomeric. Liquid rubber® is ideal for recoating EPDM roof membranes, troweled concrete, weathered metal roofing, foam, weathered siding and more. Liquid Rubber® will withstand ponding water or immersion indefinitely and Liquid Rubber can be installed over lightly rusted surfaces without a primer. Uncured Liquid Rubber® will not be damaged by freezing temperatures.

Learn more by watching the video below:

Pro Guard Coatings is now accepting applications for qualified distributors in Canada. Contact us below for information.

Contact Us Today




pro_guard_product_tilesLiquidRubber-05 (1)


PG EU SDS 9981

Liquid EPDM Rubber®

F9981 White
F9999 Black
F9988 Gray
F9961 Low Voc

Product Data Sheet

Liquid Rubber ® will cover up to 46 square feet per gallon on a very smooth surface.  Normal coverage is 40-42 square feet per gallon on an average substrate. The required 20-mil film thickness will be achieved when the above spreading rate is used.

Cure Conditions:
The cure rate of Liquid Rubber® is temperature dependent; i.e. higher temperatures will accelerate the cure and lower temperatures will retard it. Contact with air is another requirement. If, for example, a rain shower develops before material has cured [material may still be wet] and water collects on the surface the following condition will prevail. Material that is still wet will prevent water from penetrating the film; however, the curing process will not begin unless material is exposed to air. The material under water will remain uncured until the water has evaporated and the surface again becomes exposed to air, at which time the curing process will begin.

Surface Preparation
Roof surface should be dry and free of dirt and loose gravel at time of application.

Mixing Directions
Proper incorporation and thorough mixing of the catalyst is critical to achieving desired cured film properties and should, therefore, be done with great care. Container is filled low to allow room for mixing as well as the addition of the catalyst. Insert mixing paddle in Liquid Rubber® and mix for approximately one minute so that material is moving uniformly and has formed a vortex. Slowly add catalyst into this vortex at a rate, which allows it to be incorporated without puddling. DO NOT pour catalyst on top of Liquid Rubber® prior to starting mixer. After all the catalyst has been added, the mixer (if hand held) should be moved in a circular fashion around the periphery of the pail as well as up and down to insure that the catalyst is completely and uniformly mixed. Periodically scrape the sides with a rubber or metal spatula to incorporate the stagnant layer of material adhering to walls of pail.

The information presented herein is furnished free of charge and is based on technical data that Pro Guard believes to be reliable. It is intended for use by persons having technical skill and is at their own discretion and risk. Since conditions of use are outside our control we make no warranties, express or implied, and assume no liability in connection with any use of this information. Nothing herein is to be taken as a license to operate or a recommendation to infringe any patents.

Acceptable Substrates
EPDM Coatings

“Liquid Rubber is designed to recoat structurally sound existing roof and protective materials.  They should not be used in place of roofing membranes”.

The following are recommended substrates to coat:

Metal – Coated or Galvanized Steel
Weathered Aluminum
Weathered Copper
EPDM Rubber membrane
Concrete (except foot traffic surfaces)
Urethane Foam
Primed Wood
PVC Sheet and Pipe
Acrylic Sheet
Sponge Rubber insulation

Do Not use Liquid Rubber on the following substrates:

Built up asphalt roofs
Asphalt shingles
Modified asphalt roll roofing
Stainless steel
Silicone caulk
Foot traffic surfaces
Hypalon Membrane
TPO- We do not yet ”recommend” this application. If you choose to use Pro Guard Coatings products, as many customers have, Proflex Primer top coated with Liquid Rubber has been reported to us as a successful combination for TPO. 

ProFlex Primer F1519/2 and Liquid Rubber
for Modified Asphalt Roll Roofing


Torch Down and APP roll roofing are modified asphalt products that experience chalking and then crack as a result of UV degradation.  If these products are coated before they reach the cracking stage their life expectancy can be considerably extended.  Coating selection and climate zone, however, are very important considerations.  Solvent containing coatings should not come in direct contact with asphalt products unless they also contain asphalt.  Since asphalt products are thermoplastic, top coating them with incompatible products can lead to early failure in areas that experience winter temperatures down to 0° F

A coating system that can be used in climate zones that do not experience below 0° F temperatures consists of the following:

Primer: 1519 Pro Flex Primer for asphalt, spread at 90 sq. ft./gallon.

Topcoat: Liquid EPDM Rubber; 9981 White, 9988 Gray, 9999 Black

spread at 45 sq. ft./gallon.

This combination will produce an average 37 mil dry film thickness.

Modified Asphalt Roll Roofing was developed as an alternative to the use of hot melt tars.  Although it was an improvement over the hot melt it still suffers from the accelerated weathering characteristic of asphalt products.  Patching and recoating of asphalt roofs has primarily been done with cold applied asphalt based coatings.  Their thermoplastic nature and low UV resistance, however, produce only short term fixes while adding weight and making future repairs more difficult.

The F1519/2 ProFlex Primer for Asphalt Roofs makes it possible to apply Pro Guard Coatings’ Liquid EPDM Rubber product in place of the cold applied asphalt coatings.  This will result in a white, heat reflective and much more durable surface.

The F1519/2 Proflex Primer for Asphalt Roofs is a flexible epoxy filled with finely ground rubber.  It will bond to and stabilize the weathered surface and create a barrier to any solvent penetration when the Liquid EPDM Rubber Coating is applied.


Cut and remove any loose material.  Low spots may be filled by using multiple layers of Butyl Tape or the F1519 Proflex Primer itself.  The 1519 can also be used as an adhesive to re-adhere loose membrane.

Mix Parts A & B according to label directions and pour the mixture on roof surface; distribute the material with a rubber edged squeegee and follow up with an adhesive roller to make sure that the entire surface is coated.  Be aware that the pot life of the mixed Proflex Primer can be less than 1 hour depending on temperature.

Use a polyester fabric to lay into the wet Proflex to reinforce all cuts and areas that are cracked and weak.

Allow the 1519 Primer to cure overnight and apply the Liquid EPDM Rubber topcoat while the primer is still tacky on the surface.

NOTE: The above procedure is not recommended for use in climate zones that experience temperatures below zero degrees F.

The above data is gathered in a controlled Laboratory environment. Your conditions will vary. Pot Life, Gel Time, Dry Time and Cure Time will all be affected by ambient as well as surface temperatures. Higher temperatures shorten the time you have to work with the product. Always mix thoroughly and immediately pour out of the container onto the surface to be coated. Only mix the amount you can easily spread within 30 minutes.

EPDM Liquid Rubber®

Application Guidelines

This product is a high solids solution of EPDM Rubber. It converts from liquid to solid elastomer via a unique free radical cure mechanism which works at temperatures of 55° F and higher.  The characteristic high viscosity and tackiness of Liquid Rubber requires modified application methods from those of conventional coatings.  It is the shape of the surface (flat, curved, corrugated, standing seam, etc.)  that will determine the methods of application to be used.

EPDM Liquid Rubber® can be applied directly on many types of substrates that have solid, stable, non-porous and uniform surfaces such as flat roofs. For most substrates, primers are not necessary. As an example, some types of substrates that can be coated with EPDM Liquid Rubber®  without a primer are:

  •  EPDM Rubber Membrane on flat or sloped Roofs
  •  Weathered Steel Siding
  •  Weathered Fiberglass
  •  Weathered standing seam and corrugated metal roofs
  •  Weathered Vinyl, PVC and Polycarbonate plastic
  •  Foam insulation for pipe
  •  Cast Concrete foundations

There are two basic Methods of Application,  match your roof type to one of the methods below for the most likely application procedure.

Airless Spray
Standing Seam
Irregular Surfaces
5,000 sq. ft. & above

Squeegee and Roller
Flat Roofs
5,000 sq ft & below

Applying over Non Porous Surfaces:

Applying over EPDM Rubber Sheets

Our EPDM Liquid Rubber® can be directly applied over EPDM Rubber Sheets with little preparation other than cleaning. It is recommended, however, that for larger and older projects you use our Surface Conditioner F9910 prior to application of our EPDM Liquid Rubber®. Surface Conditioner F9910 was formulated to promote better adhesion on EPDM Rubber Sheets when a thorough cleaning is not practical.

On some materials, such as EPDM rubber sheets, some swelling may occur due to solvent absorptions after applying EPDM Liquid Rubber®. This is normal. This swelling will recover with time and heat. In 80° F or so, allow 7 to 14 days to recover. In colder temperatures, recovering will take several weeks, as much as 6 to 8 weeks in 60° F.

EPDM Liquid Rubber®

Applications for Wood
Cast Concrete

Lumber and Plywood

Liquid Rubber adheres well to all types of wood.  If the rubber is applied directly to the wood, however, its appearance will not be uniform because of the differing porosities of the surface.  This condition can be avoided by first priming the wood with an oil based primer or Pro Guard’s Proflex Primer®.  Some applications where Liquid Rubber works well on wood are:  Railings, Fence Posts, Planters, and Window Boxes.

Plywood Roof Decking

Liquid Rubber may be used on plywood roof decking as a moisture barrier to protect the wood but should not be used as the primary waterproofing for the roof.  The many joints and potential for warping make this an impractical use of the product.  Shingles, Metal or Roofing Membranes are appropriate roofing materials.

Coating Cast Concrete with Liquid Rubber®

Concrete that has not been trowel finished has a more porous surface which can create pinholes if Liquid Rubber is applied without a primer.  Pro Guard’s Proflex Primer® is recommended to seal the surface of the concrete but will also strengthen and reconstitute a leached or spalling surface.  The Liquid Rubber should be applied over the Proflex Primer® within 3 days.

Applying EPDM Liquid Rubber
on Wood & Plywood Roofs and Structures

In some cases Liquid Rubber can be directly applied on to dry and non-porous wood and plywood without additional preparations, however it is our recommendation that all untreated wood and plywood products be sealed with an oil-based sealer prior to applying Liquid Rubber.

Sealing the wood with a good oil based sealer will reduce porosity of the wood, minimize trapped moisture, hence reducing later rot and generally protects the wood from degradation.  When using an oil based wood sealer, follow the manufacturer’s directions and their recommended dry times.

For treated or painted wood, clean the surface with soap and water to be free of residual oils, debris and dirt.  Make sure flaking paints are removed.  Make sure the surface is dry prior to applying Liquid Rubber; work on a rain free day above 55° F, however 65°– 75° F. would be ideal.  For smooth surfaces use one gallon for every 40 sq.ft. of area you intend to coat.  Reduce this for rougher surfaces.

If you are coating larger roofs and structures, you may have several seams and joints.  If these gaps are under 1/16” gaps, you may coat over these seams without additional reinforcements or fillings.  However, if you expect excessive expansions, movement or have larger gaps, you should reinforce these seams.


  • Treat the wood with an oil based sealer and let dry prior to applying Liquid Rubber
  •  Clean and prepare the surface to be coated as directed on the label.
  •  Cut a strip of Butyl Tape to cover and bridge cracks, holes and defects.
  •  Lay the Butyl Tape flat on the surface, use a hard roller to flatten kinks out.
  •  Lay the Polyester Fabric over the butyl & defects.  The butyl tape has adhesive surfaces on both sides and will hold the Polyester Fabric in place.  Flatten the Polyester Fabric with a hard roller as necessary.
  •  Saturate & Impregnate the Polyester Fabric with Liquid Rubber.  On cure, this section will be reinforced by the Fabric-Liquid Rubber composite.

Where seams, holes and gaps are greater than 1/16”,  reinforcing, caulking or filling in with epoxy are required.

For smooth surfaces, use a spreading rate of 40 sq.ft. per gallon of Liquid Rubber.  Reduce this rate for rougher surfaces.  Work above 55 deg. F for curing to start, 65 – 75 deg. F would be optimal.  Partial cure (dry to the touch) will be achieved in 16 to 20 hrs., in 70 deg. F. temperatures.  Full cure will be achieved in 4 to 10 days in 70 deg. F temperatures.  Higher temperatures will accelerate the cure rate.


1)     Calculate Expanded Roof Surface
a)     Total  L × W  areas
b)     Establish expanded surface factor using a string or flexible tape measure.

Expanded area  =  L × W × Factor

2)     Determine Spread Rate based on Dry Film thickness desired.

Sq. Ft.      =      1600       ×       .635
Gal                dry film        volume solids
in mills         of product


How many gallons of Liquid Rubber are needed to coat a 10,000ft2 standing seam metal roof with a 20-mil average film thickness?

Expanded Surface Factor  =  1.2;  surface factor  =  .9

Expanded Area  =  10,000  ×  1.2  =  12,000ft2

Gallons needed  =  12,000ft2  ×  1600  ×  .635  ×  .9  =  262.58 gallons



Coating Cast Concrete
with Liquid Rubber®

Concrete that has not been trowel finished will have a surface that is more porous than one that has been troweled.  When Liquid Rubber® is applied directly to such a porous surface it will produce a high density of small craters in the resulting membrane.  This is caused by Liquid Rubber® actually penetrating into the pores, leaving a crater on the surface.  The following procedure is recommended to prevent the formation of surface craters.

1)   Apply a light coat of one of the following products to seal the surface:

a)   Water based Acrylic Elastomeric coating (primer or base-coat version)
b)   Solvent based Chlorinated Rubber or Hypalon product.
c)   Solvent based Neoprene Rubber product.

The choice of water or solvent-based product should be based on temperature and humidity conditions.  For water based products, relative humidity should be less than 70% and temperature 60° or higher.  Solvent-based products should be used at low temperatures and high relative humidity.

2)   Liquid Rubber® may be applied when primer application is sufficiently dry.  Water based products should be allowed to dry thoroughly, as any moisture will interfere with the adhesion of the rubber.

A single coat of Liquid Rubber® is preferable to multiple coats.

Coating Metal Roofs with Liquid EPDM Coatings

F9981 White
F9999 Black
F9988 Gray
F9961 Low VOC EPDM

Liquid Rubber may be applied on roof decks, gutters, structural steel, air conditioner enclosures, cooling towers, galvanized steel, unit heater flues, smoke stacks and chimneys, fiberglass and non porous masonry surfaces.

Surface preparation

All surfaces to be coated should be clean and dry. Remove peeling paint and brittle caulking. Heavy build-ups of asphalt roof cement should also be removed. Tighten any loose fasteners and replace those that are severely corroded. Repair or replace roof panels damaged by storms. Remove heavy rust with abrasive discs or wire brushes. Power-wash all surfaces to be coated and allow to thoroughly dry. Caulk all gaps wider than 1/16 inch that are not expansion and contraction slip surfaces.

Treating rusted areas

It is recommended that a corrosion inhibitive primer first be applied to areas where severe rusting has occurred. Liquid Rubber does not contain any corrosion inhibiting pigments but it is such an effective moisture barrier that it may be directly applied over light rust without a primer.

Going over existing coatings

[1] Original mill finish
When the original coating is still adhering tightly, it can be top coated directly with Liquid Rubber. Corrosion inhibitive primer should still be used on severely corroded areas.

[2] Alkyd paints
Aged alkyd paints that were applied over the original mill finish should be checked for adhesion. If coating is brittle and can be scraped off easily, it must be removed before Liquid Rubber can be applied. If removal can be accomplished with high- pressure water spray, that should be the method of choice. If removal is spotty, the roof should be allowed to weather another year before removal is again attempted. Brittle alkyd paint will continue to lose adhesion over time and will result in predictable failure if not removed.

[3] Asphalt based coatings
Liquid Rubber should not be applied directly over asphalt based coatings. Water based acrylic elastomeric coatings may be used as intermediate coats before applying Liquid Rubber. Asphalts should be considered as being unstable materials and are excluded from warranty coverage by Pro Guard Coatings.
Caution-Latex house paints cannot be substituted in place of the acrylic elastomeric coating.

[4] Acrylic elastomeric coatings
Liquid Rubber bonds very well to these coatings. Some of the earlier acrylic elastomeric formulations were prone to the development of under film corrosion. There usually is little visual evidence of this on the surface of the acrylic so small sections of coating must be removed from different parts of the roof to determine whether the condition exists and how severe it is. A visual inspection of the underside of the roof panels can reveal total penetration in the most severe cases.

The decision of whether to apply Liquid Rubber over an area with severe under film corrosion becomes an economic one. The recommendation should be to replace the corroded panels. However, if this is not an economically viable solution and removal of the coating is equally impractical, then application of the Liquid Rubber may be justified as being the best of the available alternatives.  No warranty would apply in such a case.

Application of Liquid Rubber

Airless or Air Atomized spraying is the only feasible application method for corrugated or standing seam roofs.  Airless equipment needs only one hose from pump to gun but must generate 3500-4000psi and is limited in the length of hose that can be used because of high-pressure drops. Air atomized equipment requires two hoses to the gun making it more cumbersome to maneuver plus the addition of a compressor.

Airless equipment specifications: 

PUMP Capable   of delivering 3-4 gal/min. at 3500-4000 psi
HOSE If 3/8   inch ID max. permissible length is 150 feet
when using .019 tipIf 1/2 inch ID max. permissible length is 200 feet when using .21 tip

Liquid Rubber will produce greater line drops and spray with narrower fan than most other coatings. Some solvent (xylene or mineral spirits) may be used to thin the product to make it spray easier. This dilution should not exceed 2 quarts solvent per 5 gallon pail. The recommended procedure is to spray apply and roll back with a short nap roller to obtain an even film and complete surface coverage. Application should be at rate of 40 square feet per gallon. This will produce a 20 mil dry film. The chemical and physical properties of Liquid Rubber make it possible to achieve a 20 mil dry film on sloped or vertical surfaces with one evenly applied coat.

Spray-on followed by rolling where surface configuration permits will produce an even film. Roller marks will level out in a few minutes.


Caulking around fasteners is usually not necessary. The physical properties of the EPDM rubber (Liquid Rubber) will produce a longer lasting seal around fasteners than caulks will because the latter will embrittle with age causing loss of adhesion and cracking.

It is good practice to brush the rubber into the fasteners after spray application to ensure complete coverage. This procedure will still be less time consuming than caulking.

Fabric reinforcing of seams and overlaps

Tight overlaps and standing seam joints do not need to be reinforced.

Overlaps with gaps greater than 1/16 inch and corroded edges should receive fabric reinforcing. Apply a light coat of Liquid Rubber, center the fabric on the overlap and roll it out taking care not to create wrinkles; press fabric down with squeegee or wide spatula; spray apply a full coat of Liquid Rubber to seal top surface of fabric and roll back over to ensure coverage.

Over spray

If over spray lands on cars, it can be easily removed with Mineral Spirits within 24 hours. Thereafter, stronger solvents such as Xylene will be effective in removing the rubber but may dull some finishes. Black, one-foot square test panels should be placed in various parts of the parking area as evidence of over spray in the event later claims are made.

Flushing Spray equipment

Three separate flushes with Xylene are recommended. (Save this solvent for future use).

When the last of the Liquid Rubber is sucked from the pail, add several gallons of Xylene to pail to purge material from line and onto roof. Remove gun from the hose and place end of hose in same bucket as pump suction. Reduce pump delivery pressure and allow solvent to recirculate for five minutes. Remove suction tube from bucket and purge line. Starting with clean solvent or the final flush from a previous cleaning, repeat the procedure two more times.

The gun can be reattached during the final flush for cleaning.

Pail handling and disposal

Pour material from newly mixed pail into the one from which the pump is sucking. Scrape the sides of the just emptied pail into the next one to be mixed. Only a thin film of material should remain. When this procedure is used, the pails can be collapsed and placed in a trash dumpster or taken to a metal recycler.

Rain showers or freezing temperatures.

Unexpected rain showers after application may affect the surface appearance but will not wash material off roof. Temperature drops below freezing will arrest the cure but will not damage Liquid Rubber. The cure reaction will resume again whenever adequate temperature returns.

Coating Spalled and Leached Concrete Roof Decks with
EPDM Liquid Rubber®
Proflex Flexible Epoxy®

Old concrete roof decks, which have not been coated or have a deteriorated coating, will experience degradation from water leaching and spalling caused by freeze-thaw cycles. This can result in moisture penetration leading to mildew, actual leaks and reinforcing bar corrosion. This structurally weakens the concrete which will not be remedied when only a waterproofer such as Liquid Rubber® is applied.

Pro Guard recommends that deteriorated concrete be first reconstituted with an application of Proflex Liquid Epoxy. This will seal and strengthen the surface enabling the Liquid Rubber to be more effective as a waterproofing coating.

Proflex can be used alone or mixed with sand to seal and fill small as well as large surface damage. The amount required would depend on the severity of the deterioration, which could be from 1 gallon Proflex per 100 sq. ft. to 1 gallon per 50 sq. ft.

Application Procedure

Dirt, algae, organic matter, loose paint and patching cements should be removed using a dry method such as wire brushing, brooming and a propane weed burner to kill algae. Roof should be dry before proceeding.

Mix small quantities of Proflex (1 gal) and start by applying material to cracks, craters and spalled areas. Add up to 70% sand for areas requiring more filling.

Next – mix 5-gallon quantity and pour a serpentine bead onto roof starting at furthest edge from roof access. Spread this material using a rubber squeegee and roller to cover an area of 250-500square feet per 5-gallon pail. Add more product to areas absorbing the initial application until entire surface has a uniform appearance.

Allow an overnight cure.

Liquid Rubber may be applied even if Proflex is slightly tacky. Spread rubber at a rate of 40 square feet per gallon.

The above-described procedure will result in an average coating thickness of 40 mils (equivalent to 10 sheets of copy paper).

Coating Wood
Liquid EPDM Rubber

All wood whether in board or plywood form has surface porosity the degree of which varies only with the species of tree it came from.  In order to obtain a uniform appearance when Liquid Rubber is applied to a wood surface it is necessary and cost effective to first prime the wood with a solvent based paint.  This seals the pores in the wood and enables the rubber to form a smoother and more aesthetically pleasing appearance.

Solvent based paints are preferred to water types because they penetrate better and therefore produce better adhesion on wood.  ALKYD type paints or Pro Guard’s Proflex Flexible Epoxy products are recommended for this purpose.


The wood to be coated should be dry and free from mold and mildew.  Splits should be filled with a BUTYL CAULK which should then be allowed to cure for at least three days prior to priming.


Apply a solvent based Alkyd or Proflex Primer at a rate of approximately 150 square feet per gallon.


Wait until morning dew has dissipated before starting.  Add catalyst by following directions on container.  The pot life of the rubber after adding catalyst will be 4-6 hours depending on temperature.  The method of application can be by brush, squeegee and roller or airless spray.  The rubber may be diluted with Xylene or Mineral Spirits to suit the method of application.  If the rubber is applied at the rate of 35 square feet per gallon a 25 mil dry film will result.  (equivalent to 5 sheets of copy paper)

Thicker dry films are possible on flat surfaces in one coat by simply applying more rubber coating.  Multiple coats may be applied to vertical or sloped surfaces.  The intercoat adhesion will be better if the interval between coats is two to three days.

The information presented herein is furnished free of charge and is based on technical data that Pro Guard believes to be reliable. It is intended for use by persons having technical skill and is at their own discretion and risk. Since conditions of use are outside our control we make no warranties, express or implied, and assume no liability in connection with any use of this information. Nothing herein is to be taken as a license to operate or a recommendation to infringe any patents.

Application Tips for Contractors

Liquid Rubber
F9981 White
F9988 Gray
F9999 Black
F9961 Low VOC

Liquid Rubber® is a two component solvent solution version of the single ply EPDM membrane rubber.  Its physical properties and method of cure make it unique among liquid applied coatings.  The unique combination of properties of Liquid Rubber® include:

  •  Can apply an up to 35 mil dry film in one coat.
  •  Penetrates into cracks and crevices.
  •  Can go directly over a lightly rusted surface without a primer.
  •  Cure is not affected by relative humidity.
  •  Freezing does not damage uncured coating.
  •  Can withstand ponding water or immersion indefinitely.
  •  Tolerates a wide temperature range from -60°F to 300°F.

Liquid Rubber® has application and spray characteristics that are considerably different from other types of liquid coatings.  Although Liquid Rubber® has a heavy consistency, it will self level and penetrate small crevices and pores.  It is also harder to brush and more difficult to atomize for spray.  The two efficient methods of application are:

For Flat Surfaces (flat or low slope)

First, catalyze the rubber: Pour a quantity on the surface and broadcast with a rubber edged squeegee.  Follow this with a short-knap roller (lint free mohair) to evenly distribute the wet film.  Spread rubber at no more than 45 sq.ft. per gallon.


A.) Equipment: Use a 3.0 gallon per minute airless spray pump capable of developing a minimum 3,000 psi outlet pressure; 3/8 inch ID hose or larger with a max length of 100 ft.  Tip size of .015 or .017 for smaller pumps and a .019 tip for larger capacity pumps.  Use a 100-mesh strainer at the outlet of pump or in handle of gun.  Use a swivel fitting at the gun in place of a “whip” in order to reduce the pressure drop through a smaller ID hose.

B.) Thinning: It will be necessary to thin Liquid Rubber® with xylene solvent before it can be sprayed.  The amount of xylene needed will vary depending on pump size and material temperature.  The following is a recommended starting point procedure for thinning a 5-gallon pail:

1.) Add one gallon xylene to pail and mix until uniform.

2.) Add entire amount of catalyst supplied. Mix thoroughly.

3.) Transfer ½ contents to another pail.

4.) Start pump and check spray pattern. If spray is too coarse try a .015 tip.  If this still isn’t enough improvement, then add another quart of xylene to the 2½ gallons of rubber in the pail.

Once an acceptable spray pattern is achieved, use the same amount of xylene to dilute each succeeding pail.  Pour newly mixed rubber into pail under the pump as needed.

Troubleshooting Procedure

Poor spray pattern and clogging of the tip are the most frequently encountered problems during application.  These can invariably be traced to inadequate flushing and poor maintenance of the equipment.  Check to make certain the 100-mesh strainer is clean before starting.

Problem: Poor spray pattern.

Solution: Follow thinning procedure in section B.

Problem:  Still getting a poor spray pattern, even after thinning rubber with 1½ gal of xylene per 5-gallon pail.

Solution:  Starting at gun, successively remove one component at a time, (i.e. tip, tip extension, gun filter, gun, strainer at pump, etc.) and check flow.

With tip removed, the material flow should be steady and strong (discharge into pail at pump.)

If tip extension is removed and flow increases noticeably, the ID of the extension is too small. Remove or replace.

If discharge stream is weak and pulsating, attach gun and open drain cock at strainer to see if condition is the same there.  If pulsation persists, the problem is in the pump. (The balls are not seating properly or are dented and need replacing.)

How to Achieve Minimum Dry Film Thickness

Liquid Rubber® must be applied at a rate that will produce a minimum dry film of 20 mils.  This can be accomplished in one coat by applying the rubber at a rate of 200-220 sq.ft. per 5-gallon pail if undiluted.  (6 or 6½ gallons when thinned with xylene.)  The actual (expanded) surface area must be used for this calculation.


If expanded area of a ribbed or standing seam roof is 1.2 times the length and width area calculation and 1.5 gallons of xylene thinner was used per 5 gallons of rubber, how much material will a 3,000 esq. roof require?

3,000 sq.ft. X 1.2   = 3,600  =  16.36 pails X
5 gal = 82 gallons

220 sq.ft./pail            220                                      undiluted

16.36 pails  X  1.5 gal xylene/pail =                       + 24.5 gal xylene

106.5 gal
diluted rubber

Spread Rate

The spread rate of 220 sq.ft. expanded area per 6.5 gallons of diluted rubber (5 gal rubber + 1.5 gal xylene) is adjusted to the length X width roof dimension.

220 = 183 sq.ft of roof area (L X W) therefore:


When 6.5 gal of diluted Liquid Rubber® are applied to 183 sq.ft. (L X W) of roof, an average dry film of 20 mils will result.

Coating Interaction of Liquid EPDM Rubber and Water Based Elastomeric Coatings

Because water based Elastomeric coatings are not solution products they form films which breathe.  This means that moisture vapor can pass through the film without causing blisters.  This also indicates that Elastomeric films have permeability which then can allow vapor to pass through the film in both directions.  The latex solids that form the film will also swell and shrink with changes in moisture.  It is the latter feature which results in adhesion failures of Elastomeric films especially on flat and low sloped surfaces.

Thicker Elastomeric films (i.e. multiple coats) will have proportionately lower permeability and therefore be a more effective moisture barrier.  Most Elastomeric Coating Manufacturers recommend (some even specify) that multiple (3) coats be applied and nearly all caution against ponding water.

Liquid EPDM Rubber on the other hand is a solution product with hydrophobic (water shedding) properties.  This enables the coating to easily withstand ponding water or total immersion.

It would seem logical then from the above description that if Liquid Rubber were applied over the Elastomeric it would overcome the latter’s shortcomings.  This procedure however will only work under certain conditions as described below.

DO NOT apply Liquid Rubber over Elastomeric on:

Flat roofs or roofs with slopes of 3” per foot or less regardless of the type of roof.  (asphalt, membrane, metal)

Alternate Solution;

a)   For asphalt built up roofs – best solution is to apply EPDM membrane sheet on top.

b)    For low slope metal roofs (3” per foot or less) remove elastomeric using high pressure water spray and re-coat with Liquid Rubber.  Or – apply several more coats of elastomeric if original coat is still tightly adhered.

NOTES:  No warranty would apply if elastomeric looses adhesion.  Customers should be made aware that this is a possibility.  Pro Guard does not offer an elastomeric product and is only providing cautionary information here.

Situations where Liquid EPDM Rubber can be applied over an Elastomeric:

Metal roofs with slopes of 3” per foot or more:

The elastomeric can be topcoated if it is still tightly adhered.  However there is still a risk that the Elastomeric will lose adhesion on some portions of the surface.  This can be addressed with spot repairs.


1)   Elastomeric coatings should not be used on flat or low sloped roofs.

2)   Thicker elastomeric films perform better than a single coat topcoated with Liquid Rubber.

3)   Liquid Rubber “can” be used with success on many things but still would not be covered under the warranty.

4)   Our warranty provides coverage when applying Liquid Rubber to a sound substrate, not a coating.

Manual Application Procedures for EPDM Liquid Rubber®

EPDM Liquid Rubber® can be applied directly on many types of substrates that have solid, stable, non-porous and uniform surfaces such as flat roofs.  For most substrates, primers are not necessary.  As an example, some types of substrates that can be coated with EPDM Liquid Rubber® are:

–        EPDM Rubber Sheet Roofs
–        Galvanized Steel Panel Roofs
–        Non-Polished Aluminum Sheet Roofs
–        Steel Plates (Painted, Unfinished, Light Rust)
–        Fiberglass Roofs
–        Wood & Plywood (treated with oil based sealer)
–        Non-porous / troweled concrete surfaces / masonry


Work on days when rain is not expected and in temperatures of 65° to 75° F. for comfort.  The curing process requires an ambient temperature above 55° F.  A full cure will be achieved in 4 to 10 days after application, in consistent 70° F. ambient temperatures.  Higher temperatures will accelerate cure times and lower temperatures will extend cure times.  Although EPDM Liquid Rubber® will immediately waterproof, avoid heavy rain until dry to the touch (16 – 20 hours after application).  Pitting may occur otherwise.

Pre-Application Inspection of Roofs / Surfaces to be coated

Inspect your roof surfaces for structural damage, tears, leaks, gaps, corrosion, etc.  Light surface rust if adhering well to the roof surface can be either lightly sanded or left in place.  Heavy rust should be removed and a good corrosion inhibitor / primer should be applied – check with the manufacturer and wait for the recommended dry time before applying EPDM Liquid Rubber® over these areas.  Any holes, gaps, tears or lifting or separating seams, should be repaired or reinforced prior to application of EPDM Liquid Rubber®.

Surface Preparation

After inspection and repairing any existing damage, all asphalts or silicone type of caulking on the roof / surface, should be removed.  Asphalt products are not compatible with EPDM Liquid Rubber®.  In instances where it is difficult to completely remove asphalts, consider covering with a substantial barrier, such as plywood, metal plates, etc., and then apply EPDM Liquid Rubber®over this barrier.

Glossy and slippery finishes such as polished steel and metal surfaces should be abraded to provide a “rougher” finish to the surface to promote adhesion.  Some surfaces like polished stainless steel, silicone rubber, PVC and other plastics may have poor adhesion to EPDM Liquid Rubber®, and should be avoided.  When in doubt, try a test sample first, and / or consult Pro Guard Coatings Technical Services Department.

Prior to coating, thoroughly clean and wash the surface with detergent and water, ensuring the surface is free of oils, dirt, debris and flaking paints, etc.  If the surface has fungus, mold, mildew, or algae, you may need to soak these areas in a 1/3rd bleach and water solution to kill them.  Let soak until the solution evaporates.  You will need to scrub (with a stiff brush) the affected areas with soap and water after soaking with the bleach solution, as some biologicals may anchor onto the surface, and must be mechanically removed even after killing.  After cleaning, allow the roof to dry thoroughly prior to applying EPDM Liquid Rubber®.

When applying over wood / plywood, use an oil base primer first.  Our EPDM Liquid Rubber® can be directly applied over EPDM Rubber Sheets with little preparation other than cleaning as above.   It is recommended, however, that forlarger and older projects you use our Surface Conditioner F9910 prior to application of our EPDM Liquid Rubber®.  Surface Conditioner F9910 was formulated to promote better adhesion on EPDM Rubber Sheets when a thorough cleaning is not practical.

With masonry / concrete, the surface to be coated must be relatively smooth (steel troweled) and uniform (not honey-combed, full of imbedded stones or aggregate breaking the surface, etc.).  The surface must be structurally stable, dry, non-porous, and free of oils, debris, and flaking or loose paint.  New (green) concrete may need to be aged 30 days or longer to dry moisture content adequately – check with the concrete supplier for aging recommendations.  Fill any cracks, or spalling or other surface defects on the concrete surface with Proflex Flexible Epoxy® or Butt Putty® Crack Filler to level and smooth out the surface.

The “porosity” of concrete / masonry can be somewhat subjective and needs to be addressed prior to applying EPDM Liquid Rubber® on such surfaces.  When in doubt and when time permits, prepare the surface as above and apply a 20 mils dft coat of EPDM Liquid Rubber®to a test section. Check when cured in about 4 to 10 days, for surface “bubbling” and adhesion.  Bad adhesion and “bubbling” indicates that the structure is too porous.  In such a case, or when testing times do not permit, it is recommended you apply a coat of Proflex Flexible Epoxy®on the concrete first, to “fill in the pores”, let dry, and then apply the EPDM Liquid Rubber® over the Epoxy, as per these instructions.

Applying EPDM Liquid Rubber®

The Supplies you will need are:

1-    An electric drill (not cordless)
2-    A paddle mixer for a can or pail.
3-    A rubber squeegee attached to a mop or broom handle.
4-    A ¼” short nap roller attached to a mop or broom handle.
5-    A paint brush
6-    A rubber spatula
7-    Xylene for clean up
8-    Rags

Using mop or broom length handles for the squeegee and the roller will allow you to apply the product standing up and not on your knees.  Use the paint brush for hard to reach areas.  Broadcast & spread using the squeegee. Use the ¼” short nap roller to smooth out trapped air and even out the EPDM Liquid Rubber®.  Unwanted splatters and drips can be cleaned off with rags and xylene or mineral spirits when wet (within 4 hours of application).

It is important to apply an even coat of EPDM Liquid Rubber® at the correct thickness.  Not enough material will produce a membrane that is to thin with inadequate adhesion and poor film strength.   Too much material will be wasteful, will cause long or no cure conditions and may cause excessive swelling with some types of sheet rubber roofs.

The optimum thickness for most purposes is one coat of 20 mils dft.  To achieve a 20 mils dft. thickness, you should do a spreading rate calculation.  For fairly smooth surfaces such as EPDM sheets, un-polished metals, fiberglass roofs, etc., use a spreading rate of about 40 sq.ft. per gallon.  Reduce this for rougher surfaces such as steel troweled concrete, use a spreading rate of about 30 sq.ft. per gallon.  When calculating applied surface area, ensure you measure true surface areas.  Example; if a roof is corrugated; take into account the corrugations in calculating the surface area.

If you have not applied EPDM Liquid Rubber® before, we recommend you apply this in several pre-measured sections.  For the first section, apply 1 gallon, over a 40 sq.ft. section.  By applying 1 gallon over this 40 sq.ft. area, you will form a 20-mil dft. thickness when cured.  The key is to spread the product evenly.  In 75° F to 85° F, the product will start to thicken up in about 4 hours, so you should plan your work with that in mind.   This first gallon should not take you more than an hour, but it will give you an idea of how fast you can work. On subsequent sections, you may choose to use more material if you feel comfortable applying the product.

1-When ready to apply the first gallon, follow the mixing directions on the can.  Using an electric drill with a mixing shaft, run the shaft in the gallon of EPDM Liquid Rubber®until a vortex forms.  Pour the pre-measured catalyst into the vortex and let the drill run for about 15 to 20 minutes to thoroughly mix the EPDM Liquid Rubber® with the catalyst.  Be sure to scrape the sides of the can with a rubber spatula in order to incorporate all of the material.  The catalyst is in a plastic bottle and is bluish-purple in color.

2-Pour the catalyzed EPDM Liquid Rubber® onto the pre-measured 40 sq.ft. area in a serpentine line.  Use the rubber squeegee to quickly spread the product over the 40 sq.ft. as evenly as you can.  Again, it is stressed that an even application is important.

3-Use the short nap roller to promote a more even distribution of product and to get trapped air bubbles out.  After spreading with a squeegee, go over this area with the roller in slow long even strokes. Do several strokes with the roller to get an even and bubble-free application.  Use a paintbrush for nooks and crannies and areas where using a roller may be difficult.

You may initially see some roller / brush strokes. EPDM Liquid Rubber®, however, is self-leveling and these roller / brush strokes will level disappear if enough material has been applied.

By applying an even thickness of 1 gallon of EPDM Liquid Rubber® on a 40 sq.ft. pre-measured area, you are ensuring the correct dry film thickness is achieved.  When applying the next section, overlap an inch or two and blend in the overlap so you have a continuous and seamless membrane when cured.

In 70° F., the applied EPDM Liquid Rubber® will be dry to the touch in about 16 to 20 hours.  This will still not be fully cured, but you should be able to walk on the roof / surface.  In these temperatures, your newly applied EPDM Liquid Rubber® Roof will be fully cured in about 4 to 10 days.  Higher temperatures will accelerate the curing time and, lower temperatures will prolong the curing process.

On some materials, such as EPDM rubber sheets, some swelling may occur due to solvent absorptions after applying EPDM Liquid Rubber®.  This is normal.  This swelling will recover with time and heat.  In 80° F or so, allow 7 to 14 days to recover.  In colder temperatures, recovering will take several weeks, as much as 6 to 8 weeks in 60° F.

Applying EPDM Liquid Rubber® too thick in a single application will cause excessive swelling and longer recoveries, thick single coat applications should be avoided.  Overly thick applications will take too long to cure, and may not cure in the center.

You will also be able to coat over cured existing EPDM Liquid Rubber® years after the first application.  Clean and dry the surface as described above under Surface Preparation.  No primers are necessary when recoating over EPDM Liquid Rubber®.

Liquid EPDM Rubber Coatings
Performance and Applications


EPDM is a synthetic elastomer made by combining ethylene and propylene with a diene monomer attached. This polymer (when crosslinked) is a very good moisture barrier, resistant to oxidation and UV degradation but its most important property is its ability to tolerate both low as well as high temperatures ( from minus 62 to plus 350 degrees Fahrenheit ). EPDM rubber is used exclusively for radiator hoses, freezer gaskets and low temperature seals, steam hoses, and rubber roofing membranes. It is also blended with other rubbers to improve their properties. A multitude of products are now better and last longer because of the contribution made by EPDM rubber.

EPDM Rubber Coatings

Liquid EPDM coatings require a lower molecular weight polymer than is used in the molded products mentioned above. But the other and even more important requirement is the ability to cure at ambient temperatures. Pro Guard Coatings began development work on liquid EPDM coatings in 1990 and launched the first commercially available EPDM coating the following year. Numerous incremental improvements were made over the next several years but the most significant improvements resulted after the discovery of several new catalysts. The products now cure faster, produce better film properties, meet the California VOC restrictions, do not need special hazard labeling, have excellent storage stability, and are environmentally friendly.

How does EPDM rubber compare to other coating types?

Water resistance……………………..    EPDM is better than epoxies, urethanes, acrylics,   Polyesters and alkyds at equal film thicknesses  and is not affected by continuous immersion.

UV resistance…………………………    Equal or better than acrylics, polyesters and  Urethanes; much better than alkyds and epoxies.

Temperature tolerance…………….    EPDM is better than all other coating polymers except Silicones. EPDM can withstand live steam as well as cryogenic temperatures.

Flexibility…………………………EPDM is better than all other coating polymers except Silicones. EPDM can withstand live steam as well as cryogenic temperatures.

Chemical Resistance………………… EPDM has very good resistance to strong alkali’s, concentrated salt solutions, many acids, alcohols and polar solvents such as ketones.  EPDM has poor resistance to oils, fats, waxes and hydrocarbon solvents.

Surface tolerance………………………. EPDM coatings will not bond to a surface which is damp with moisture but will bond to an oil or wax contaminated surface.  EPDM coatings can also be applied directly to metal surfaces which have tightly adhering corrosion without a primer.

Where can EPDM coatings be used to their best advantage?

The unique combination of properties which EPDM coatings possess can be best utilized when they are applied to the exterior surfaces of stationary structures.  Examples are:

Roofs……………………………………….. Metal, rubber or thermoplastic membrane, fiberglass, urethane foam, cement tile and plywood.

Metal Siding…………………………….. can be applied with little or no surface preparation as a one-coat finish on steel buildings.

Concrete Tanks…………………………. The excellent water proofing properties of EPDM will reduce or prevent spalling of the concrete in cold climates.

Corrosive/Humid Environments…. Exposed structural steel on the interior of industrial buildings with humid or corrosive environments can be coated with minimal surface preparation.  Plating operations, smelters, concrete casting operations, dye works, and paper mills are just a few examples.  High density poultry and hog production operations are another good use to protect steel from the corrosive environment produced by manure.

Impoundments………………………….. Liquid EPDM coatings are a good choice for exterior spill containment structures because of their excellent weathering and broad chemical resistance properties.

Ponds and Fountains………………….. concrete fish ponds, fountains and reflecting pools are another good application for EPDM.  These are demanding applications where the unique properties of EPDM have a distinct advantage over other products.

Unsuitable applications for EPDM Coatings

The relatively slow cure and non aggressive adhesion of EPDM coatings make them poor candidates as factory applied finishes or as coatings for products which come in contact with each other during shipment or use. They are also not recommended for environments where they could be exposed to oils, fats, waxes or liquids with similar characteristics.

The information presented herein is furnished free of charge and is based on technical data that Pro Guard believes to be reliable. It is intended for use by persons having technical skill and is at their own discretion and risk. Since conditions of use are outside our control we make no warranties, express or implied, and assume no liability in connection with any use of this information. Nothing herein is to be taken as a license to operate or a recommendation to infringe any patents.

Procedures for coating Ponds
with EPDM Liquid Rubber®

Having a good understanding of a material’s characteristics is important in order for you to be successful when coating your pond.

EPDM Rubber is a great barrier to water, tolerates temperatures from –62° to +350°F, is stable to UV exposure from sun, and WILL SWELL when in contact with OILS, FATS, WAXES and non-polar SOLVENTS such as Mineral Spirits.

The below procedure will prevent swelling at the edge of the pond and when done carefully should provide a long lasting seal.

When EPDM liners are used in a pond setting they should be installed well over the top edge of the pond so the decorative rocks can be placed on top of the liner.  This procedure eliminates most of the problems encountered when different materials are used in an attempt to create a seal between the membrane and the pond wall, which is often complicated by the presence of the decorative stones.

The top three inches of the membrane must first be glued to the pond wall by either using the liquid adhesive recommended by the membrane manufacturer or utilizing the “IN SEAM TAPE” (we sell it as Butyl Tape).  The tape is easier to use in warm weather and the adhesive is easier to use in colder weather.  Clean the membrane by wiping it with rags soaked with paint thinner.  The type of thinner is not critical – you mainly need to remove the talc that is used to keep the rubber liner from sticking to itself.

The next step is to encapsulate the exposed edge of the membrane and prevent the weather from undoing the seal.  This is the most critical part and must be done properly.

1)   Clean four inches at the top of the membrane by wiping with solvent.

2)   Create clean surfaces on the masonry and rocks by removing all dirt and loose material.  Allow to dry.

3)   Coat cleaned masonry and membrane with a light coating of contact cement.

4)   Cut 12-inch lengths of Butyl Tape and apply by centering over the membrane’s edge.  Press tape against membrane first and then toward flat masonry surface.  Roll repeatedly with a 2” wooden wallpaper roller for good adhesion before removing release film.  Repeat until edge is covered.  A second overlapped layer may be added.

5)   Coat Butyl Tape plus 1” beyond on membrane as well as masonry edges with F9911 Liquid Rubber Sealant.  A topcoat of EPDM Liquid Rubber® in F9981 White, F9999 Black or F9988 Gray can be applied the following day.

Repairing Pond Liners
with Liquid Rubber

When repairing pond liners it is important to prevent puncturing the liner by walking on it.  Use Styrofoam with plywood on top to stand on.

If seam on liner is not delaminated you can simply wipe the area with a rag wet with Xylene solvent and coat with Liquid Rubber.

Where seam is delaminated:

a)   Apply a thin layer of contact cement with brush.

b)   Apply 3” wide strip of Butyl adhesive tape (can be ordered from Pro Guard) and roller over it to get a good contact.

c)   Remove release film and apply 3” strip of polyester fabric to reinforce adhesive tape.

d)   Coat entire repair with Liquid Rubber.


Materials Required:

3” Adhesive Tape (Seam Seal Tape)

3” Polyester Fabric

Liquid EPDM Rubber


1)  Clean 6” wide strip of seam using a combination of stiff brooming & wiping with solvent soaked rags.

2)  Prime cleaned area with Tape Primer (Firestone or Mule Hide) or Pro Guard Surface Conditioner.

3)  Apply adhesive tape leaving release film attached.  Roll tape to improve adhesion.

4)  Remove release film and apply 3” wide polyester fabric.

5)  Coat approximately 5” to 6” width (1 – 1 ½” beyond tape) with Liquid Rubber.

Material Requirements:  Estimate is per 100 lineal feet of seam.

Adhesive Tape

100’ of tape per 100’ of seam.

Polyester Fabric – Comes on a roll 3” wide x 180’

Use 100’ of tape per 100’ of seam.

Liquid Rubber

Assume a 6” wide application per lineal foot of seam = 50 sq. ft. to be coated per 100’ of seam.

Spraying EPDM Liquid Rubber®

Liquid Rubber can be sprayed using airless equipment. Choosing the proper equipment, however is key to achieving satisfactory results. The fluid characteristics of Liquid Rubber produce considerable pressure drop in the hose so pump size hose diameter and total length of hose must be chosen carefully in order to achieve satisfactory results.

The following recommendation is for Graco equipment. Other manufacturers with comparable pumps may also be used.

Liquid Rubber must be thinned with solvent to achieve a sprayable viscosity. See recommendations below.

Equipment capable of spraying Liquid Rubber

Pump Model Max.
Graco GH733 3500 psi 3.0 gpm 1/2 inch 150 feet
Graco GH3640 36000 psi 3.8 gpm 1/2 inch 150 feet
Gun Should be rated for spraying mastics. A 30-40 inch tip extension is recommended
Tip Size  .017 to .021 with a 12 inch fan width

Note: Do not use a “whip” between hose and gun. This reduces flow and pressure which results in poor atomization.

Thinning Liquid Rubber

The “as shipped” viscosity of Liquid Rubber is 34-37,000 cp which is too high for spraying. By adding one gallon of Xylene Solvent to a 5 gallon pail the viscosity drops to 10,000 cp at 75° F. More solvent may have to be added at lower temperatures.

The spray atomization can be improved using a smaller tip size or adding more solvent to reduce viscosity.

Wash solvent from previous pump cleaning can be used for thinning after it is strained to remove dirt.


Caulking around fasteners is usually not necessary. The physical properties of the EPDM Liquid Rubber will produce a longer lasting seal around fasteners than caulks will because the latter will become brittle with age, causing loss of adhesion and cracking.

It is good practice to brush the rubber into the fasteners after spray application to ensure complete coverage. This procedure will be less time consuming than caulking.

Fabric Reinforcing of Seams and overlaps

Tight overlaps and standing seam joints do not need to be reinforced.

Overlaps with greater than 1/16” or corroded edges should receive fabric reinforcing.

• Apply a light coat of Liquid Rubber.

• Center the fabric on the overlap and roll it out taking
care not to create wrinkles.

• Press the fabric down with a squeegee or wide spatula.

• Spray a full coat of Liquid Rubber to seal top surface of the fabric.

• Roll back over with a short nap roller to ensure complete surface coverage.


Overspray can travel a long way when carried by a breeze. Vehicles should not be parked downwind near the work area. Overspray landing on a vehicle can be easily removed with Mineral Spirits even after 24 hours. Thereafter, stronger solvents such as Xylene will be effective in removing the rubber but may dull some finishes.

Rain Showers or Freezing Temperatures

Unexpected rain showers after application may affect the surface appearance but will not wash the material off the roof. Temperature drops below freezing will arrest the cure but will not damage the Liquid Rubber. The cure reaction will resume again whenever adequate temperature returns.

Cleaning Equipment

A three stage flushing is recommended.

1.  Add Xylene on top of the remaining rubber in pail and continue pumping until Xylene reaches gun. Reduce pump pressure; add 2-3 gallons of Xylene to pail and spray into pail. with tip removed for about 30 seconds. Then remove gun and recirculate solvent for 3-4 minutes. Tilt pump out of solvent and let air pressure purge the material in hose.

2.  Put clean pail with clean Xylene under pump and circulate at low pump pressure 3-4 minutes. Connect gun without tip for another short flush, then remove gun. Again tilt pump out of solvent, let air pressure purge the line.

3.  Put another bucket with clean solvent under the pump and circulate for 3-4 minutes. The solvent should be a little stained by now. Connect gun with tip and spray about 10 seconds with rag over the tip.

The equipment is now ready for the next use. If work is to continue another day the solvent can remain in the line if gun is attached. Clean up solvent should be strained and used for thinning as application continues.

On some materials, such as EPDM rubber sheets, some swelling may occur due to solvent absorptions after applying EPDM Liquid Rubber®. This is normal. This swelling will recover with time and heat. In 80° F or so, allow 7 to 14 days to recover. In colder temperatures, recovering will take several weeks, as much as 6 to 8 weeks in 60° F.

The information presented herein is furnished free of charge and is based on technical data that Pro Guard believes to be reliable. It is intended for use by persons having technical skill and is at their own discretion and risk. Since conditions of use are outside our control we make no warranties, express or implied, and assume no liability in connection with any use of this information. Nothing herein is to be taken as a license to operate or a recommendation to infringe any patents.

Structural Designs that Result in Failure of Liquid EPDM Rubber Applied Directly to Plywood

Plywood is fabricated using multiple layers of thin wood bonded together with glue.  The middle or filler layers are usually soft pine with outer layers of Spruce or Fir.  The wood will swell and shrink with changes in moisture which can cause delamination of the layers when remaining wet.

Liquid EPDM Rubber has a hydrophobic surface characteristic which make it a very good barrier against water.  However, if a plywood substrate becomes wet as a result of condensation or leaks.  This hydrophobic surface also acts to separate itself from the wet wood.

Design Flaws

Quite often, when home owners add a room or two they opt for a simple box design with a flat roof.  The plywood deck will invariably be fastened to the top of the roof joists and the space between the insulation.  There will either be insufficient or no air space between the insulation and the roof deck and no or insufficient vent openings to the outside to allow moisture to escape.

During cold weather the relative humidity will be considerably higher inside than outside the house.  This will drive some moisture into the roof area where it will condense as it encounters the dew point between the insulation and the deck.  If ventilation is deficient the condensate will accumulate and result in delamination and rotting of the wood.

Had Liquid EPDM Rubber been applied directly to the plywood with this flawed construction it would fail relatively quickly and possibly result in structural damage before the failure is detected.

Guidelines for coating Plywood with Liquid Rubber

Do not use Liquid Rubber direct to plywood on any roof, whether flat or sloped, over a heated living space.

Liquid Rubber may be applied direct to primed plywood (oil based primer) on small utility and garden sheds and garages which are not insulated or heated and the roof has a slope of 30° or more.  The joints between panels must also have a bridging seal such as Butyl Tape.


1)  Catalyst must be added prior to use.  Scrape sides of container with a rubber spatula to ensure catalyst distribution.

2)  Xylene or Mineral Spirits Solvents may be added to adjust viscosity or for clean-up.

3)  Easiest way to spread the rubber on a flat surface is to broadcast material with a rubber squeegee then roll using a short nap roller.  Product is self leveling.  A flat spatula can be used for small areas.

4)  Product has a long pot life after catalyst has been added; 4-6 hrs. depending on temperature.

5)  Only temperature affects the rate of cure.  Relative humidity has no influence.

6)  Product is hydrophobic (sheds water) so substrate to be coated must be dry initially.  The uncured rubber can get wet or even have ponding water, with only a cosmetic effect after application, and will still cure.

7)  The rubber will penetrate into porous substrates such as wood and poured concrete.  A primer/sealer should precede application of rubber.


This Universal Repair Method
can be used on:

*Sheet Rubber       *Metal       *Automotive       *Vinyl

*Masonry       *Fiberglass     *Fish Ponds       *Fountains

*Thermoplastic Membrane



*Scissors are best for cutting Butyl Tape

*Always cut Tape with release film attached

*Wet the blades with paint thinner to prevent Tape from sticking

*Wet fingers with paint thinner when handling Tape without release film attached to prevent sticking

*Use needle nose pliers to remove release film when working in confined spaces

*Use a wooden or metal roller to press tape to surface for better adhesion

*Tape can be overlapped to cover a wider area

*Always reinforce Tape with Fabric to eliminate stretch


• Clean substrate and underside of part with paint thinner.

• If surface temperature is cold heat with a hair dryer until barely warm to the touch.

• Cut Butyl Tape to approximate size of part and lay it on a flat surface with the sticky side up.

• Press part onto Tape and trim excess with scissors.

• Remove release film.

• Lay part into place starting at one side to avoid trapping air bubbles and press onto surface for better adhesion.


• Cut convenient size pieces of Tape and slide under loose membrane with release film attached.

• Start at one end and successively remove the release film while gently pressing membrane onto tape.

• Roll surface for better adhesion.


Surface Prep:

Metal, Fiberglass, and Masonry
Use a wire brush or sandpaper to clean surface and create a slightly rough surface.  Then wipe with paint thinner.

Rubber and Thermoplastic Membrane
Remove surface chalk by wiping repeatedly with rag wet with paint thinner.

• Center the Butyl Tape over the seam and press onto surface with a solid roller.

• Do not remove release film until ready to apply Fabric.

• Remove a section of the release film and center the rolled Fabric over Tape and press onto Tape.

• Alternately remove more film and roll out Fabric until all Tape is covered.

• Use roller to firmly embed Fabric to Tape.

• If Fabric begins to go off center cut it and realign.

• Topcoat the reinforced Tape with Liquid Roof® or EPDM Liquid Rubber® plus 2 inches beyond to complete the repair.


This product will perform as claimed if directions are followed. Since we cannot control the conditions or methods of use, our warranty is limited to replacement or refund value of the product actually used. This warranty does not include labor or labor costs. Performance warranties are available through certified applicators.