Direct Answer
Before applying either silicone or acrylic roof coating, the existing commercial roof must be evaluated, cleaned, dried, repaired, and tested for coating adhesion. The preparation is similar for both systems, but the exact primer, seam treatment, and substrate requirements depend on the existing roof and the manufacturer’s approved assembly. GAF specifically requires the roof to have positive drainage, be clean and dry, and have damaged membrane, flashings, and penetrations repaired before coating.
Who This Applies To
This guidance applies to commercial property owners, facility managers, property managers, contractors, and building owners considering silicone or acrylic roof restoration in Florida.
Not for: Roofs with major structural deterioration, extensive wet insulation, severe membrane failure, or other conditions where a coating would simply cover an underlying roof problem.
1. Inspect and Qualify the Existing Roof
The first step is determining whether the existing roof is suitable for restoration. A contractor should inspect the membrane, insulation, deck where accessible, seams, flashings, penetrations, drains, curbs, edges, and previous coatings.
For some restoration systems, a moisture scan is also appropriate to identify wet insulation or trapped moisture. GAF’s restoration procedures for asphaltic roofs specifically call for identifying wet areas before coating.
A coating should not be used to hide widespread moisture or significant roof deterioration.
2. Clean the Roof Thoroughly
The roof needs to be free of dust, dirt, oils, leaves, debris, and other contaminants that could interfere with adhesion. Pressure washing with an appropriate roof cleaner is commonly used, followed by thorough rinsing.
GAF recommends cleaning the roof with its cleaning concentrate and power washing for applicable restoration systems. The roof must then be allowed to dry completely.
This step is particularly important in Florida because roofs can accumulate biological growth, airborne pollutants, dirt, and other contaminants between maintenance cycles.
3. Make Necessary Roof Repairs
Before coating, damaged areas should be repaired rather than simply covered. Typical preparation can include:
- Repairing damaged membrane areas
- Replacing wet insulation where required
- Replacing loose or missing fasteners
- Repairing damaged metal
- Repairing flashings
- Repairing or sealing penetrations
- Addressing damaged seams
- Correcting drainage problems where practical
- Repairing deteriorated curbs and other roof details
For metal roofs, GAF specifically recommends securing or replacing loose or missing fasteners and repairing sheet-metal deficiencies before coating.
4. Perform an Adhesion Test
An adhesion test should be performed before applying the full coating system. This determines whether the selected coating will properly bond to the existing substrate.
If adhesion is inadequate, a compatible primer may be required. GAF recommends test patches before coating and notes that primer may be recommended or required depending on the substrate.
5. Apply the Correct Primer When Required
Primer requirements are not identical for every roof. They depend on the existing membrane, surface condition, coating system, and manufacturer requirements.
| Existing Roof Condition | Possible Preparation |
|---|---|
| TPO | Cleaning, adhesion testing, and compatible primer when specified |
| EPDM | Cleaning, preparation, adhesion testing, and compatible primer when required |
| Metal | Cleaning, rust treatment where required, fastener repair, and compatible primer |
| Asphaltic roof | Cleaning, moisture evaluation, repairs, and often a bleed-blocking/base primer |
| Concrete | Cleaning, curing verification, adhesion testing, and primer where specified |
| Previously coated roof | Cleaning, adhesion testing, compatibility evaluation, and primer where required |
For example, GAF’s silicone restoration system over asphaltic roofs uses a primer to help prevent asphaltic bleed-through, while Henry offers primers specifically designed to promote silicone adhesion to several roof substrates.
6. Detail Seams, Flashings, Drains, and Penetrations
These areas require particular attention because they are common locations for movement and water intrusion.
Depending on the system, contractors may use compatible mastic, flashing material, reinforcement fabric, or other approved detailing materials around:
- Roof seams
- Penetrations
- HVAC curbs
- Drains and scuppers
- Pipe penetrations
- Roof edges
- Rake edges
- Fasteners
For example, GAF’s silicone restoration procedures call for silicone mastic and fabric at specified seams, curbs, penetrations, and drains. Its acrylic restoration system uses compatible acrylic flashing and reinforcement fabric for similar details.
7. Make Sure the Roof Is Completely Dry
This is especially important for silicone. Silicone is a moisture-cure coating, but that does not mean it should be applied over a wet roof substrate. GAF states that the roof must be dry before silicone application because moisture at the substrate can interfere with adhesion.
Acrylic systems also require a clean and dry substrate, and weather conditions must be suitable for the specific product.
8. Verify Weather and Application Conditions
Before application, the contractor should verify the manufacturer’s requirements for temperature, humidity, dew point, rain, substrate moisture, and curing conditions.
This matters in Florida because afternoon thunderstorms and high humidity can affect the application window. The roof should not be coated immediately before expected rain unless the selected product specifically permits those conditions.
Silicone vs. Acrylic Preparation
| Preparation Step | Silicone | Acrylic |
|---|---|---|
| Roof inspection | Required | Required |
| Clean surface | Required | Required |
| Completely dry substrate | Required | Required |
| Repair damaged areas | Required | Required |
| Adhesion testing | Recommended/required by system | Recommended/required by system |
| Primer | Substrate-dependent | Substrate-dependent |
| Seam/detail treatment | Required where specified | Required where specified |
| Moisture evaluation | Important | Important |
Bottom Line
The success of either coating depends heavily on preparation. The basic sequence is: inspect the roof, identify moisture and deterioration, clean it, make repairs, test adhesion, apply the correct primer when required, detail seams and penetrations, allow the substrate to dry, and then apply the coating at the manufacturer’s specified thickness.
Silicone and acrylic should not be selected simply because one coating is easier to apply. The existing roof assembly, moisture condition, drainage, substrate compatibility, expected exposure, warranty requirements, and Florida project requirements should all be considered before choosing the system.
Related Questions
- Can I apply silicone over an existing acrylic coating?
- What is the energy efficiency benefit of these coatings?
- How often do acrylic coatings need reapplication in Florida?
- Does ponding water void the warranty of an acrylic coating?
Sources
- GAF — When and How to Install Silicone Commercial Roof Coatings
- GAF — Silicone Roof Coating System over Asphaltic
- GAF — Silicone Roof Coating System over Metal
- GAF — Acrylic Roof Coating System over Asphaltic
- GAF — HydroStop Acrylic Roof Coating System
Last reviewed: October 2026
Related Resources
Proper preparation should be documented as part of the roof restoration record, including inspection findings, moisture testing, repairs, adhesion testing, primer selection, and coating application.
Need Commercial Roofing Help?
Have your existing commercial roof evaluated before selecting a silicone or acrylic restoration system.
Disclaimer: Preparation requirements vary by substrate, existing roof assembly, coating manufacturer, warranty requirements, and site conditions. The manufacturer’s current technical documentation and approved assembly should control the installation.
Commercial Roof Inspection Services
