Will a coating alone keep a basement dry?

Not against standing water. A coating resists moisture passing through the wall; it does not resist a head of water pressing against it, and the pressure a saturated soil can generate is substantial. The coating is the last line — the drainage that keeps water from building up against the wall in the first place is what actually keeps the basement dry.

What is the difference between positive and negative side?

Which face the water is on. A positive-side coating is applied to the outside, where water arrives, and is pressed against the wall by the water. A negative-side coating is applied inside and is being pushed off the wall. They are different products with different adhesion and permeability requirements, and using one where the other belongs is a common and expensive substitution.

Why did my coating blister off?

Usually moisture behind it, or a substrate that was not prepared. A negative-side coating applied over a wall that is still passing water will be lifted off by that water; a coating applied over dust, laitance or a curing compound never bonded in the first place. Preparation is a larger share of the labour than the application.

Where does the water actually go?

That is the question that decides whether the system works. A perimeter drain must discharge somewhere — to daylight, to a storm connection, or to a sump with a pump — and a drain that discharges nowhere is a reservoir against the footing. Any waterproofing scheme that does not answer this question is incomplete regardless of what is on the wall.

Does the data sheet's rate mean per coat or for the whole system?

Data sheets give it both ways, and this page needs the per-coat rate, because it multiplies by the number of coats. The litres are wall area divided by the rate, times the number of coats, so the rate has to be what ONE coat covers: check which the sheet gives before entering it. Some data sheets give the rate for the finished system, the total thickness built up in two or three coats, and entering that rate with 2 coats buys the system twice. The metric page opens at 60 m² and 1 m²/L, which gives 60 L a coat and 120 L for two; the imperial page opens at 650 sq ft and 40 sq ft/gal, which gives 16.25 US gal a coat and 32.5 US gal for two. If the sheet's rate was already the two-coat total, the one-coat figure was the order. The opposite slip, a per-coat rate entered with 1 coat because the coat count is printed elsewhere on the sheet, halves the figure on the one element where a thin spot is the failure.

How is a specified thickness turned into a coverage rate?

Divide it into one. A wet film 1 mm (39 mils) thick uses a litre for every square metre, so 1 mm wet is 1 m²/L (about 41 sq ft/gal) and 2 mm (79 mils) wet is 0.5 m²/L (about 20 sq ft/gal); in US units, 1,604 divided by the wet thickness in mils gives square feet per gallon, so 40 mils wet is about 40 sq ft/gal. A specification can instead state a DRY film thickness, what is left on the wall once the water or solvent has gone, and this site's liquid waterproofing volume calculator converts that with the product's solids content. Worked here as if it were the wet figure, a dry thickness orders only the solids: at 60 per cent solids that is 40 per cent short, and only a product near 100 per cent solids has wet and dry figures that agree.

Is a foundation coating waterproofing or damp-proofing?

The codes treat them as different jobs, and a coating can be either. In the US, IRC Section R406 requires dampproofing on foundation walls that retain earth and enclose space below grade, and waterproofing instead where a high water table or other severe soil-water conditions are known; a thin asphalt coat that meets the first is not a substitute for the second, which calls for a coating or membrane of a type R406.2 lists. In the UK the same work is called tanking or waterproofing and is designed to BS 8102, which classes a coating on the outside as Type A (barrier) protection and settles the grade the space needs and the site's water conditions before a system is chosen. The litres here come out the same either way; the product, the coat count and the thickness are what that decision fixes, and it comes first.

How does the litre figure become an order?

For a coating sold by volume, divide it by the container and round up: the page's defaults, 120 L in metric or 32.5 US gal in imperial, both make seven pails of 5 US gal (18.9 L). Such a coating comes in pails or drums, and the metric default is six and a third of those pails and the imperial one six and a half, which either way means seven. How the product is sold changes the rest. A cementitious slurry, or a two-part coating with a powder component, can be sold by weight, and its data sheet then gives kilograms per square metre rather than square metres per litre; for those, the bag count comes from that figure and the area, and this page's litres are not the order unless the sheet also states a coverage per mixed litre. A two-part product also has a pot life, so the order has to divide into batches that can be applied before they stiffen, a loss the litre total cannot show.

Materials & Quantities

Basement Wall Waterproofing Coating Coverage Calculator

Calculate the waterproofing coating needed for a basement wall based on coverage rate and number of coats.

Answers as you typeNo submit button
Every formula citedNamed published standards
Calculated in your browserNo account, nothing uploaded

SettingsSettings for this calculationUS

Market

Imperial · sales tax

Wall Area

The total basement wall area to be coated.

Measure the total below-grade wall surface area that will receive the waterproofing coating.

Coverage Rate per Coat

The area one unit of coating covers in a single coat, per the manufacturer's data sheet.

Take this off the data sheet rather than from experience with paint: heavy-bodied foundation coatings are applied to a wet film thickness and cover far less than a wall finish. Rubberised asphalt and spray elastomerics run around 1 m²/L (roughly 40 sq ft/gal) and trowelled systems can be under half that, where a masonry paint is 5-10. Coverage also depends on the substrate — rougher or more porous block absorbs more material and reduces coverage further, and the rate on the sheet is usually quoted over a smooth surface.

Number of Coats

The total number of coats specified for the application.

Most waterproofing coatings require at least two coats to achieve a continuous, pinhole-free membrane — check the product's technical data sheet for its specific requirement.

Waterproofing coating needed

32.5 gal

Medium confidence

A coating on a basement wall is one part of a system whose other parts — drainage, a drainage board, and somewhere for water to go — do most of the work. Applied alone against real hydrostatic pressure, a coating is being asked to do something it cannot.

Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

Material needed = (area ÷ coverage rate per coat) × number of coats, the standard multi-coat coverage method

Inputs used

Wall Area: 650 sq ft
Coverage Rate per Coat: 40 ft²/gal
Number of Coats: 2

Final result32.5 gal

Confidence note: A coating on a basement wall is one part of a system whose other parts — drainage, a drainage board, and somewhere for water to go — do most of the work. Applied alone against real hydrostatic pressure, a coating is being asked to do something it cannot.

What this calculation does not cover

Excludes the drainage board, protection layer, perimeter drain and the sump or outfall the drain discharges to.
Coverage rates assume a sound, prepared substrate. A rough or porous wall consumes considerably more, and voids must be filled before coating rather than by it.
Positive-side and negative-side applications are different products for different situations; a coating designed to be applied externally will not necessarily work applied internally.

Estimated cost — your price

Price per gal ($)

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Part of bigger jobs

This trade is one line of several job takeoffs. Run the whole job and every other trade comes back with it, off the same measurements.

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Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.1.1

Regulatory standards & verification citations1

Material needed = (area ÷ coverage rate per coat) × number of coats, the standard multi-coat coverage method

Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Tools and safety for this job

To roll and cut in two coats and tank the walls and a basement's floor (waterproofing). Generic types, no brands, no prices.

Protection this work requires

Cutting or grinding concrete, masonry, screed, tile or fibre-cement board releases respirable silica: cut wet or extract at the tool, and wear a P2/N95 respirator at minimum — a nuisance dust mask does not filter it.
A dust mask does nothing about solvent vapour: ventilate through, and use an organic-vapour (A1) cartridge respirator in an enclosed room.
Wet cement and lime burn skin and eyes painlessly until the damage is done: waterproof gloves to EN 374, safety glasses whenever the mix can splash, and never kneel in wet mix in permeable trousers.
Saws, grinders and breakers run above 85 dB, where hearing damage accumulates and does not recover: defenders or plugs for every cut, not just the long ones.
Breakers and grinders cause permanent nerve damage: limit continuous trigger time, keep hands warm, and stop if fingers tingle or blanch.
Boards, blocks and bagged material cause most lasting back injuries on small sites: two people or a lifter for full sheets, and never a bag on one shoulder up a ladder.
Most fatal falls on small jobs are from under three metres: use a tower or a ladder tied at the top, and never work off the top two rungs.
Knives cause more site injuries than any power tool: cut away from your body, change blades often, and wear cut-resistant gloves to EN 388 level C for repeated cutting.

Tank the walls and a basement's floor (waterproofing): Applying a slurry or a coating to its maker's instructions is within reach of a competent builder. Which grade of dry space the basement needs (in the UK, BS 8102's grades 1 to 3), whether a barrier on its own will do or a drained cavity is needed with it, and how every joint, penetration and junction is detailed are the waterproofing designer's, and the standard asks for a waterproofing specialist in that design; this site flags the grade and never chooses it. A barrier on the inside face holds back water under pressure only where the wall behind it can carry that pressure, a structural question this site never sizes. On a wall that holds back no ground, where a damp specification names this protection, that specification sets which walls and how high, and the basement grade above does not apply.

Show the 10 tools this job needs

Essential

Brushes
Dust sheets and masking
Mixing bucket or tub
Paddle mixer
Roller frame, sleeves and tray
SDS rotary hammer

Recommended

Extension pole
Plastering trowel and hawk
Step ladder

Optional

Utility knife

Also needed as materials: masking tape, plastic sheeting, replacement blades, roller sleeves, SDS bits and chisels.

what each painting tool is for and what each waterproofing tool is for, and the spec that decides which to buy where one does.

Now that you have the number

These guides cover the work this quantity is for — the first ones run this calculator inside the section that raises the question.

Draining a Wet Basementuses this calculator
Wet basements are a pressure problem: read the head, relieve it at the slab and footing, and pump only what the relief path actually delivers.
Injecting a Remedial DPC and Replastering After Ituses this calculator
Hole spacing, cream volume per metre, what the drying wait is really for, and why the replaster over an injected course is a salt specification.
Laying a Patio Against the House Without Bridging the DPCuses this calculator
Two courses of brick between the ground and the damp course, and a back door that wants to be flush: the three ways that gets resolved.

Called something else where you work? Tanking and below-ground waterproofing — the term in each market, how close the equivalence really is, and the standard that governs it.

Still deciding? Tanking vs Drained Cavity — the factors that actually differ, with no invented prices.

Already have some? How much basement wall will my waterproofing coating cover?

The data behind it: Production rates by operation

How to calculate basement wall waterproofing coating coverage in 4 steps

Wall AreaThe total basement wall area to be coated.
Coverage Rate per CoatThe area one unit of coating covers in a single coat, per the manufacturer's data sheet.
Number of CoatsThe total number of coats specified for the application.
Waterproofing coating neededThe tool computes the waterproofing coating needed from those figures and shows the formula, its sources, and a confidence rating alongside it.

Waterproofing coating needed by wall area

Page defaults, not your figures above.

Wall Area	Waterproofing coating needed (gal)
400 sq ft	19.6
600 sq ft	29.5
800 sq ft	39.3
1,000 sq ft	49.1
1,200 sq ft	58.9

Frequently asked questions

Will a coating alone keep a basement dry?: Not against standing water. A coating resists moisture passing through the wall; it does not resist a head of water pressing against it, and the pressure a saturated soil can generate is substantial. The coating is the last line — the drainage that keeps water from building up against the wall in the first place is what actually keeps the basement dry.
What is the difference between positive and negative side?: Which face the water is on. A positive-side coating is applied to the outside, where water arrives, and is pressed against the wall by the water. A negative-side coating is applied inside and is being pushed off the wall. They are different products with different adhesion and permeability requirements, and using one where the other belongs is a common and expensive substitution.
Why did my coating blister off?: Usually moisture behind it, or a substrate that was not prepared. A negative-side coating applied over a wall that is still passing water will be lifted off by that water; a coating applied over dust, laitance or a curing compound never bonded in the first place. Preparation is a larger share of the labour than the application.
Where does the water actually go?: That is the question that decides whether the system works. A perimeter drain must discharge somewhere — to daylight, to a storm connection, or to a sump with a pump — and a drain that discharges nowhere is a reservoir against the footing. Any waterproofing scheme that does not answer this question is incomplete regardless of what is on the wall.
Does the data sheet's rate mean per coat or for the whole system?: Data sheets give it both ways, and this page needs the per-coat rate, because it multiplies by the number of coats. The litres are wall area divided by the rate, times the number of coats, so the rate has to be what ONE coat covers: check which the sheet gives before entering it. Some data sheets give the rate for the finished system, the total thickness built up in two or three coats, and entering that rate with 2 coats buys the system twice. The metric page opens at 60 m² and 1 m²/L, which gives 60 L a coat and 120 L for two; the imperial page opens at 650 sq ft and 40 sq ft/gal, which gives 16.25 US gal a coat and 32.5 US gal for two. If the sheet's rate was already the two-coat total, the one-coat figure was the order. The opposite slip, a per-coat rate entered with 1 coat because the coat count is printed elsewhere on the sheet, halves the figure on the one element where a thin spot is the failure.
How is a specified thickness turned into a coverage rate?: Divide it into one. A wet film 1 mm (39 mils) thick uses a litre for every square metre, so 1 mm wet is 1 m²/L (about 41 sq ft/gal) and 2 mm (79 mils) wet is 0.5 m²/L (about 20 sq ft/gal); in US units, 1,604 divided by the wet thickness in mils gives square feet per gallon, so 40 mils wet is about 40 sq ft/gal. A specification can instead state a DRY film thickness, what is left on the wall once the water or solvent has gone, and this site's liquid waterproofing volume calculator converts that with the product's solids content. Worked here as if it were the wet figure, a dry thickness orders only the solids: at 60 per cent solids that is 40 per cent short, and only a product near 100 per cent solids has wet and dry figures that agree.
Is a foundation coating waterproofing or damp-proofing?: The codes treat them as different jobs, and a coating can be either. In the US, IRC Section R406 requires dampproofing on foundation walls that retain earth and enclose space below grade, and waterproofing instead where a high water table or other severe soil-water conditions are known; a thin asphalt coat that meets the first is not a substitute for the second, which calls for a coating or membrane of a type R406.2 lists. In the UK the same work is called tanking or waterproofing and is designed to BS 8102, which classes a coating on the outside as Type A (barrier) protection and settles the grade the space needs and the site's water conditions before a system is chosen. The litres here come out the same either way; the product, the coat count and the thickness are what that decision fixes, and it comes first.
How does the litre figure become an order?: For a coating sold by volume, divide it by the container and round up: the page's defaults, 120 L in metric or 32.5 US gal in imperial, both make seven pails of 5 US gal (18.9 L). Such a coating comes in pails or drums, and the metric default is six and a third of those pails and the imperial one six and a half, which either way means seven. How the product is sold changes the rest. A cementitious slurry, or a two-part coating with a powder component, can be sold by weight, and its data sheet then gives kilograms per square metre rather than square metres per litre; for those, the bag count comes from that figure and the area, and this page's litres are not the order unless the sheet also states a coverage per mixed litre. A two-part product also has a pot life, so the order has to divide into batches that can be applied before they stiffen, a loss the litre total cannot show.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.