Elastomeric Roof Coating
Types, application, recoat compatibility, and cost for commercial and residential roofs
Last updated: March 28, 2026
Contents
Overview
Elastomeric roof coatings are liquid-applied waterproof membranes that stretch and recover with your roof as temperatures change. They use polymer binders (acrylic, silicone, polyurethane, or synthetic rubber) to form a seamless, flexible film that bonds directly to the existing roof surface. Unlike tear-off and replacement, coatings restore and extend the life of a roof that still has structural integrity.
Building owners, facility managers, and roofing contractors use elastomeric coatings on commercial flat roofs, metal roofs, built-up roofs, and spray foam systems. White (cool roof) coatings reflect sunlight, cut cooling costs, and reduce urban heat island effects. A properly applied coating system can add 10 to 20 years to an existing roof at a fraction of full replacement cost.
Key point: A coating is not a patch for a failing roof. The substrate must be structurally sound, properly draining, and free of moisture damage before coating. All cracks, open seams, and flashings need repair first.
Types of Elastomeric Coatings
Four coating chemistries cover the vast majority of commercial and residential applications. Each has trade-offs around ponding water tolerance, recoatability, and cost.
Acrylic
Water-based acrylic latex coatings are the most common and budget-friendly option. They offer high reflectivity and UV protection, making them a solid choice for warehouses, schools, and light commercial buildings with proper roof slope and drainage. Cleanup is easy (soap and water), and recoating with acrylic down the road is straightforward. The main limitation is ponding water. Standing water can soften acrylic film over time, so these coatings work best on roofs that drain within 48 hours after rain.
Silicone
Silicone coatings are the go-to for roofs with ponding water problems. The polysiloxane chemistry is naturally hydrophobic and UV stable, so silicone handles standing water and sun exposure better than any other coating type. High-solids silicone can often be applied in a single pass. The downsides: silicone attracts dirt (reducing reflectivity over time), the cured surface can be slippery when wet, and it costs more per square foot. Future recoats require abrasion or a tie-coat primer because most coatings will not adhere to cured silicone without surface preparation.
Polyurethane
Polyurethane coatings are the toughest option for roofs with regular foot traffic or rooftop equipment access. A typical system uses an aromatic base coat for adhesion and impact resistance, topped with an aliphatic UV-stable topcoat to maintain reflectivity. Polyurethane handles ponding better than acrylic but not as well as silicone. The trade-off is complexity: these are moisture-cure systems with recoat windows you need to hit, and they cost more to install.
SEBS Rubber
SEBS (Styrene-Ethylbutylene-Styrene) is a solvent-based synthetic rubber coating often specified for metal roofs. It cures fast, bridges cracks well, and resists acid and alkali exposure. The drawback is higher VOC content, which may not meet regulations in all jurisdictions. Reflectivity can fade without a topcoat. SEBS is common on industrial sheds, metal buildings, and facilities where chemical splash is a concern.
Coating Comparison
| Type | Temperature Range | Ponding Water | Recoatability | Typical Cost/sqft | Best For |
|---|---|---|---|---|---|
| Acrylic | 50-90F application | Poor, softens under standing water | Excellent, easy same-chemistry recoat | $0.75-$1.25 | Well-drained roofs, budget projects |
| Silicone | 35-120F application | Excellent, fully resistant | Difficult, needs abrasion or tie-coat | $1.50-$2.00 | Ponding-prone flat roofs |
| Polyurethane | 40-100F application | Good, better than acrylic | Moderate, recoat windows apply | $1.25-$2.00 | High-traffic roofs, equipment areas |
| SEBS Rubber | 25-110F application | Fair to good | Good with same chemistry | $1.00-$1.75 | Metal roofs, chemical exposure |
Recoat Compatibility
Recoat compatibility is the single biggest source of elastomeric coating failures. Not every coating can go over every existing coating. Applying an incompatible coating leads to delamination, peeling, and a failed system that has to be stripped and redone. Before recoating, always identify the existing coating chemistry and check the matrix below.
Warning: Acrylic over silicone is the most common mistake. Acrylic will not adhere to cured silicone, period. The coating will peel off in sheets. If you have an existing silicone roof, your recoat options are silicone (with primer/abrasion) or a full removal.
Compatibility Matrix
| New Coating (over) | Existing Acrylic | Existing Silicone | Existing Polyurethane | Existing SEBS |
|---|---|---|---|---|
| Acrylic | Yes | No | Yes, with primer | Yes, with primer |
| Silicone | Yes, with primer | Yes, with abrasion or tie-coat | Yes, with primer | Yes, with primer |
| Polyurethane | Yes, with primer | No | Yes, check recoat window | Yes, with primer |
| SEBS | Yes, with primer | No | Yes, with primer | Yes |
"With primer" means the existing surface must be cleaned, any loose material removed, and a manufacturer-recommended primer applied before the new coating. "With abrasion" means the existing surface needs to be mechanically scuffed (typically with a sanding disc or power washer at close range) to create a profile for the new coating to grip.
Tip: When you are unsure what coating is already on a roof, do an adhesion test. Apply a small patch of the new coating, let it cure fully, then try to peel it off. If it pulls away cleanly, the coating is incompatible. This 24-hour test can save thousands in rework.
Application
Proper surface preparation and correct mil thickness are the two factors that determine whether a coating system lasts 5 years or 20 years. The coating itself is the easy part.
Surface Preparation
- Pressure wash the entire roof to remove dirt, debris, algae, and loose material
- Repair all cracks, open seams, and failed flashings before coating
- Use fiberglass mesh embedded in coating to reinforce seams and penetrations
- Treat rust on metal roofs with a rust converter or rust-inhibiting primer
- The surface must be completely dry. Trapped moisture causes blistering and delamination
- Apply manufacturer-recommended primer if required for your substrate
Mil Thickness and Warranty
Warranty length is directly tied to dry film thickness (DFT). Most manufacturers follow a similar scale:
| Dry Film Thickness (DFT) | Typical Coverage Rate | Warranty |
|---|---|---|
| 20 mils (0.020 in.) | ~1.5 gal/100 sqft per coat | 10 years |
| 25 mils (0.025 in.) | ~2 gal/100 sqft per coat | 15 years |
| 30 mils (0.030 in.) | ~2.5 gal/100 sqft per coat | 20 years |
Two Coats, Perpendicular
Always apply at least two coats. Roll or spray the second coat perpendicular to the first (if the first coat goes north-south, the second goes east-west). This cross-hatching fills in thin spots and holidays the first coat missed. Allow the first coat to cure fully (typically 24 hours in warm, dry weather, 48 hours in cool or humid conditions) before applying the second coat.
Tip: Apply coatings during late morning to early afternoon to avoid dew and high humidity. Do not apply if rain is expected within 24 hours. For crew PPE and safety equipment, see our roof coating safety kit guide.
For a detailed walkthrough with photos, see our step-by-step application guide.
ASTM Standards
Each coating chemistry has its own ASTM performance specification. These standards define minimum requirements for tensile strength, elongation, reflectance, water absorption, and other properties that determine real-world durability.
| Standard | Coating Type | Key Requirements |
|---|---|---|
| ASTM D6083 | Acrylic | Liquid-applied acrylic coating for roofs, minimum tensile/elongation, reflectance |
| ASTM D6694 | Silicone | Liquid-applied silicone coating for roofs, water immersion, accelerated weathering |
| ASTM D6947 | Polyurethane | Liquid-applied polyurethane coating for roofs, impact and abrasion resistance |
When specifying a coating for a commercial project, reference the appropriate ASTM standard in the bid documents. This ensures the product has been tested to a known performance baseline, not just the manufacturer's marketing claims.
For sealants used at roof penetrations, flashings, and joints, see ASTM C920 (elastomeric joint sealants). For the full ASTM catalog, visit ASTM International.
Cost
Elastomeric coatings cost a fraction of a full roof replacement. Material alone runs $0.75 to $2.00 per square foot depending on the chemistry and mil thickness. Installed by a contractor, expect $2 to $5 per square foot including prep, primer, and two coats. Compare that to $5 to $12 per square foot for a full tear-off and replacement.
| Option | Cost/sqft | Typical Warranty | Downtime |
|---|---|---|---|
| Elastomeric coating (material only) | $0.75-$2.00 | 10-20 years (DFT dependent) | Minimal, building stays open |
| Elastomeric coating (installed) | $2.00-$5.00 | 10-20 years (DFT dependent) | Minimal, building stays open |
| Full roof replacement | $5.00-$12.00 | 20-30 years | Days to weeks, may disrupt operations |
The total project cost depends on roof size, condition of the existing surface (how much prep work is needed), coating chemistry, and target mil thickness. A 10,000 sqft commercial flat roof typically costs $20,000 to $50,000 for a coating system versus $50,000 to $120,000 for full replacement.
Tip: Warranty is directly tied to how thick you apply the coating. If you need a 20-year warranty, you need to hit 30 mils DFT. Trying to save money by applying fewer gallons means a shorter warranty and earlier recoat.
Cool Roof Compliance
White elastomeric coatings qualify as cool roofs under multiple energy codes and programs. A cool roof reflects solar energy and emits absorbed heat, reducing building cooling loads and helping meet energy efficiency requirements.
Title 24 (California)
California's Title 24 energy code sets minimum solar reflectance and thermal emittance values for roof surfaces. Low-slope roofs (2:12 pitch or less) must meet aged solar reflectance of 0.63 and thermal emittance of 0.75 for prescriptive compliance. Most white elastomeric coatings meet or exceed these thresholds. For full Title 24 cool roof requirements, see our cool roof compliance guide.
CRRC Ratings
The Cool Roof Rating Council (CRRC) tests and rates roofing products for solar reflectance and thermal emittance. Look for a CRRC-rated product when specifying coatings for projects that need to document cool roof compliance. CRRC ratings include both initial and aged (3-year weathered) values, which is what code compliance is based on.
Energy Star
The EPA's Energy Star program for roof products requires an initial solar reflectance of 0.65 and a 3-year aged reflectance of 0.50 for low-slope roofs. Energy Star-labeled coatings have been independently tested and verified to meet these minimums. Using an Energy Star coating can support LEED credits and utility rebate programs in some jurisdictions.
Frequently Asked Questions
What is the difference between acrylic and silicone roof coating?
Acrylic is water-based, cheaper, highly reflective, and easy to recoat, but it does not handle ponding water well. Silicone is naturally waterproof, UV stable, and handles standing water without degrading, but it costs more, picks up dirt, and is harder to recoat because most coatings will not stick to cured silicone without abrasion or a tie-coat primer. Choose acrylic for well-drained roofs on a budget. Choose silicone for flat roofs that pond.
Can you apply a roof coating over ponding water areas?
Silicone coatings can handle ponding water without degrading. Acrylic coatings will soften and eventually fail under prolonged standing water. If your roof has areas that pond for more than 48 hours after rain, either fix the drainage, use silicone in those areas, or reinforce with additional mil thickness and fabric. Never coat over actively ponding water during application.
How long does an elastomeric roof coating last?
Warranty life depends on dry film thickness. At 20 mils DFT, most manufacturers warrant 10 years. At 30 mils DFT, you can get a 20-year warranty. Real-world performance also depends on surface prep quality, coating chemistry, and climate. Silicone tends to last the longest in harsh UV environments. Regular inspections and maintenance (washing debris, patching damage) can extend service life beyond the warranty period.
Can I apply elastomeric roof coating myself?
Acrylic coatings are DIY-friendly for small roofs. They apply like thick paint with a roller or airless sprayer and clean up with water. Silicone and polyurethane coatings are more demanding and typically need professional installation to hit the required mil thickness and avoid contamination issues. Regardless of chemistry, surface prep is the critical step. A poorly prepped surface will cause any coating to fail. See our application guide for the full process.
Can I put acrylic coating over existing silicone?
No. Acrylic will not bond to cured silicone and will peel off. This is the most common recoat failure in the industry. If you have an existing silicone coating, your options are to recoat with silicone (after cleaning and abrading the surface) or to completely remove the silicone before applying a different coating type. Always do an adhesion test on a small area before committing to a full recoat.
Do elastomeric roof coatings stop leaks?
Elastomeric coatings can seal small cracks, fissures, and minor gaps in the roof surface. They form a seamless, waterproof membrane that stops water from entering through these small defects. However, coatings cannot fix major structural damage, large holes, or leaks caused by poor drainage. Repair significant damage first, then coat the roof as a waterproof barrier. For leak-prone areas around vents and penetrations, reinforce with fiberglass mesh embedded in the coating.
