Spray Liquid Rubber on metal
Only true EPDM in Liquid form in the World
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Liquid Rubber Spray Application

What do you want to spray with liquid Rubber?

We have five different liquid rubbers each one the best for different applications. EPDM is best for old metal roofs and old EPDM roofs or protecting iron and steel anywhere. But there is also a clear rubber for invisible protection and others for ponds, flat roofs, skylhits and georgian glass, grp, motorhoem and caravan roofs ...

If you want to protect an old EPDM or steel roof or other steel and iron structure then read on. If your project is something else, contact us for advice on the best rubber and what you need to spray it.

Liquid Rubber EPDM sprayed on old metal roofs is probably the quickest and best way to give you a long lasting weatherproof roof protected from corrosion. What is great, is that it requires minimal preparation, no primer and just one coat of the liquid rubber.

EPDM is almost unique for a roof coating becuase it is not only waterproof but it is a vapour barrier. This may not sound interesting, but it menas that no moisture can get to the metal substrate so it stops corrosion dead in it's tracks. Many coatings boast about breathability but, on metal, you do not want that two way street of moisture vapour.

Choosing the right equipment for the job is important if you want to achieve a satisfactory finish. The fluid characteristics of the EPDM Liquid Rubber produce a considerable pressure drop in the hose - so pump size, hose diameter and the total length of the hose must be chosen carefully. Liquid Rubber must be thinned with solvent to achieve a sprayable viscosity. See recommendations below.

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

Equipment capable of spraying Liquid Rubber EPDM

Pump Model  Max. Pressure  Fluid Flow Hose ID Max. Hose Length
Graco GH733 3500 psi 3.0 gpm 1/2 inch 150 feet
Graco GH3640 3600 psi 3.8 gpm 1/2 inch 150 feet
Roof Rig  
Gun   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 EPDM

Liquid Rubber EPDM in its 'as shipped' form has a viscosity of 34-37,000 cp, which is too high for spraying. The viscosity of the material drops to 10,000 cp at 23.8 °C / 75°F if Xylene solvent is added at a ratio of one US gallon to every 5 US gallons of Liquid Rubber EPDM. If the temperature is lower than 23.8 °C / 75°F then more solvent may have to be added.

The spray atomisation can be improved by 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 we believe 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.