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ARMORTHANE PROTECTING YOUR WORLD

PROTECTING YOUR WORLD

ARMORTHANE PROTECTING YOUR WORLD

Silicone Roof
Coating: Pros,
Cons & Cost

What silicone roof coating does well, where it fails, how long it lasts at each mil thickness, and why it limits every recoat after it. Written by a coatings manufacturer that doesn’t sell silicone.
Roof Coating Quotes

Not sure silicone is right for your roof? Get a straight answer from a certified applicator.

Tell us the roof type, the size and whether water stands on it. We'll connect you with an ArmorThane-certified applicator who can look at it and tell you what fits: a sprayed polyurea or foam system, or a coating we don't make.

  • Metal, TPO, EPDM, BUR and spray foam roofs
  • Ponding, foot traffic and hail factored in
  • Film thickness and warranty in writing
  • Contractors: ask about polyurea roofing rigs
Rather talk now? Call (417) 831-5090
Step 1 of 3
34 mils
Dry film behind a 20-year silicone warranty
GacoFlex S42 metal-roof spec, 2026
10–15 yr
Typical silicone coating life
HomeGuide, 2024
$1.50–$4.50
Installed, per square foot
HomeGuide 2024; Angi 2026: $1.50–$2.50
Silicone
The only coating that reliably bonds to cured silicone
Industry recoat guidance

Silicone roof coating is the standard answer for a low-slope roof that holds water. It's also the coating that makes your next roofing decision for you, because once a roof is silicone, the only thing that reliably sticks to it is more silicone.

Quick answer

Silicone is a moisture-cure elastomer that shrugs off ponding water and UV, goes on in cooler, damper weather than acrylic, and typically lasts 10–15 years, or up to 20 when it's applied at a warranted 26–34 dry mils. The trade-offs: it picks up dirt, it's slick when wet, it tears more easily than urethane or polyurea, and at recoat time nothing but silicone bonds to it. Choose it for a sound low-slope roof with drainage problems and light foot traffic. Try the coating selector or the gallons calculator.

A disclosure before anything else: ArmorThane doesn't make silicone roof coating. We make polyurea, polyurethane and spray foam in Springfield, Missouri, and the applicators we supply spray polyurea and foam roofs. That's why we can be blunt here. Silicone is the right call on plenty of roofs, and on some of them our products aren't.

The top results for this search are mostly product listings with little or no data. So this page pulls the numbers out of the data sheets, installation specs and cost surveys and puts them side by side: solids, mils, gallons, warranty tiers, recoat rules and real prices, each with its source. Where the math is ours, we say so.

What's in this guide
  1. 1What silicone roof coating is
  2. 2Pros and cons, with the numbers
  3. 3Silicone vs acrylic vs urethane vs polyurea
  4. 4Which coating fits your roof (selector)
  5. 5How long silicone lasts
  6. 6How much you need (gallons calculator)
  7. 7Recoating silicone (compatibility checker)
  8. 8What it costs (life-cycle calculator)
  9. 9Silicone and ponding water
  10. 10How it's applied
  11. 11Maintenance
  12. 12Where ArmorThane fits, and where it doesn't
  13. 13Silicone roof coating FAQ
The basics

What is silicone roof coating?

Silicone roof coating is a fluid-applied, single-component elastomer whose main polymer is silicone. It cures by pulling moisture out of the air and forms a seamless, rubbery membrane over an existing roof. The ASTM standard for it, D6694, covers coatings whose principal polymer is more than 95% silicone.

It's a restoration product. You put it on a roof that's still sound but aging (metal, single-ply membranes like TPO, EPDM, PVC and Hypalon, smooth built-up roofing, modified bitumen, concrete and spray foam) to seal it, reflect sunlight and push back a tear-off. The IRC recognizes it twice: as liquid-applied roofing (R905.15, which lists ASTM D6694) and as an approved protective coating over spray foam roofing (Table R905.14.3).

Moisture cure has consequences you'll feel on the job. The coating starts curing the moment the pail is opened; Henry warns that a partly used bucket can harden within a day or two. High heat and humidity make it skin faster (Gaco). And cold, dry air slows the cure.

What it isn't for: shingles. Henry says its 887 silicone is "not recommended over shingles of any kind," GacoRoof excludes 3-tab and architectural shingles, and Kool Seal's silicone is "not for use on roof shingles." If you have a shingle roof, repair or replace it.

White fluid-applied roof coating on a low-slope commercial roof with rooftop units and vents
A white fluid-applied membrane on a low-slope commercial roof: the kind of roof silicone is built for.

Solvent-free vs. solvent-borne silicone

Not all silicones carry the same amount of silicone to the roof. The number that matters is volume solids: the share of the liquid that stays on the roof as film after the solvent leaves. It decides how many dry mils you get per gallon, and so how many gallons you buy.

Product (example)TypeSolids by volumeVOCDry mils from 1 gal / 100 sq ft
GacoFlex S42Solvent-free, pro95%<50 g/L (37 g/L in spec)15.2
American WeatherStar High-Solids 412High-solids, pro92% ±2<50 g/L14.8
American WeatherStar Silicone 410Solvent-borne, pro69% ±2<250 g/L11.1
Henry 887 Tropi-CoolRetail, one coatNot in catalog–Rate: 1.5 gal / 100 sq ft
GacoRoofRetail, two coatsNot in FAQVOC-compliant versions soldRate: 1 gal / 50 sq ft finished
Solids and VOC from each maker's data sheet. Dry mils are our calculation: 1 gallon spread over 100 sq ft is 16.04 wet mils, times volume solids.

So a solvent-borne silicone needs about 38% more gallons than a 95%-solids product to reach the same 26 dry mils (2.35 vs 1.71 gallons per 100 sq ft, our math). Compare the price per dry mil, not the price per pail.

What "100% silicone" on the label does and doesn't mean

"100% silicone" is a claim about the resin, not the solids. It doesn't mean 100% solids, and it doesn't tell you how thick the film will be. Watch the names, too. On Home Depot's shelf, Lanco's Siliconizer 1000 is listed as a silicone while Lanco Ultra Siliconizer is listed as an acrylic. Read the data sheet's resin type and volume solids before you compare prices.

Honest trade-offs

Silicone roof coating pros and cons

Silicone's strengths are water, sunlight and weather: it's rated for permanent ponding, it's UV-stable, and it goes on in conditions that stop acrylic. Its weaknesses are mechanical and long-term: low tear strength, a slick surface, dirt pickup, and a recoat path that only leads back to silicone.

Pros

Where silicone earns its price

  • Ponding water. Makers rate it for permanent ponding: GacoRoof "will not soften, bubble or degrade," and Henry 887 claims "permanent ponding water resistance." An industry guide rates silicone's ponding resistance "Excellent" and acrylic's "Poor."
  • UV and weather. Gaco calls GacoRoof "non-sacrificial" and lists "excellent durability, color stability and chalk resistance" for S42.
  • High solids. Solvent-free silicones run 92–95% solids by volume, so one coat can build 34 dry mils (S42 20-year spec).
  • Wider weather window. Henry 887 goes on from 35°F to 120°F and is rain-safe in 15 minutes. Most acrylics need 50°F.
  • Reflective when new. S42 tests at 0.87 solar reflectance and SRI 110. DOE says a reflective roof can stay more than 50°F cooler.
  • Code-recognized. ASTM D6694, IRC R905.15 and IRC Table R905.14.3 over spray foam.
Cons

What the brochures play down

  • Recoat lock-in. Acrylic over silicone ends in "peeling in sheets," and urethane over silicone is rated a no (US Made Supply). Switching later means removal.
  • Dirt pickup. Silicone "attracts dirt" (HomeGuide; American WeatherStar). S42's reflectance drops from 0.87 to 0.81 after CRRC's accelerated lab aging.
  • Slick when wet. Gaco says GacoRoof "should not be used for areas with foot traffic."
  • Low tear strength. S42 tears at 24 lbf/in; ASTM D6694's minimum is 20. Dropped tools, hail and boots show up as cuts.
  • Bleed-through on asphalt. Gaco requires a bleed-blocking base coat on SBS and recommends it on APP and BUR.
  • Vapor-open. 6.4 perms at 20 mils (S42). Gaco doesn't recommend it for cold storage buildings with a constant vapor drive.
  • Messier to apply. Solvent cleanup, pails that skin once opened, and American WeatherStar lists "challenging to spray" as a con.
Read these claims carefully"Lifetime" warranties on retail pails (Henry 887, Kool Seal Tundra) are limited warranties from the manufacturer. Read the terms: on commercial jobs, the warranty that covers leaks and labor is a system warranty issued to licensed applicators, priced per square foot and tied to a minimum dry thickness. "Blocks 80–90% of UV" and similar marketing figures come without a test method, so we haven't used them.
Head to head

Silicone vs acrylic vs urethane vs polyurea roof coating

Silicone beats acrylic under ponding water, in humid climates and in cool weather. Acrylic is cheaper and keeps future recoat options open. Urethane is tougher than both and often goes under a silicone topcoat. Sprayed polyurea is the toughest and fastest-curing, costs the most and needs a professional rig. Our own guide ranks silicone ahead of it for chronic ponding.

PropertySiliconeAcrylicUrethaneSprayed polyurea
CureMoisture cure, 1 componentWater-based, dries by evaporationMoisture cure, 1 component (aromatic base, aliphatic top)2 components, plural-component spray, sets in seconds
Roof coating standardASTM D6694ASTM D6083ASTM D6947Not named in IRC R905.15.2; ask for the product's approvals
Solids by volume (examples)69–95%55%70–77%100% (ArmorFlex UV)
Tensile strength275–500 psi500 psi725 psi aromatic; 2,300 psi aliphatic2,500–4,500 psi
Elongation196–318%600%475% aromatic; 230% aliphatic300–600%
Vapor permeance6.4 perms at 20 mils140.02 aromatic; 0.9 aliphaticNot published on our product pages
Minimum application temp35–40°F50°F40°FPer product data sheet
Permanent pondingRated for itPoorVaries by productSilicone ranked ahead for chronic ponding (our guide)
Foot trafficSlick when wet; low tearFairGoodBest; walkable in about 2 minutes
Dirt pickupHigherDepends; some have dirt-resistant techAliphatic tops resist it–
What bonds over it laterSilicone onlyAcrylic or siliconeSilicone or aliphatic urethanePolyurea, within the data sheet's recoat rules
Installed cost per sq ft$1.50–$4.50 (HG); $1.50–$2.50 (Angi)$0.50–$3.00 (HG); $0.65–$1.75 (Angi)$1.50–$4.00 (HG); $2–$5 (Angi)$3.00–$6.00 (ArmorThane guide)
Typical life10–15 yr (HG); 10–20 yr by warranty tier7–20 yr (HG); 7–12-yr retail warrantiesVaries widely by system15–25 yr (ArmorThane guide)
DIY?Yes, retail pailsYesMostly proNo, pro rig only
Example values from data sheets: silicone from GacoFlex S42 and American WeatherStar 410/412; acrylic from American WeatherStar High-Build Acrylic 212; urethane from American WeatherStar Aromatic 508 and Aliphatic 510-CA; polyurea ranges from our roof coating guide. Ponding ratings from US Made Supply and manufacturer claims. HG = HomeGuide (Apr. 2024); Angi (Aug. 2026). Individual products vary; compare data sheets.

Silicone vs acrylic roof coating

Pick silicone if water stands on the roof, if you're coating in cool or damp weather, or if you want a one-coat, high-build job. Pick acrylic if the roof drains well, the climate is moderate, the budget is tight, or you want to keep your options open. Acrylic can be recoated with silicone later; silicone can't be recoated with acrylic.

The numbers behind that. Acrylics need 50°F and rising (American WeatherStar 212) and several hours before rain or heavy dew (4–6 hours for Kool Seal's 12-year product); Henry's silicone is rain-safe in 15 minutes from 35°F. A 55%-solids acrylic leaves about 8.8 dry mils per gallon per 100 sq ft; a 95%-solids silicone leaves about 15.2 (our math). Acrylic costs less: $0.65–$1.75 per sq ft installed vs $1.50–$2.50 for silicone (Angi, 2026).

Our view: on a roof that ponds, acrylic is a false economy, because GacoRoof's maker says acrylics "degrade rapidly" under puddles and industry guidance agrees. On a roof that drains well, acrylic's lower price and recoat flexibility are real advantages, not a compromise. The elastomeric coating guide covers acrylic chemistry in more depth.

Silicone vs urethane

Urethane roof coatings are tougher: 725 psi tensile for an aromatic base coat and 2,300 psi for an aliphatic topcoat (American WeatherStar), against 275–500 psi for silicone. They're often used together. American WeatherStar's aromatic urethane "must be top coated," and silicone is one of the approved topcoats. The order matters: silicone can go on urethane, not the other way around. If the naming is confusing, our urethane vs polyurethane explainer sorts it out.

Silicone vs polyurea: our honest take

Sprayed polyurea wins on toughness (2,500–4,500 psi tensile), foot traffic, hail, chemical exposure and speed: it sets in seconds and is walkable in about two minutes. It needs a plural-component rig and a trained crew, and it costs more, $3.00–$6.00 per sq ft in our roof coating guide. Silicone wins on price and on chronic ponding; our own guide says silicone "retains its properties in sustained wet exposure" where polyurea and other coatings "would eventually soften."

So if your roof ponds, the first question is whether the slope can be fixed. If it can (with drains, crickets or tapered spray foam), either system works and traffic decides. If it can't, silicone is the safer coating. More on polyurea roofs in commercial polyurea roof coatings.

Interactive tool 1 of 4

Which roof coating fits your roof?

Four things decide it: what's on the roof now, whether water stands on it, how much foot traffic it gets, and how long you'll own the building. Answer those and the selector ranks silicone, acrylic, urethane and sprayed polyurea, with the reason behind each score.

Coating selector

Is silicone the right coating for this roof?

Rules come from manufacturer data sheets, installation specs and industry recoat guidance cited on this page. It's a screening tool, not a roof survey.

SiliconeBest fit · 75/100
Best fit

Silicone · 75/100

  • Adheres to TPO, PVC and EPDM after cleaning; aged EPDM or TPO may need an epoxy primer (GacoRoof).
  • Puddles are where silicone is strongest.
Good

Sprayed polyurea · 60/100

  • Adhesion test and the right primer for the membrane.
Poor fit

Urethane · 40/100

  • Check single-ply compatibility on the data sheet.
Poor fit

Acrylic · 35/100

  • EPDM is a common listed substrate; confirm TPO or PVC on the label.
  • Puddles that sit a day or two shorten acrylic life.

Silicone looks like a sound choice here. Before you commit, remember that every future recoat will have to be silicone too. Scores are a screening aid built from the data on this page; a roof survey, drainage check and adhesion test decide the spec. Ask a certified ArmorThane applicator to look at it.

How it scores: each system starts from a base score and gains or loses points for each answer, using the ponding, traffic, temperature, dirt, impact and recoat facts in the tables on this page. Hard stops (shingles, an existing silicone layer, gravel-surfaced roofs) override the score. Your roof's condition, drainage and warranty requirements still need an on-site look.

Service life

How long does silicone roof coating last?

Typically 10–15 years (HomeGuide), and 10–20 years when it goes on at a warranted thickness. Life tracks dry film thickness: Gaco's 2026 metal-roof specs tie 18 dry mils to a 10-year warranty, 26 mils to 15 years and 34 mils to 20 years. Thin, dirty or heavily walked jobs land at the short end.

SystemRate (gal / 100 sq ft)Wet milsDry milsWarrantySource
GacoFlex S42 over metal, 10-year1.25201810-yr material and laborSpec MR-S42-18-10
GacoFlex S42 over metal, 15-year1.75282615-yr material and laborSpec MR-S42-26-15
GacoFlex S42 over metal, 20-year2.25363420-yr material and laborSpec MR-S42-34-20
Industry rule of thumb––20 / 3010 yr / 20 yrUS Made Supply
Henry 887 (retail)1.5, one coat≈24Not publishedLifetime limitedHenry catalog 06/24
GacoRoof (retail)2.0 total, two coats≈32Not publishedSee makerGacoRoof FAQ
Kool Seal Tundra (retail)2.0, one or two coats≈32Not publishedLimited lifetimeKool Seal
Wet mils for retail products are our conversion (1 gal per 100 sq ft = 16.04 wet mils). Gaco recommends adding a 10% variance factor to reach the minimum dry thickness on warranted jobs.

Published life estimates cluster in the same range: 10–15 years (HomeGuide), "10 to 20 years or even longer" (American WeatherStar), and 15–20 years in our own roof coating guide. The honest reading is that thickness and upkeep decide which end you get.

What the warranty actually covers

Two different things are both called a warranty. A material warranty promises the coating meets its published properties; Gaco's pricing guide caps it at the original product cost. A system warranty covers leaks, including labor. Gaco issues those only to licensed applicators, as no-dollar-limit warranties for 5, 10, 15 or 20 years, at $0.05, $0.10, $0.15 or $0.20 per sq ft, with inspections and fees along the way. If a bid says "20-year warranty," ask which kind, and at how many dry mils.

What shortens silicone's life

  • Too thin. Wind, overspray and rough surfaces eat material. On granulated surfaces S42 goes from 1.25 to 1.75 gal per 100 sq ft just to cover the peaks.
  • Coating over wet insulation. Our roof coating guide is plain about it: a coating over wet insulation "will not solve the underlying problem." The IRC doesn't allow a re-cover over a water-soaked roof (R908.3.1.1).
  • Foot traffic and dropped tools. Low tear strength means cuts. Walk pads and granule paths help.
  • Dirt. It doesn't destroy the film, but it costs reflectance, which is half the reason many owners bought silicone.
  • Skipping the seams. Specs reinforce seams and fasteners with mesh and extra coating before the field coat. Leaks come back where that step was skipped.
Interactive tool 2 of 4

How much silicone roof coating do you need?

Professional systems use about 1.25–2.25 gallons per 100 sq ft for 18–34 dry mils; retail one-coat silicones call for 1.5 gallons per 100 sq ft, and two-coat products about 2. Add roughly 10% for losses. The exact number depends on the target dry mils and the product's volume solids, which is what this calculator works from.

Gallons, mils & material cost

How many gallons for my roof, at what thickness?

Pick a warranty-tier thickness or a retail product rate. The calculator converts dry mils to wet mils using volume solids, then to gallons, pails and material cost.

Parapet walls, curbs, penthouse walls
Used when target = custom
Gaco recommends 10%
$77.68 = $369 per 4.75-gal retail pail
5,000 sq ft
Area to coat
1.88
Gallons per 100 sq ft, with losses
93.8 gal
19 x 5-gal pails
$7,290
Silicone material ($1.46/sq ft)

Target 26.0 dry mils = 27.4 wet mils at 95% volume solids = 1.71 gal per 100 sq ft, plus 10% losses. For comparison, Gaco’s S42 spec (95% solids) calls for 1.75 gal per 100 sq ft for this tier, before its 10% variance.

Material list

93.8 gal of silicone

  • 93.8 gal for the field coat over 5,000 sq ft.
  • Seams, fasteners and penetrations take extra coating, mesh or sealant; specs call for an extra pass at edges and penetrations.
Warranty & pricing

26 dry mils

  • Your target lands at the 15-year tier (26 dry mils) in Gaco’s S42 metal-roof specs.
  • System warranties come from licensed applicators; Gaco lists $0.10–$0.20 per sq ft for 10–20 years ($500–$1,000 on this roof, minimums apply).
  • Price per gallon: $77.68 is a retail pail price (Henry 887, Sept. 2026). Contractors buying drums should enter their own price.

Want a sprayed system quoted with the thickness in writing? Find an ArmorThane applicator.

How we calculated this: wet mils = dry mils ÷ volume solids; gallons per 100 sq ft = wet mils ÷ 16.04 (231 cubic inches per gallon spread over 14,400 sq in); rough surfaces add 0.5 gal per 100 sq ft (the S42 sheet's 1.75 vs 1.25 rate); total = area ÷ 100 x rate x (1 + losses). Retail presets use the maker's rate directly. Granule paths add 0.5 gal and 30 lb of granules per 100 sq ft (Gaco spec). Estimates only; the product data sheet and warranty spec govern.

Wet mils, dry mils and why solids matter

One gallon spread over 100 sq ft is 16.04 mils thick while wet. When the solvent leaves, only the solids stay. So the same gallon leaves very different films depending on the product:

Volume solidsExampleDry mils per gal / 100 sq ftGal / 100 sq ft for 18 dry milsFor 26For 34
95%Solvent-free silicone (S42)15.21.181.712.23
92%High-solids silicone (412)14.81.221.762.30
69%Solvent-borne silicone (410)11.11.632.353.07
55%Acrylic (212), for comparison8.82.042.953.85
Our calculation, before losses. Gaco's own spec rates for S42 (1.25, 1.75 and 2.25) run slightly above the pure math, which is one reason to keep a variance allowance.

Check thickness as you go. A wet-film gauge during application tells you whether the rate is right while there's still time to fix it; our roof waterproofing guide lists the pull-test (ASTM D4541) and thickness checks we'd expect on any fluid-applied roof.

Interactive tool 3 of 4

Can you recoat a silicone roof?

Yes, with silicone. Cured silicone is slick and low-energy, and other coatings don't bond to it: industry guidance says acrylic over silicone ends in "peeling in sheets" and rates urethane over silicone a no. Our own guide puts it as "once a silicone roof, always a silicone roof." Clean it, test adhesion, then recoat with silicone.

Recoat compatibility checker

Can this coating go over what's on my roof now?

Pick the existing surface and the coating you're considering. You'll get a verdict, the prep it needs and where the rule comes from.

NoAcrylic over this surface
Why

Acrylic

Acrylic doesn’t reliably bond to cured silicone; the field result is “peeling in sheets” (US Made Supply).

Prep

What to do next

  • To change chemistry, the silicone has to be removed. Otherwise, recoat with silicone.

Other options over this surface: Silicone: yes, with prep · Urethane: no · Sprayed polyurea: no. Summary of manufacturer listings and industry guidance; the new product’s data sheet and an adhesion test decide.

Recoating silicone with silicone, step by step

  1. Confirm it's sound

    Cut out and replace wet insulation and delaminated areas first. A recoat seals the surface; it doesn't dry the roof.

  2. Clean hard, then let it dry

    Gaco's spec uses a roof cleaner and a power washer above 3,000 psi, rinsing high to low, and treats algae and mildew with 1 part household bleach to 3 parts water. The Roof Coatings Manufacturers Association's point stands: "A primer is no substitute for thorough cleaning."

  3. Test adhesion

    Coat test patches and pull them after cure. GacoRoof's kit reads out in 24 hours; on bigger jobs an applicator can run pull tests (ASTM D4541).

  4. Abrade or tie-coat if the maker says so

    Industry guidance says silicone over silicone works "with abrasion or tie-coat." Use the new product maker's procedure; don't mix brands blind.

  5. Detail, then coat the field

    Rebuild failed seams and fasteners with mesh and silicone sealant, then apply the field coat at the rate for your target dry mils.

How to tell if a roof is already silicone

Start with paperwork: the original bid, spec sheet, warranty or invoice. On the roof, clues (not proof) are a rubbery, slick surface that water beads on tightly, while an aged acrylic often leaves white chalk on a fingertip. If there's any doubt, assume silicone until an adhesion test says otherwise. Coating the wrong chemistry over silicone is the classic failure: it looks fine for a season, then lets go in sheets.

Before you choose siliconeThink 15 years ahead. If you might want a different system later (sprayed polyurea for a roof that turns into a work area, spray foam to add insulation, or anything other than silicone), the silicone will have to come off first. We couldn't find published removal costs, so get that number as part of any long-term plan.
Interactive tool 4 of 4

Silicone roof coating cost in 2026

Installed silicone runs $1.50–$4.50 per sq ft in HomeGuide's 2024 survey and $1.50–$2.50 in Angi's August 2026 update; our roof coating guide uses $2.50–$5.50 for commercial systems. A one-coat retail silicone costs about $1.17 per sq ft in material at current pail prices. System warranties add $0.05–$0.20 per sq ft.

ItemPublished figureDateSource
Silicone, installed$1.50–$4.50 / sq ftApr 2024HomeGuide
Silicone, installed$1.50–$2.50 / sq ftAug 2026Angi
Silicone, commercial system$2.50–$5.50 / sq ft2026ArmorThane roof coating guide
Silicone recoat$1.50–$3.00 / sq ft2026ArmorThane roof coating guide
Acrylic, installed$0.65–$1.75 / sq ftAug 2026Angi
Polyurethane, installed$2–$5 / sq ftAug 2026Angi
Sprayed polyurea$3.00–$6.00 / sq ft2026ArmorThane roof coating guide
Materials vs labor (all coatings)$0.15–$2.75 materials; $0.50–$3.00 labor / sq ftApr 2024HomeGuide
Gaco system warranty, 10 / 15 / 20 yr$0.10 / $0.15 / $0.20 per sq ft (min. $750 / $1,125 / $1,500)Jun 2025Gaco pricing guide
Ranges are as published; they vary with roof size, prep, repairs, thickness and access.

DIY silicone: what a pail really costs per square foot

ProductPailPricePer gallonCoverageMaterial per sq ft
Henry 887 Tropi-Cool (silicone)4.75 gal$369.00$77.681.5 gal / 100 sq ft, one coat$1.17
Lanco Siliconizer 1000 (silicone)5 gal$298.61$59.72Check the label–
Gardner 100% Silicone Coat-N-Seal4.75 gal$129.00$27.16Not on the product page–
Lanco White-Seal (acrylic), for comparison5 gal$79.98$16.001 gal / 100 sq ft per coat (typical acrylic), two coats≈$0.32
Henry and Lanco prices observed at Home Depot on Sept. 26, 2026; Gardner from its store. Per-sq-ft figures are our math. A low pail price can mean lower solids or a thinner rate, so compare cost per dry mil.
Life-cycle cost

Silicone vs acrylic vs urethane vs polyurea over the years you'll own it

Defaults are midpoints of the published ranges above. Change any cost or life to match your bids. Each system is recoated at the end of its life at a share of its first cost.

Our guide: silicone recoat ≈55–60% of first cost
0 = plain dollars
Acrylic
Lowest total on these inputs
$32,000
Silicone, total
2
Silicone coats you pay for
$0.11
Silicone, per sq ft per year of protection
Silicone (2 coats)
$32,000
Acrylic (3 coats)
$26,400
Urethane (2 coats)
$56,000
Sprayed polyurea (2 coats)
$72,000

Over 30 years on 10,000 sq ft. Per sq ft per year of protection: silicone $0.11, acrylic $0.09, urethane $0.19, sprayed polyurea $0.18. Still has life left when you sell: sprayed polyurea (about 10 years left). Acrylic only wins if it really lasts 10 years; on a roof that ponds, try 5. This doesn’t price foot traffic, hail or chemicals, or the cost of removing silicone if you ever switch systems. Estimates only.

How we calculated this: coats = years ÷ life, rounded up; total = area x [first cost + (coats − 1) x recoat share x first cost], each recoat discounted by (1 + rate)^year if you enter a rate. "Per year of protection" divides the total by the years of service you actually bought, which credits a coating that still has life left when you sell. Default costs are range midpoints: acrylic, silicone and urethane from Angi (Aug. 2026), polyurea from our roof coating guide. Default lives: acrylic 10 years (Henry's 10-year acrylic warranty; Angi's "resealing every 10 years"), silicone 15 (Gaco's 26-mil tier), polyurea 20 (midpoint of our guide's 15–25), urethane 15 (our assumption; published figures vary widely). The recoat share is derived from our guide's silicone recoat range ($1.50–$3.00) against its install range ($2.50–$5.50).

What the defaults show, honestly: on a roof that drains well, acrylic is cheapest on paper and silicone is second. Set acrylic's life to 5 years, which is closer to what a ponding roof gives it, and its total nearly doubles. Polyurea rarely wins this math on price alone; its case is foot traffic, hail, chemicals and mechanical abuse, which a spreadsheet doesn't price.

Standing water with plants growing in it on a flat roof, a sign of chronic ponding
Water that's still there two days after rain is ponding. Plants mean it's been there much longer.
Standing water

Silicone roof coating and ponding water

Silicone is the coating most often chosen for ponding because it's rated to sit under standing water without softening. But ponding is a symptom, not a feature. Water that remains 48 hours or more after rain adds weight, collects dirt that kills reflectance, and often points to a sagging deck or blocked drains.

What the code says about slope

The IRC requires liquid-applied roofing to have a design slope of at least ¼ inch per foot (2%) (R905.15.1), and spray foam roofs the same (R905.14.1). A coating doesn't create slope. Every inch of standing water also weighs about 5.2 lb per square foot (our math from the weight of water), which adds up quickly across a large pond.

Fix the slope first, then coat

Clear drains and scuppers, add crickets, or build slope with tapered spray foam. Our ArmorFoam Roof 200 page describes exactly that: a closed-cell roofing foam that lets applicators "create positive slopes, improve drainage, and eliminate ponding," then gets a compatible topcoat. If the slope can't be fixed, silicone is the right coating to live with it. More in our flat roof waterproofing guide.

Installation

How silicone roof coating is applied

Inspect and dry out the roof, clean it thoroughly, repair seams and fasteners, test adhesion and prime only where the test says so, then apply the field coat at the rate for your target dry mils, with an extra pass at edges and penetrations. Most of the work, and most of the warranty risk, is in the prep.

  1. Inspect and find wet insulation

    Core cuts or infrared scans locate wet insulation, which gets cut out and replaced. Check drains, flashings and the deck for deflection.

  2. Clean

    Roof cleaner plus a power wash (Gaco's spec: above 3,000 psi), rinsing from the high point down. Treat algae and mildew with 1:3 bleach and water. Let it dry fully.

  3. Repair seams, fasteners and flashings

    Gaco's metal spec embeds 4-in. polyester mesh in coating at 1.5 gal per 100 sq ft over seams, or uses silicone sealant at 64 wet mils. Tighten or replace loose fasteners; wire-brush and prime rust.

  4. Adhesion test, then prime only if needed

    Epoxy primer at 1 gal per 300 sq ft or a bonding primer at 200–250 sq ft per gallon, only where the test calls for it.

  5. Block bleed-through on asphalt

    SBS needs a bleed-blocking base coat before silicone; APP and BUR get one recommended (Gaco: 100 sq ft per gallon, 6 dry mils). Not over gravel-surfaced BUR.

  6. Apply the field coat

    Roll or spray at the specified rate, check wet mils with a gauge, and add an extra pass at edges, penetrations and seams.

  7. Add traction where people walk

    Broadcast white roofing granules into a 0.5 gal per 100 sq ft coat at 30 lb per 100 sq ft on service paths, or install walk pads.

  8. Let it cure

    S42 allows light foot traffic after 24–48 hours; Gaco's 20-year spec keeps all traffic off for 3 days.

Weather windows by product

ProductTemperatureRainOther
Henry 887 (silicone)35–120°FRain-safe in 15 minOne coat
Kool Seal Tundra (silicone)Not stated on pageRain-safe in 60 minRecoat at 6 h; full cure 72 h at 70°F / 50% RH
GacoFlex S42 (silicone)Above 40°F and 5°F over dew point, risingNo rain within 1 hLight traffic after 24–48 h
GacoFlex S20 (silicone)Per data sheetCan be rained on within 2 hOne coat on smooth surfaces
American WeatherStar 410 (silicone)40°F minimumNo rain within 1 hRecoat within 24 h
American WeatherStar 212 (acrylic)50°F minimum, air and surfaceNot if rain, fog or dew is imminentNot within 5°F of dew point
Kool Seal 12-year (acrylic)Not stated on page4–6 h before rain or heavy dewTwo coats
From each manufacturer's product page or data sheet.

DIY or professional?

A small, simple roof is a reasonable DIY job with a retail silicone and a roller: GacoRoof's maker says its product is too thick to spray and needs two coats, and Henry 887 is a one-coat product. Mark the second coat with chalk lines or a tinted coat so you don't miss spots. For mobile homes and RVs, our mobile home roof coating guide walks through the smaller-roof version.

Commercial roofs are a different job. Manufacturer system warranties go only to licensed applicators, pro silicone is usually sprayed (Gaco and American WeatherStar both publish spray guides), and the prep (wet-insulation surveys, seam work, adhesion testing) is where the money goes. Get the dry-mil target and the warranty type in writing.

Upkeep

Maintaining a silicone roof

Keep it clean, keep people on the walk paths, fix cuts with silicone, and recoat with silicone before the film wears through. That's most of it. Silicone resists chalking (Gaco lists chalk resistance for S42), so the usual threats are dirt, mechanical damage and whatever is happening at the seams and drains.

  • Wash it. Low pressure only on the finished coating: GacoRoof's maker allows washing below 2,500 psi. American WeatherStar suggests every 6–12 months to keep reflectivity up.
  • Inspect after storms and service calls. Look for cuts around rooftop units, at walk paths and where hail hits.
  • Repair like with like. Silicone sealant or the same silicone coating. Nothing else will bond to it.
  • Keep drains clear. Silicone tolerates ponding, but debris-blocked drains make ponds bigger and dirtier.
  • Keep the warranty alive. System warranties come with inspections and fees; Gaco's guide charges for the fifth and later inspections and for transfers.
  • Plan the recoat. Our guide puts a silicone recoat at $1.50–$3.00 per sq ft at 15–20 years. It's cheaper than tear-off only while the roof underneath is still dry.
Where we fit

Where ArmorThane fits, and where it doesn't

We don't make silicone roof coating. If your roof ponds and the slope can't be fixed, or the budget calls for a restoration coat you can roll yourself, a silicone from a roof-coatings manufacturer is a sound choice, and a good applicator will tell you so.

Our materials earn their keep where silicone struggles. Sprayed ArmorFlex UV is a 100% solids aliphatic polyurea formulated to be color-stable as a durable protective or waterproof coating: the kind of membrane you want where a roof takes foot traffic, hail, chemicals or equipment. Spray foam roofing with ArmorFoam Roof 200 adds insulation and builds the slope a ponding roof is missing, then takes a protective topcoat. Our roof coating guide calls polyurea the default for spray foam topcoats and for metal roofs with foot traffic.

And one thing we won't do: spray polyurea over an existing silicone roof. It's the same lock-in described above, and it applies to our products too. The silicone comes off first, or the roof stays silicone.

Find a certified applicator →Read the roof coating guide
100% solids

ArmorFlex UV

Two-component aliphatic polyurea, 1:1, fast-set and color-stable, for exposed waterproof coatings that need to hold their color.

2.5–3.0 pcf

ArmorFoam Roof 200

Closed-cell roofing foam that self-flashes penetrations and builds positive slope to eliminate ponding.

≈2 min

Walkable

Sprayed polyurea roofs are walkable in roughly two minutes and serviceable within a day.

For roofing contractors

Already coating roofs? Add polyurea and foam.

A plural-component rig lets the same crew spray polyurea roofs, foam roofing, floors and liners, the jobs where silicone isn't the answer. We supply the material, build the rigs and train your crew. Not a franchise: no franchise fee, no royalties, and startup packages from $25,000.

Become an applicatorSee the spray rigs

Questions first? Call (417) 831-5090 (US) or 780-444-6200 (Canada).

Straight answers

Silicone roof coating FAQ

What are the pros and cons of silicone roof coating?

Pros: it's rated for permanent ponding water, it's UV-stable, solvent-free versions run 92–95% solids by volume, and it can go on from 35–40°F with rain-safe times as short as 15 minutes (Henry 887). Cons: it picks up dirt and loses some reflectance, it's slick when wet, its tear strength is low (24 lbf/in on one leading product), and only silicone reliably bonds to it at recoat time.

Is silicone or acrylic roof coating better?

Silicone is better on roofs that pond water, in humid climates and in cool-weather work, since acrylics need 50°F or warmer and rate "Poor" under ponding in industry guidance. Acrylic is cheaper ($0.65–$1.75 per sq ft installed vs $1.50–$2.50 for silicone, Angi 2026) and keeps your options open, because silicone can go over acrylic later but not the reverse. On a roof that drains well, acrylic is a fair choice.

How long does silicone roof coating last?

Typically 10–15 years (HomeGuide), and 10–20 years when applied to a warranted thickness. GacoFlex S42 specs tie 18 dry mils to a 10-year warranty, 26 mils to 15 years and 34 mils to 20 years. Dirt, foot traffic, thin spots and coating over wet insulation shorten it. See the lifespan table.

What is the best silicone roof coating?

Judge the data sheet, not the brand: volume solids (92–95% for solvent-free products vs 69% for one solvent-borne product we checked), compliance with ASTM D6694, tensile and tear values, published reflectance, and a warranty tied to a stated dry-mil thickness. Then buy enough to hit that thickness. The calculator converts mils to gallons.

Can you put acrylic or elastomeric coating over silicone?

No. Acrylic doesn't reliably bond to cured silicone; one industry guide says the result is "peeling in sheets," and it rates urethane over silicone as a no too. Our own roof coating guide puts it as "once a silicone roof, always a silicone roof." Switching chemistries means removing the silicone first.

Can you recoat a silicone roof?

Yes, with silicone. Clean it thoroughly, treat any algae or mildew, let it dry, run an adhesion test, and abrade or use the manufacturer's tie-coat where they call for it. Several silicones, including Henry 887 and GacoRoof, list previously coated or silicone roofs as acceptable substrates. The recoat checker covers other combinations.

Do I need a primer before silicone roof coating?

Often not, but test first. GacoFlex S42 is designed to skip primer on most substrates, yet Gaco still says to always perform an adhesion test; aged EPDM and TPO may need an epoxy primer, rusty metal needs a rust primer, and SBS modified bitumen needs a bleed-blocking base coat. The Roof Coatings Manufacturers Association adds that a primer is no substitute for thorough cleaning.

How much silicone roof coating do I need per square foot?

Professional systems run about 1.25–2.25 gallons per 100 sq ft for 18–34 dry mils (GacoFlex S42), plus about 10% for losses. Retail one-coat silicones such as Henry 887 call for 1.5 gallons per 100 sq ft, and two-coat products such as GacoRoof use 1 gallon per 50 sq ft for the finished job. A 1,000 sq ft roof needs roughly 14–25 gallons, depending on the product and thickness.

Can you walk on a silicone roof coating?

For service visits, yes, carefully. Silicone is slick when wet, and GacoRoof's maker says not to use it where there's regular foot traffic. Specs call for light traffic only after 24–48 hours of cure and no traffic for 3 days on a warranted job. Add walk pads or a granule broadcast (0.5 gal and 30 lb of granules per 100 sq ft) on service paths.

Can silicone roof coating be used on shingles?

No. Henry says its 887 silicone is "not recommended over shingles of any kind," GacoRoof excludes 3-tab and architectural shingles, and Kool Seal's silicone is "not for use on roof shingles." Silicone is built for low-slope metal, single-ply, smooth BUR, modified bitumen, concrete and spray foam roofs.

How much does silicone roof coating cost?

HomeGuide puts installed silicone at $1.50–$4.50 per sq ft (2024) and Angi at $1.50–$2.50 (August 2026); our own roof coating guide uses $2.50–$5.50 for commercial systems. DIY material for a one-coat retail silicone works out to about $1.17 per sq ft at a $369 4.75-gallon pail. Manufacturer system warranties add $0.05–$0.20 per sq ft.

Can silicone roof coating be applied in cold weather or before rain?

It tolerates both better than acrylic. Henry 887 goes on from 35°F to 120°F and is rain-safe in 15 minutes; Gaco wants the surface above 40°F and 5°F over the dew point, with no rain for an hour. Acrylics generally need 50°F and several dry hours. Silicone cures slower in cold, dry air, so plan the cure time accordingly.

Can you pressure wash a silicone roof?

Yes, gently. GacoRoof's maker allows low-pressure washing below 2,500 psi, and American WeatherStar suggests washing every 6–12 months to keep reflectivity up. Prep before a recoat is more aggressive: Gaco's spec uses a cleaner and a power washer above 3,000 psi on the existing roof.

AT
ArmorThane Technical Team · Springfield, Missouri
Written from manufacturer data sheets, installation specs, code text and published cost surveys by a manufacturer that makes polyurea and spray foam, not silicone. Last updated September 26, 2026.

Methodology and sources

Product properties come from each manufacturer's current data sheet or installation specification, quoted as published; individual products vary. Code text is the 2015 IRC chapter 9 as adopted by Seattle. Costs are as published by HomeGuide (April 2024), Angi (August 2026) and our roof coating guide; retail pail prices were observed on September 26, 2026. Conversions (wet to dry mils, gallons, cost per square foot) and the tool outputs are our calculations and are estimates, not a substitute for a roof survey or the product's warranty specification.

  1. ASTM D6694, liquid-applied silicone coating used in SPF roofing (scope): store.astm.org/d6694_d6694m-15.html
  2. 2015 IRC chapter 9 (R905.14, R905.15, R908) as adopted in the Seattle Residential Code (PDF): seattle.gov/documents/Departments/SDCI/Codes/SeattleResidentialCode/20
  3. Roof Coatings Manufacturers Association, glossary: roofcoatings.org/glossary/
  4. Roof Coatings Manufacturers Association, FAQs: roofcoatings.org/faqs/
  5. U.S. DOE Energy Saver, cool roofs: energy.gov/energysaver/cool-roofs
  6. GacoFlex S42 sales sheet and data (2024, PDF): gaco.com/wp-content/uploads/2020/05/GacoFlex-S42-Sales-Sheet.pdf
  7. GacoFlex S42 over metal roof, 10-year spec MR-S42-18-10 (rev. 05/2026, PDF): gaco.com/wp-content/uploads/2021/03/MR-S42-18-10_-_GACOFLEX_S42_SERIES
  8. GacoFlex S42 over metal roof, 15-year spec MR-S42-26-15 (PDF): gaco.com/wp-content/uploads/2021/03/MR-S42-26-15_-_GACOFLEX_S42_SERIES
  9. GacoFlex S42 over metal roof, 20-year spec MR-S42-34-20 (PDF): gaco.com/wp-content/uploads/2021/03/MR-S42-34-20_-_GACOFLEX_S42_SERIES
  10. GacoFlex warranty pricing guide (June 2025, PDF): gaco.com/wp-content/uploads/2019/04/Gaco_Warranty_Pricing_Guide.pdf
  11. GacoFlex S42 product page: gaco.com/product/gacoflex-s42/
  12. GacoFlex S20 product page: gaco.com/product/gacoflex-s20/
  13. GacoRoof FAQs: gaco.com/gacoroof-faqs/
  14. Gaco, silicone roof coating systems: gaco.com/roofing/silicone-roof-coating-systems/
  15. American WeatherStar, pros and cons of silicone roof coatings: americanweatherstar.com/insights/pros-and-cons-of-silicone-roof-coatin
  16. American WeatherStar Silicone 410 data sheet (PDF): americanweatherstar.com/doc-library/product-data-sheets/product-data-s
  17. American WeatherStar High-Solids Silicone 412 data sheet (PDF): americanweatherstar.com/doc-library/product-data-sheets/product-data-s
  18. American WeatherStar High-Build Acrylic 212 data sheet (PDF): americanweatherstar.com/doc-library/product-data-sheets/product-data-s
  19. American WeatherStar Aromatic Urethane 508 data sheet (PDF): americanweatherstar.com/doc-library/product-data-sheets/product-data-s
  20. American WeatherStar Aliphatic Urethane 510-CA data sheet (PDF): americanweatherstar.com/doc-library/product-data-sheets/product-data-s
  21. Henry retail product catalog (06/24, PDF): dam.carlisle.com/asset/1a7b0464-4df2-41c3-b0f0-74a1feb6431d/Retail-Pro
  22. Henry 887 Tropi-Cool 100% silicone roof coating: henry.com/residential/products/residential-roof-coatings/white-roof-co
  23. Kool Seal Tundra silicone roof coating: koolseal.com/product/tundra-silicone-rubberized-white-roof-coating/
  24. Kool Seal Premium 12-year elastomeric roof coating: koolseal.com/product/premium-elastomeric-finish-coat-12yr/
  25. Gardner 100% Silicone Flat Roof Coat-N-Seal SK-8245: gardnercoatings.com/products/gardner-flat-roof-coat-n-seal-sk-8245
  26. APOC silicone coatings: apoc.com/collections/silicone-coatings
  27. Home Depot, roof coatings (prices observed Sept. 26, 2026): homedepot.com/b/Building-Materials-Roofing-Commercial-Roofing-Roof-Coa
  28. US Made Supply, what is an elastomeric roof coating (May 2026): usmadesupply.com/resources/guides/what-is-an-elastomeric-roof-coating
  29. HomeGuide, roof coating cost (Apr. 2024): homeguide.com/costs/roof-coating-or-sealing-cost
  30. Angi, roof coating cost per square foot (Aug. 2026): angi.com/articles/how-much-does-roof-coating-cost-square-foot.htm
  31. ArmorThane, roof coating guide: armorthane.com/knowledge-center/roof-coating-guide/
  32. ArmorThane, roof waterproofing guide: armorthane.com/protective-coatings/roofing/
  33. ArmorThane, commercial polyurea roof coatings: armorthane.com/armorthane-commercial-polyurea-roof-coatings/
  34. ArmorThane, ArmorFlex UV aliphatic polyurea: armorthane.com/products/armorline-products/high-pressure/armorflex-uv/
  35. ArmorThane, ArmorFoam Roof 200: armorthane.com/products/armorfoam-products/roof-200/

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