Installing Silicone Roof Coatings to Spec

STEPS TO FOLLOW WHEN INSTALLING SILICONE ROOF COATINGS

Installing silicone roof coatings is an extremely simple process. It is well-documented on this blog, the ease with which one can install silicone. However, while the process is easy, there is some variation from one substrate to the next in how the coating must be installed. In a few instances, a primer is required, in others it is not. In a few instances, you’ll have to use fabric on the seams, in most you will not. This post will give you a quick rundown of the major variations between specs for our system. If you’d like a more detailed review, check out our Installation Overviews or full-on Product Specs here. Please note that the specs below do not guarantee warranty receipt, they are general guidelines. 

Installing Silicone Roof Coatings over Single-Ply (PVC, TPO, Hypalon)

Single-ply substrates are a great application for silicone roof coatings. These membranes were one of the original substrates to be restored with silicones. Single-ply stays structurally sound, even when it may begin to leaks, so they are a great candidate for silicone. There are two primary limitations to restoring single-ply with silicone: 

1. An oily film is typically present on top of the membrane for the first ~5 years of service. Silicone adheres to this film rather than the substrate, and can be pulled off. These are the scenarios in which a primer is required.
2. If the single-ply membrane is too far gone, you will start to see the scrum, or inside of the membrane, show through. This scrum will eat away at the silicone and cause failure as well. 

If you avoid these two hazards of single-ply, restoring with silicone is as close to a sure thing as you can get in construction. The general steps you will need to follow are:

1. Powerwash entire roof surface,
2. Apply P-151 Single-Ply Primer if adhesion tests require,
3. Replace roof areas greater than 500 square feet containing moisture,
4. Apply FT 500 Butyl Fleece Tape and 25 mils of coating to any flashings that are not watertight,
5. Install silicone at a rate of 20 dry mils for a 5-year warranty, increasing 5 mils for every 5 years of additional warranty desired (up to 35 mils, 20 years).

Installing Silicone Roof Coatings over EPDM

EPDM faces a similar adhesion obstacle as the white single-ply options, in that a film develops on the surface of the substrate. The difference, however, is that the film on EPDM worsens over time, while the film on PVC, TPO and Hypalon membranes goes away over time. This film is reason enough for us to require primer usage in all cases of EPDM restoration. Here’s what you should do:

1. Apply P-120 Rinseable Cleaner,
2. Rinse off after 15 minutes,
3. Power wash entire roof surface,
4. Replace roof areas greater than 500 square feet containing moisture,
5. Apply FT 500 Butyl Fleece Tape and 25 mils of coating to any flashings that are not watertight,
6. Apply FT 500 Butyl Fleece Tape and 25 mils of coating to all membrane seam failures,
7. For 15 and 20-year warranties, apply FT 500 Butyl Fleece Tape and 25 mils of coating to all membrane seams,
8. Install silicone at a rate of 20 dry mils for a 5-year warranty, increasing 5 mils for every 5 years of additional warranty desired (up to 35 mils, 20 years).

Installing Silicone Roof Coatings over Metal Roof Panels

 

Metal roof panels provide another great candidate for silicone roof coating restoration. As long as lap seams are fastened properly and rust is mitigated, there are very few issues that will arise on metal roofs. The process for installing silicone over metal roofing is this:

1. Powerwash entire roof surface,
2. Any rust areas should be cleaned with a wire brush and then receive P-130 Rust Inhibitive Primer,
3. Apply FT 500 Butyl Fleece Tape and 25 mils of coating to any flashings that are not watertight,
4. Replace all fasteners that are loose or backed out,
5. Spot-apply HS 3200 Silicone Roof Coating to all fasteners, this may take up to 2 coats,
6. Powerwash and coat fiberglass skylights with HS 3220 Translucent Skylight Coating,
7. Repair horizontal laps with a gap greater than 1/8″,
8. Install silicone at a rate of 15 dry mils for a 5-year warranty, increasing 5 mils for every 5 years of additional warranty desired (up to 30 mils, 20 years).

Installing Silicone Roof Coatings over Modified Bitumen and Smooth Surface BUR

Silicone over mod-bit and smooth BUR are both great specs. A primer is typically unnecessary for adhesion and the substrate is often still in great shape at the end of the warranty term. One concern with this spec is that BUR and mod-bit roofs contain materials that can bleed into the silicone, causing it to turn yellow. This has no impact on performance, but is not the intended color of the coating. Another item of note, this spec is not designed for coal tar pitch roofs. These roofs re-emulsify when they reach a certain temperature (by design), which causes the substrate to move like a liquid underneath the silicone, disrupting adhesion.

 

If your roof is aged asphalt or granulated cap sheet, we don’t have a specific installation spec for you, but this spec is a good substitute to use a starting point. Follow these steps to install silicone roof coatings over mod-bit and smooth BUR:

1. Power wash entire roof surface,
2. If aesthetics are a concern, apply P-160 Asphalt Bleed-Block Primer to prevent yellowing,
3. Replace roof areas greater than 500 square feet containing moisture,
4. Apply HS 3200 silicone roof coating, polyester fabric, and another layer of silicone roof coating to any flashings that are not watertight,
5. Apply HS 3200 silicone roof coating, polyester fabric, and another layer of silicone roof coating to all seam failures,
6. Apply 20 mils of HS 3200 to all membrane seams,
7. Install silicone at a rate of 25 dry mils for a 5-year warranty, increasing 5 mils for every 5 years of additional warranty desired (up to 40 mils, 20 years).

Installing Silicone Roof Coatings over Gravel Built-Up Roofs

1. It’s very important that you get all loose rock off the roof before applying any material, primer or coating. These loose rocks can break off later and cause discoloring. 
2. This spec is not for coal tar pitch roofs, similar to the smooth BUR spec.
3. The primer is required only for aesthetics, similar to the smooth BUR spec.
4. It is not recommended to use a roller with this spec, only spray application. Rollers can pull up rocks, causing bleeding issues.

1. Remove all loose gravel by broom or vacuum,
2. Power wash entire roof surface,
3. Spray-apply P-160 Asphalt Bleed-Block Primer,
4. Replace roof areas greater than 500 square feet containing moisture,
5. Apply HS 3200 silicone roof coating, polyester fabric, and another layer of silicone roof coating to any flashings that are not watertight,
6. Spray-apply SL 800 Surface Leveling Coating at a rate of 3-6 gallons per square, depending on surface texture,
7. After 1-2 days, install HS 3200 Silicone Roof Coating at a rate of 30 dry mils for a 5-year warranty, and 40 dry mils for a 10-year warranty.

Installing Silicone Roof Coatings over Structural Concrete Roof Deck