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ARMORTHANE PROTECTING YOUR WORLD

PROTECTING YOUR WORLD

ARMORTHANE PROTECTING YOUR WORLD

Waterproof Paint:
What Works, Where
& How Much

Masonry waterproofers, elastomerics, roof coatings and membranes compared, with a water-pressure check and a film-thickness calculator so you buy the right product in the right amount.
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Paint not holding the water back? Talk to a polyurea pro.

Tell us the surface, where the water comes from and roughly how big the area is. A certified ArmorThane applicator near you will follow up.

  • Foundations and retaining walls
  • Planters, ponds and tanks
  • Decks, roofs and balconies
  • Seamless spray-applied membranes
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Step 1 of 3
15 psi
Hydrostatic rating of a top masonry waterproofer (≈33 ft of water)
Sika DRYLOK Extreme PDS, 2026
$2–$10
Waterproof paint or sealing, per sq ft installed
HomeGuide, 2026
100%
Min. elongation, acrylic roof coating
ASTM D6083 via IIBEC
1–10 perms
Typical latex paint vapor class (Class III)
InterNACHI

Waterproof paint is a catch-all name for coatings that keep liquid water out of whatever they cover: masonry waterproofers for basement walls, elastomeric coatings for stucco and block, roof coatings, and thick rubbery membranes. Some are genuinely waterproof within limits, such as a basement waterproofer rated against 15 psi of water pressure. Others are just water-resistant paint with a confident label. We manufacture spray-applied polyurea membranes, which sit at the heavy end of this range, and we will be the first to say most walls do not need them. This guide shows which waterproof paint fits which job, how much to buy, and where paint stops working.

Quick answer

For damp interior basement walls, use a masonry waterproofer rated for hydrostatic pressure and apply two coats to bare masonry. For above-grade stucco, block and masonry, use an elastomeric wall coating that bridges hairline cracks and still breathes. For low-slope roofs, use a roof coating that meets a standard such as ASTM D6083. For flowing leaks, moving cracks, ponds, tanks and anything you walk on, paint is the wrong tool: you need repairs, a drainage fix or a membrane such as polyurea.

What's in this guide
  1. 1Types of waterproof paint
  2. 2Comparison table
  3. 3Waterproof paint selector (tool)
  4. 4Hydrostatic pressure check (tool)
  5. 5Film thickness and gallons calculator (tool)
  6. 6How to apply waterproof paint
  7. 7Where waterproof paint fails
  8. 8Waterproof paint FAQ
Product families

Types of waterproof paint and what each is built for

Basement walls

Masonry waterproofer

Thick latex or cementitious paints that fill the pores of block and concrete from the inside. Sika's 2026 data sheet for DRYLOK Extreme lists resistance to 15 psi (ASTM D7088), about a 33 ft column of water, two coats at 75 sq ft per gallon for the first and 75–100 for the second, and new concrete cured 28 to 30 days or below pH 10. It is not for floors with foot traffic or for fishponds.

Above-grade walls

Elastomeric wall coating

A very thick, stretchy acrylic. Dunn-Edwards' Enduralastic 5, a typical example, goes on at 26–30 mils wet for 11–13 mils dry, covers about 25–75 sq ft per gallon, stretches 266% and has a perm rating of 6.0. It bridges hairline cracks in stucco and block while letting the wall breathe. Not for below grade.

Roofs

Elastomeric roof coating

Acrylic, silicone or urethane coatings for low-slope roofs. ASTM D6083 for acrylic roof coatings requires at least 100% elongation, 200 psi tensile strength, 60% weight solids and 50% volume solids, and no more than 50 perms at 20 mils. Ponding water is the main enemy of acrylics. See our spray-on roof coating guide.

Membranes

Liquid rubber, polyurethane, polyurea

Thick, continuous membranes that resist standing water and, in the case of spray polyurea, impact and abrasion too. They are the right answer for foundations from the outside, planters, ponds, tanks and decks. Compare them in our liquid-applied waterproofing membrane guide.

"Waterproof" exterior paint for wood and metalOrdinary exterior latex and enamel paints shed rain but are rated as water-resistant, not waterproof. InterNACHI lists latex and enamel paint as Class III vapor retarders, between 1 and 10 perms, which is exactly why they work on siding: moisture can still get out.
Compare

Waterproof paint comparison: film, stretch, pressure

Sort by any column. Figures are from the example product data sheets and standards named in the caption; other brands in the same family will differ.

TypeTypical useCoverage, sq ft/galDry film, milsElongationHandles water pressureFoot traffic
Exterior latex paintSiding, trimPer labelThinLowNoNo
Masonry waterprooferInterior basement walls75 (1st), 75–100 (2nd)Not publishedLowRated 15 psi (DRYLOK Extreme)No
Elastomeric wall coatingStucco, block, masonry above grade25–7511–13266%NoNo
Acrylic roof coatingLow-slope roofsBy thickness20 (test film)≥100% (D6083)Not pondingMaintenance only
Spray polyurea membraneFoundations, planters, ponds, tanks, decksBy thicknessThick, system-specifiedHighYes, as a membraneYes
Sources: Sika DRYLOK Extreme PDS (Aug 2026); Dunn-Edwards Enduralastic 5 PDS; ASTM D6083 summary by IIBEC; InterNACHI vapor retarder classes. Polyurea row is qualitative; thickness and properties depend on the specific product and system.
Tool 1

Which waterproof paint does your job need?

Choose the surface and where the water comes from. The selector points you to a product family and flags the jobs where no paint will do.

Selector

Waterproof paint selector

Rules follow the product limits on the data sheets: masonry waterproofers for negative-side basement walls, elastomerics for above-grade walls, roof coatings for drained roofs, membranes for immersion, soil contact, traffic and moving cracks.

Also
—
—
Is paint enough?
—
First step

Tool 2

Can waterproof paint hold back the water pressure?

Fresh water presses on a wall at about 0.433 psi for every foot of depth (its weight, 62.4 lb per cubic foot, spread over 144 square inches). If the soil around your basement is saturated to 6 ft, the base of the wall sees roughly 2.6 psi. A masonry waterproofer rated at 15 psi has the numbers on its side; the real-world failures come from cracks, the floor-wall joint, and paint that was put over old paint or efflorescence, which voids the warranty on products like DRYLOK.

Calculator

Hydrostatic pressure check

Pressure (psi) = depth of saturated soil or water (ft) × 0.433. Compared with the coating's published rating, for example 15 psi for DRYLOK Extreme per Sika's data sheet.

Grade to floor, if soil gets soaked
From the product data sheet
What you see
—
Pressure at wall base
—
Rating ÷ pressure
—
Verdict

Tool 3

How much waterproof paint? Work from film thickness

Waterproofing performance comes from thickness, not from the number of coats. Thick coatings are specified in mils of dry film, and the math is fixed: one US gallon is 231 cubic inches, which spreads to 1,604 sq ft at 1 mil if it were 100% solids. Divide by the mils you need and multiply by the volume solids on the data sheet. The presets use the Dunn-Edwards Enduralastic 5 film build (26–30 mils wet for 11–13 dry, roughly 43% solids by volume) and the ASTM D6083 roof test film of 20 mils at the 50% volume-solids minimum.

Calculator

Dry film thickness to gallons

Coverage (sq ft/gal) = 1,604 × volume solids ÷ dry mils. Wet film = dry mils ÷ volume solids. Gallons = area ÷ coverage × (1 + loss allowance).

On the product data sheet
Texture, porosity, overspray; your call
—
Coverage at target film
—
Wet film to apply
—
Gallons incl. loss
—
Material cost

Check with a wet-film gaugeA notched wet-film gauge costs a few dollars and is the only way to know you are actually putting on the film the data sheet calls for. Press it into the wet coat every few square yards; most premature failures we inspect were simply too thin.
Application

How to apply waterproof paint on masonry

  1. Find and fix the water path

    Clean gutters, extend downspouts and check that soil slopes away from the house. Patch cracks and the floor-wall joint with hydraulic cement or a crack-repair product before you paint.

  2. Get to bare, sound masonry

    Masonry waterproofers are designed to bond into bare pores. DRYLOK's warranty applies to properly prepared bare masonry, and applying over existing coatings voids it. Wire-brush efflorescence and loose material.

  3. Respect cure and temperature

    New concrete needs 28 to 30 days or a pH below 10 (DRYLOK Extreme). Apply at 50°F or higher; elastomerics such as Enduralastic 5 also stop below 50°F.

  4. Work it into the pores

    Use a stiff masonry brush or a heavy-nap roller and push the first coat into every pinhole in the block. Pinholes are where leaks come back.

  5. Build the film in two coats

    Recoat at the data-sheet interval: about 2 hours for DRYLOK Extreme, 24 hours for Enduralastic 5. Check thickness with a wet-film gauge as you go.

  6. Give it time before judging

    Let it cure fully, then watch it through a few heavy rains. Persistent wet spots at the same place usually point to a crack or joint, not the paint.

Honest limits

Where waterproof paint fails and what to use instead

Paint won't fix it

Active leaks and wet basements

Running water, a wet floor-wall joint or a cracked wall needs drainage and repairs first. HomeGuide puts full basement waterproofing at $6,000–$18,000 on average, which tells you how different that job is from a coat of paint. Start with our concrete waterproofing guide.

Paint won't fix it

Below-grade from the outside

Soil-side foundation walls need a membrane that can stand permanent soil contact and bridge cracks. Spray polyurea is one option; see foundation waterproofing.

Different product

Ponds, fountains and tanks

Masonry waterproofers such as DRYLOK are not for fishponds. Immersion needs a liner-grade coating, see our pond liner guide, and drinking water needs a coating certified to NSF/ANSI 61, such as our AquaShield.

Different product

Floors, decks and walkways

Waterproofers and elastomerics are not made for foot traffic. Walking surfaces need a floor-rated coating with texture; see anti slip paint, or cool deck coating around pools.

Do not seal a wall that needs to breathePainting the inside of a basement with a low-perm coating while ground moisture keeps coming from outside can push that moisture somewhere else, often into finished walls or the floor-wall joint. For clear, breathable protection of above-grade brick and block, a masonry sealer is often the better first step than paint.
When paint isn't enough

Seamless polyurea waterproofing, sprayed by certified pros.

ArmorThane applicators spray polyurea membranes on foundations, planters, ponds, tanks, decks and roofs. Tell us what is leaking and we will tell you honestly whether you need a membrane or just the right paint.

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FAQ

Waterproof paint questions

Is waterproof paint really waterproof?

Some of it is, within published limits. A masonry waterproofer like DRYLOK Extreme is tested to resist 15 psi of water pressure on properly prepared bare masonry. Ordinary exterior paint is water-resistant, not waterproof. No paint fixes cracks, failed joints or poor drainage.

What is the best waterproof paint for basement walls?

A masonry waterproofer with a published hydrostatic pressure rating, applied in two coats to bare, clean block or concrete. Fix cracks and the floor-wall joint first, and make sure gutters and grading send water away from the house.

Can I use waterproof paint on a basement floor?

Generally no. DRYLOK Extreme, for example, is not recommended for horizontal surfaces with foot traffic. Floors need a floor-rated coating such as epoxy, polyaspartic or polyurea, chosen with the slab's moisture in mind.

What is the difference between elastomeric paint and waterproof paint?

Elastomeric coatings are a type of waterproofing paint for above-grade walls and roofs. They go on very thick (11–13 mils dry for Enduralastic 5) and stretch, so they bridge hairline cracks while still letting vapor out. Masonry waterproofers are made to resist water pressure from the negative side of basement walls.

How long does waterproof paint last?

It depends on the product and the prep. Sika offers a 15-year limited warranty on DRYLOK Extreme when two coats go on properly prepared bare masonry. Elastomerics and roof coatings last as long as their film thickness holds up, which is why applying the full specified mils matters.

How much does waterproof paint cost?

HomeGuide's 2026 figure for waterproof paint or concrete sealing is $2 to $10 per square foot including labor and materials. Material alone depends on how many gallons the film thickness requires; the calculator above shows the math.

Can waterproof paint go over existing paint?

Masonry waterproofers need bare masonry to bond into; DRYLOK states that applying over existing coatings voids its warranty. Elastomerics can go over sound, compatible paint with the right primer. Test adhesion on a small area first.

Is waterproof paint safe for a pond or water tank?

Only if the product is rated for it. Many masonry waterproofers exclude fishponds. For potable water, look for NSF/ANSI 61 certification, as with ArmorThane AquaShield.

AT
Written by the ArmorThane technical team. We have manufactured polyurea, polyurethane and polyaspartic coatings in Springfield, Missouri since 1989 and train certified applicators across North America. Product figures come from the manufacturer data sheets and standards listed below. Updated October 2026.

Sources

  1. Sika USA, DRYLOK Extreme product data sheet (Aug 2026, v01.04): usa.sika.com/.../drylok-extreme.pdf
  2. Dunn-Edwards, Enduralastic 5 elastomeric wall coating PDS: dunnedwards.com/.../EN-EDLV10-PDS.pdf
  3. IIBEC, ASTM D6083 Standard Specification for Liquid Applied Acrylic Coating Used in Roofing: iibec.org/publication-post/astm-d-6083...
  4. InterNACHI, Vapor Diffusion Retarder Inspection (vapor retarder classes): nachi.org/vapor-retarder-inspection.htm
  5. HomeGuide, basement waterproofing cost (2026): homeguide.com/costs/basement-waterproofing-cost
  6. Petersen Products, calculating PSI from feet of head (0.433 psi per ft): petersenproducts.com/articles/how-to-calculate-pipeline-pressure-psi-from-feet-of-head...

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