Liquid Roof Coatings: Silicone, Acrylic, Polyurethane and Polyurea

A liquid roof coating is a fluid-applied, fully adhered elastomeric film of acrylic, silicone, polyurethane or asphalt that waterproofs and reflects heat on an existing low-slope roof, and US building codes list 7 ASTM material standards for it.

Acrylic coatings follow ASTM D6083/D6083M-24, silicone coatings ASTM D6694/D6694M-25, moisture-cured polyurethane ASTM D6947/D6947M-16(2023), and asphalt coatings four further standards listed in IBC 2021 Section 1509. In the South Coast air district, SCAQMD Rule 1113 (amended 2016-02-05) limits roof coatings to 50 g/L (0.42 lb/gal) of VOC. Among the construction chemicals used for waterproofing, roof coatings are the class that restores a roof instead of replacing it, one branch of construction chemicals.

The build is specified as dry film: 1 L/m² applies 1.0 mm of wet film and 1 US gal per 100 ft² applies 16.04 mils wet, and one silicone data sheet sets approximately 22 mils (0.56 mm) dry per coat at 1.5 US gal per 100 ft² (0.61 L/m²). Cure times hold only at their temperature, recover rules in IBC 2021 Section 1512.2.1.1 decide whether a roof can be coated at all, and the EU assesses kits under EAD 030350-00-0402 instead of a harmonised standard.

Standards, codes and regulations are checked against their issuing bodies, product values against the named data sheet and prices against the dated source named in the sentence; see our methodology and fact-checking.

The table below sums up the class in seven attributes.

What Is a Liquid Roof Coating?#

A roof coating is, under the US federal definition in 40 CFR 59.401, a coating formulated for exterior roofs to keep water out of the substrate or to reflect heat and ultraviolet radiation. The same definition excludes thermoplastic rubber coatings. Roof coatings are supplied as one-component liquids and are sprayed, rolled, brushed or squeegeed onto an existing roof, a metal roof or sprayed polyurethane foam (SPF).

This reference covers coatings specified for commercial low-slope roofs. Trade usage gives the class four further names: elastomeric roof coating, cool roof coating, roof restoration coating and SPF roof coating. Within waterproofing membranes and systems, the coating is the layer that renews a roof left in place, one of the 13 types compared under waterproofing membranes and systems.

Acrylic, silicone, polyurethane and asphalt: the four roof coating chemistries#

Four binder families make up liquid roof coatings: acrylic latex, silicone, polyurethane and asphalt. Polyurea is sprayed on roofs as well but forms its own product class. The five binder entries are listed below.

• Acrylic latex: a water-dispersed acrylic elastomer that forms its film as the water evaporates, made to ASTM D6083/D6083M-24 in Type I or Type II; the binder chemistry is described under acrylic polymers.
• Silicone: a principal polymer above 95 % silicone in the ASTM D6694/D6694M-25 scope, which covers solvent-dispersed coatings over SPF roofing, while 100 % silicone solvent-free grades are also sold; see silanes, siloxanes and silicones.
• Polyurethane: one-component moisture-cured coatings to ASTM D6947/D6947M-16(2023) and aliphatic grades such as Sikalastic-641 Lo-VOC; the prepolymer chemistry is described under polyurethane resins and prepolymers.
• Asphalt: emulsion and cutback coatings that incorporate bitumens, the 40 CFR 59.401 definition of a bituminous coating; the binder is described under bitumen and polymer-modified bitumen, and foundation use belongs to bituminous dampproofing coatings.
• Polyurea (separate class): an isocyanate reacted with an aromatic or aliphatic amine (pure polyurea) or with an amine-polyol blend (hybrid), sprayed as a membrane and described under polyurea waterproofing membranes.

Roof coating, roof sealant or roof paint: which product is meant?#

A roof coating covers the whole roof surface, while a roof sealant closes seams, flashings and penetrations, and SCAQMD regulates the two under different rules. Rule 1113 sets 50 g/L (0.42 lb/gal) for roof coatings, and Rule 1168, amended 2022-11-04, sets 300 g/L (2.50 lb/gal) for all other roof sealants. Metal roofs show the split: seams and fasteners take a sealant, and the metal roof surface takes a coating. Driveway and parking-lot sealers are not roof coatings.

Regional names add two more meanings, set out in the table below. "Roof waterproofing paint" is the name used in India for an acrylic roof coating, while "liquid roofing" in the UK names liquid-applied membranes rather than coatings. Seam, flashing and joint products belong to the construction sealants class, compared under construction sealants.

The table below sorts five product names by region or rule.

How Does a Roof Coating Cure and Reflect Heat?#

Acrylic roof coatings dry by coalescence as their water evaporates, while silicone and moisture-cured polyurethane coatings cure by reacting with moisture in the air. Each chemistry forms one monolithic, fully adhered film without seams over the existing roof, the metal panels or the foam.

Curing speed follows the mechanism. A water-dispersed acrylic needs drying weather, while a silicone needs air moisture, so low humidity lengthens silicone dry time, as the GacoFlex S20 application instructions state.

Heat reflection comes from the color of the film. White grades reflect solar heat, and that property gives the class its second name, cool roof coating. Reflection is reported through a rating program rather than a material standard: the Cool Roof Rating Council (CRRC) lists solar reflectance and thermal emittance, measured initially and after 3 years of aging.

Where Are Liquid Roof Coatings Used?#

Liquid roof coatings are used on five low-slope substrates: single-ply membranes, metal roofs, smooth and granulated modified bitumen and built-up roofs, sprayed polyurethane foam, and concrete roofs. The five substrates are listed below with the condition that matters for the coating.

• Single-ply membranes: existing sheet roofs restored in place; the choice of system for a whole flat roof is compared under roof waterproofing for flat roofs.
• Metal roofs: the coating goes on the panel surface, and a sealant closes the seams and fasteners.
• Modified bitumen and built-up roofs, smooth or granulated: asphaltic substrates that take a bleed-blocking sealer before a light-colored coating, and granulated surfaces take a higher rate per area.
• Sprayed polyurethane foam: the coating is the protective layer of the foam, applied no less than 2 h and no more than 72 h after the foam (IBC 2021 Section 1507.13).
• Concrete roofs: roof decks of concrete, cleaned and dried like every other substrate before priming.

Every substrate sits under the same slope rule. IBC 2021 and FBC 2023 set a minimum design slope of 2 % (1/4:12) for membrane and liquid-applied roofs and 1 % (1/8:12) for coal-tar built-up roofs. Asphalt emulsion coatings to ASTM D1227 need more: slopes of at least 4 % (1/2 in/ft).

Which Properties Define a Roof Coating's Performance?#

Six film properties decide how a roof coating performs: elongation and tensile strength, adhesion, tear resistance, low-temperature flexibility, water-vapor permeance and the retention of these after accelerated weathering. ASTM D6083/D6083M-24 tests 11 properties for acrylic coatings, from viscosity and solids to water swelling, fungi resistance and low-temperature flexibility. ASTM D6694/D6694M-25 sets liquid and film properties for silicone over SPF, including elongation, tensile strength, permeance, weathering, adhesion, tear and low-temperature flexibility.

The table below names the test method behind each film property.

The code adds a weathering floor of its own. IBC 2021 Section 1504.7 requires roof coverings installed on low-slope roofs to demonstrate physical integrity based on 2,000 h of exposure to accelerated weathering conducted to ASTM G152, G154 or G155.

Standard requirement or product value: how to read roof coating data#

A standard requirement is the minimum every compliant product reaches in the named test, while a data-sheet value is what one product reached or what one maker specifies. The difference decides how a roof build is written. A dry film of approximately 22 mils (0.56 mm) per coat is the GacoFlex S20 instruction at 1.5 US gal per 100 ft² (0.61 L/m²) on smooth roofs, not a D6694 requirement. ASTM D6694/D6694M-25 sets material properties, not a roof build. Numeric limits of D6083 and D6694 are read in the standards themselves, bought from ASTM, never from a data-sheet summary.

Which Standards Govern Roof Coatings: ASTM D6083, D6694, D6947 and EU Kits?#

IBC 2021 Section 1509 and FBC 2023 Table 1509.2 list 7 roof coating material standards: ASTM D6083 for acrylic, D6694 for silicone, D6947 for moisture-cured polyurethane and four asphalt standards. The EU has no harmonised standard for these products and assesses liquid-applied roof waterproofing kits under EAD 030350-00-0402. No class system runs across the four chemistries: each standard covers one binder, so a data sheet claims the standard of its own chemistry.

The table below sets each chemistry beside its US standard, scope, code listing and EU basis.

US material standards listed by IBC 2021 and FBC 2023#

ASTM D6083/D6083M-24 covers water-dispersed acrylic latex elastomeric roof coatings in Type I and Type II and tests 11 liquid and film properties, from viscosity and solids to tear and low-temperature flexibility. ASTM D6694/D6694M-25 covers liquid-applied, solvent-dispersed silicone elastomeric coatings over sprayed polyurethane foam roofing whose principal polymer exceeds 95 % silicone. ASTM D6947/D6947M-16(2023) covers one-component moisture-cured polyurethane coatings for the same SPF roofs. Both acrylic types appear in the market: the Polyglass 2026 acrylic brochure lists its products against D6083 Type I and Type II.

Four asphalt standards complete the code list. ASTM D1227, as listed in IBC 2021 Section 1509, covers emulsified asphalt roof coatings for slopes of at least 4 % (1/2 in/ft). ASTM D4479/D4479M-07(2024) covers asbestos-free asphalt roof coatings, Type I nonfibered and Type II fibered, of brushing or spraying consistency, while D2823 (asphalt) and D2824 (aluminum-pigmented asphalt) are named by number in the same section. On foam roofs the code also sets timing: IBC 2021 Section 1507.13 and FBC 2023 Section 1507.14.3 require the protective coating no less than 2 h and no more than 72 h after the foam.

European assessment: EAD 030350 and EAD 030019 kits#

No harmonised EN covers liquid-applied roof waterproofing kits, so EU products carry a European Technical Assessment against EAD 030350-00-0402, and silicone (polysiloxane) kits are assessed under EAD 030019-00-0402. EAD 030350-00-0402 dates from August 2018, was cited in the Official Journal in 2020 and succeeds ETAG 005:2000. It classifies kits by assumed working life (W1 5 years, W2 10 years, W3 25 years, with 10 years as the default assumption) and by roof slope (S1 below 5 %, S2 5 to 10 %, S3 10 to 30 %, S4 above 30 %). Temperature classes run from TL1 +5 °C (41 °F) to TL4 -30 °C (-22 °F) at the low end and from TH1 30 °C (86 °F) to TH4 90 °C (194 °F) at the high end, and user load runs from P1 to P4. The EAD excludes vehicle-accessible roofs, bridges and uses covered by EN 1504-2.

Cool roof ratings: CRRC and California Title 24#

A cool roof rating reports a coating's solar reflectance and thermal emittance, both initial and after 3 years of aging, and California Title 24 Section 110.8(i)4 refers to Cool Roof Rating Council (CRRC) listings. The rating is a product listing, not a class value, so a specifier reads the CRRC listing of the exact product on the order. The aged value matters because dirt pickup and loss of reflectance is one of the recorded failure modes of roof coatings.

How do you check a D6083 or D6694 claim on a data sheet?#

Five checks confirm a roof coating's standard claim on its data sheet.

1. Name the standard with its edition (ASTM D6083/D6083M-24, D6694/D6694M-25 or D6947/D6947M-16(2023)), not a bare number.
2. Find the D6083 type, Type I or Type II, on an acrylic claim.
3. Match the substrate scope: D6694 and D6947 are written for SPF roofing.
4. Look up the CRRC listing with its initial and 3-year aged values.
5. Read the VOC content in g/L against the local rule, 50 g/L (0.42 lb/gal) for roof coatings under SCAQMD Rule 1113.

For an EU product the same review reads the ETA number and the EAD 030350-00-0402 categories for working life, slope, temperature and user load.

How Do You Choose a Roof Coating?#

Choose a roof coating by substrate and water exposure first and by warranty build and VOC limit second: acrylic where the roof drains, silicone where the maker's warranty covers ponding water. Asphalt emulsion coatings to ASTM D1227 suit only slopes of at least 4 % (1/2 in/ft). SPF roofs take a D6083, D6694 or D6947 coating within the 2 to 72 h code window.

The table below matches six roof situations to a coating and its basis.

The silicone vs acrylic roof coatings question turns on ponding water and on recoating. Ponding water softens acrylic coatings, while silicone ponding performance is set by each product's warranty rather than by a standard value. Silicone also limits what goes over it later, because coating-over-coating delamination is a recorded failure mode. Recoat, cost and standards for the pair are compared under silicone vs acrylic roof coatings.

When is a liquid roof coating the wrong product?#

Five situations call for another product class or a new roof instead of a coating. The five are listed below.

• Wet or deteriorated roof, or two existing coverings: IBC 2021 Section 1512.2.1.1 does not permit a recover over a water-soaked or deteriorated roof or over two or more existing roof coverings.
• Wet insulation: an infrared or core survey that finds wet insulation sends the area to repair before any restoration coating goes down.
• Vehicle or pedestrian traffic decks: a liquid membrane with an integral wearing surface to ASTM C957/C957M-25 belongs there, under traffic coatings for parking decks.
• Buried or protected membranes: ASTM C836/C836M-18(2022) membranes with a separate wearing course, or hot-applied rubberized asphalt, under liquid-applied waterproofing membranes.
• Full membrane replacement: a new sheet roof, chosen from sheet waterproofing membranes.

How Is a Roof Coating Applied? Preparation, Thickness, Coverage and Cure#

A roof coating application is specified by four items: a clean, dry, sound roof, the primer or bleed blocker the substrate needs, the wet film per coat that delivers the warranty dry film, and the cure window. The three subsections below give the values that the code and the named data sheets set.

Surface preparation, bleed blockers and primers#

Preparation cleans the roof by power washing, treats biological growth, repairs seams and flaws and lets the roof dry completely before any primer goes down. Cleaning comes first because poor adhesion on dirty or wet roofs is a recorded failure mode of the class. Before a restoration is specified, an infrared or core survey checks the insulation for water, since wet insulation is a repair item, not a coating substrate.

Primer follows the substrate. Asphaltic substrates, such as smooth or granulated modified bitumen and built-up roofs, take a bleed-blocking sealer so that asphalt does not bleed through a light-colored topcoat, and the rate and dry film of one such sealer appear in the thickness table below. Other substrates take the primer the coating maker names for them, and existing silicone is not primed before a new silicone coat.

Roof coating thickness: wet film, dry film and coverage per gallon#

Roof coating thickness is specified as dry film, and the wet film follows from the coverage rate: 1 L/m² applies 1.0 mm of wet film, and 1 US gal per 100 ft² applies 16.04 mils wet. The dry film equals the wet film multiplied by the coating's volume solids (DFT = WFT × volume solids). At 100 % volume solids, 1 US gal covers 1,604 ft² at 1 mil, which is m²/L = 1,000 × volume solids / DFT in µm in metric terms. A GacoFlex S20 coat at 1.5 US gal per 100 ft² (0.61 L/m²) applies 24 mils (0.61 mm) wet by that identity and approximately 22 mils (0.56 mm) dry on smooth roofs. Gauges check wet and dry film thickness against these numbers on the roof, and the gauge readings are explained under wet and dry film thickness.

The table below converts named data-sheet rates into wet and dry film, with 1 square = 100 ft².

Roof coating temperature limits and cure times#

One silicone roof coating, GacoFlex S20, is recoatable and walkable after at least 4 h at 13 °C (55 °F) or warmer, with a recoat window of 4 to 48 h and light foot traffic after 24 to 48 h. Those times belong to one product at one temperature and are not class values, and acrylic and polyurethane times come from their own data sheets. Low humidity lengthens silicone cure, because the film cures with air moisture.

The table below keys each cure and window value to its temperature and source, including the code timing for foam roofs.

How Are Roof Coatings Inspected, and Why Do They Fail?#

Roof coatings are accepted on adhesion and film build: adhesion test patches show whether the coating bonds before the whole roof is coated, and wet and dry mil readings show whether the warranty build was reached. Peel adhesion test patches go on the cleaned and primed roof at the start, because poor adhesion and coating-over-coating delamination are two of the five failure modes recorded for the class. Wet mil gauges check each coat as it goes down, and dry mil readings on the cured film confirm the result.

Coverage reconciliation compares the gallons applied with the area and the warranty rate. Worked example: the inputs are a roof area of 929 m² (10,000 ft²) and a warranty rate of 0.61 L/m² (1.5 US gal per 100 ft²). The build needs 568 L (150 US gal) of coating, so delivery records showing less coating on that area mean the warranty build was not reached.

The table below lists six failures, their causes and the check that finds each.

What Health, Safety and VOC Rules Apply to Roof Coatings?#

Roof coating hazards depend on the chemistry: moisture-cured polyurethanes contain diisocyanates regulated by REACH Annex XVII entry 74, and solvent-borne silicones and polyurethanes carry flammable solvents. The hazard statements of any product come from its own safety data sheet (SDS), not from the class. Acrylic and styrene-acrylic dispersions have no CLP Annex VI entry as a polymer class; see the product SDS.

Moisture-cured polyurethane coatings and diisocyanates#

Products with 0.1 % by weight or more of diisocyanates, individually and in combination, may be used industrially or professionally in the EU only after training, required since 2023-08-24 and renewed at least every five years. These diisocyanates rules sit in REACH Annex XVII entry 74, added by Regulation (EU) 2020/1149, and since 2022-02-24 the supplier label carries the statement "As from 24 August 2023 adequate training is required before industrial or professional use." Polyurethane resins and prepolymers have no Annex VI entry as a class. Where the SDS names 4,4'-methylenediphenyl diisocyanate (4,4'-MDI, CAS 101-68-8), its harmonised CLP Annex VI entry, index 615-005-00-9, includes Resp. Sens. 1 H334 and Skin Sens. 1 H317. Training levels and exposure limits are set out under diisocyanates rules.

Solvent-borne silicones, siloxane residues and asphalt coatings#

Silicone polymers are not on the REACH Candidate List themselves, but the cyclic siloxane residues D4, D5 and D6 are listed there since 2018-06-27 and fall under Annex XVII entry 70. Under entry 70 as replaced by Regulation (EU) 2024/1328, D4, D5 and D6 may not be placed on the market at 0.1 % by weight or more each after 2026-06-06, with derogations. Polydimethylsiloxane has no CLP Annex VI entry, while octamethylcyclotetrasiloxane (D4) carries Annex VI index 014-018-00-1 with Repr. 2 H361f and Aquatic Chronic 1 H410; for a coating, see the product SDS.

Bitumen (CAS 8052-42-4) has no Annex VI entry; ECHA C&L notified: not classified (97.8 %); see the product SDS. Asphalt emulsion and cutback roof coatings therefore take their classification from their own SDS, and a cutback adds the hazards of its solvent as stated there.

VOC limits for roof coatings and roof sealants#

SCAQMD Rule 1113, as amended 2016-02-05, limits roof coatings to 50 g/L (0.42 lb/gal), aluminum roof coatings to 100 g/L (0.83 lb/gal) and bituminous roof primers to 350 g/L (2.92 lb/gal). These VOC limits for construction chemicals attach to the product category, so a coating, a primer and a seam sealant on one roof meet three different numbers. The categories of other products and states are listed under VOC limits for construction chemicals.

The table below lists the roof categories by jurisdiction and date.

Outside the South Coast, the federal EPA AIM rule (40 CFR 59 subpart D, Table 1) limits roof coatings to 250 g/L (2.09 lb/gal) and bituminous coatings and mastics to 500 g/L (4.17 lb/gal) for coatings made on or after 1999-09-13. Roof sealants fall under SCAQMD Rule 1168 (amended 2022-11-04): all other roof sealants 300 g/L (2.50 lb/gal), and single-ply roof membrane sealant and cut-edge sealant 250 g/L (2.09 lb/gal) since 2023-01-01, down from 450 g/L. There is no federal VOC content limit for adhesives or sealants.

What Does a Liquid Roof Coating Cost?#

Commercial installed roof coating costs USD 16.15 to 43.06 per m² (USD 1.50 to 4.00 per ft²) for acrylic and USD 21.53 to 53.82 per m² (USD 2.00 to 5.00 per ft²) for silicone, Southern California, Method Roofing, 2026. A second contractor page prices an installed silicone roof coating system at USD 37.67 to 75.35 per m² (USD 3.50 to 7.00 per ft²), US, West Roofing Systems, 2026-07. Both are installed prices from single contractor pages, not quotes; a quote follows from roof area, the condition survey, the warranty build and the local VOC rule.

The table below lists the two dated ranges with their basis.

What Are the Alternatives to Liquid Roof Coatings?#

Six product classes compete with liquid roof coatings, and each wins where the roof needs a new waterproofing layer rather than a restored surface, or where traffic or burial rules a coating out. Liquid-applied membranes of polyurethane, PMMA or hybrids form a new bonded membrane, including buried ones to ASTM C836/C836M-18(2022). Sheet membranes and modified bitumen bring factory-set thickness, and polyurea sprays a seamless membrane, about 2 mm thick for Sikalastic-851. Hot rubberized asphalt serves buried and protected decks, and traffic coatings carry wheels and feet on an integral wearing surface.

The table below sets each alternative beside its chemistry, the case it wins and its standard.

Roof Coating Grades, Packaging and Sourcing#

Roof coatings are sold as one-component liquids in pails, drums and totes, and buyers compare them on the ASTM standard and type, the CRRC listing, the VOC content and the warranty build. Construction chemicals manufacturers and suppliers publish each of those values on the data sheet, the SDS and the warranty build sheet. How to compare those documents across makers is set out under construction chemicals manufacturers and suppliers.

The five comparison points for a roof coating purchase are listed below.

• Standard and type: ASTM D6083/D6083M-24 Type I or II, D6694/D6694M-25, D6947/D6947M-16(2023), or an ETA to EAD 030350-00-0402.
• Cool roof listing: the CRRC product listing with initial and 3-year aged values.
• VOC content: g/L (lb/gal) against the local limit, 50 g/L (0.42 lb/gal) in the South Coast air district or 250 g/L (2.09 lb/gal) under EPA AIM.
• Warranty build: the rate per 100 ft² or per m² and the dry film the maker ties to each warranty term.
• Pack and documents: pail, drum or tote, with the data sheet, the SDS and the warranty build sheet.

Warranted commercial systems need a roofing contractor accepted by the coating maker, so the product and the applicator are chosen together.

Where Does a Roof Coating Fit in a Low-Slope Roof System?#

A roof coating is the restoration layer of a low-slope roof system: it renews the weathering surface of a sound existing roof, while wet insulation, failed seams or a second existing covering call for repair or replacement first. Below the coating sit the existing membrane, the insulation and the deck, and the coating protects that membrane from sun and water.

On sprayed polyurethane foam the coating is part of the roof from the start, applied 2 to 72 h after the foam under IBC 2021 Section 1507.13. In roof waterproofing for flat roofs, a coating is one of three layer forms beside sheets and liquid membranes. How the three compare on a whole roof is set out under roof waterproofing for flat roofs.

Liquid roof coating FAQs#

Six questions about liquid roof coatings are answered below.

Will a roof coating stop leaks?#

A roof coating stops leaks only after the leak source is repaired. Preparation repairs seams and flaws first, and IBC 2021 Section 1512.2.1.1 does not permit a recover over a water-soaked or deteriorated roof, so wet areas found in the survey are replaced before the coating goes on.

Can you coat over an existing silicone roof coating?#

Silicone goes over existing silicone without primer in the GacoFlex S20 application instructions. Other coatings over silicone risk delamination, a recorded failure mode of the class, so adhesion test patches decide before the whole roof is coated.

How much does 5 gallons of elastomeric roof coating cover?#

At the Polyglass 10-year acrylic build of 2.5 to 3.0 US gal per 100 ft² total wet, 5 US gal (18.9 L) covers 15.5 to 18.6 m² (167 to 200 ft²). Builds differ by product and warranty term, so the same pail covers less area at a 15-year or 20-year build.

How long does a 100 % silicone roof coating last?#

No roof coating standard sets a service life. Makers tie the warranted term to the applied rate, as the warranty builds in the thickness table show, and EAD 030350-00-0402 assesses EU kits against an assumed working life of 5, 10 or 25 years (W1 to W3).

Is an elastomeric roof coating the same as an elastomeric wall coating?#

No: an elastomeric roof coating is formulated for exterior roofs under the 40 CFR 59.401 definition. Elastomeric wall coatings for concrete and masonry form a separate product class, described under elastomeric wall coatings.

Are roof coatings used on shingle or wood roofs?#

Residential steep-slope shingle and wood roofs are outside this reference, which covers coatings specified for commercial low-slope roofs.