Cold-Applied Liquid Waterproofing Membrane Volume Calculator

SettingsSettings for this calculationUS

Market

Imperial · sales tax

Area to Waterproof

The total surface area to be waterproofed.

Measure the full surface area receiving the liquid-applied membrane.

Target Dry Film Thickness (mils)

The cured (dry) membrane thickness required by the manufacturer's spec.

This is the final, cured thickness the waterproofing system needs to perform — check the product's technical data sheet for the minimum required dry film thickness.

Product Solids Content (%)

The percentage of the wet product that remains after solvent/water evaporates during cure.

A lower solids content means more wet material must be applied to achieve the same dry film thickness, since more volume is lost to evaporation.

Liquid membrane volume needed

25.2 gal

Medium confidence

Solids content and dry film thickness requirements vary by manufacturer and application (horizontal vs. vertical, exposure condition) — confirm your specific product's technical data sheet for exact coverage rates.

Required wet film thickness: 75 mils

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

Show calculation logic

How this was calculated

Formula source(s)

Wet film thickness = target dry film thickness ÷ solids content fraction, since liquid-applied membranes lose volume as solvent/water evaporates during cure; material volume = area × wet film thickness

Inputs used

Area to Waterproof: 540 sq ft
Target Dry Film Thickness (mils): 60
Product Solids Content (%): 80

Intermediate steps

Required wet film thickness: 75 mils

Final result25.25 gal

Confidence note: Solids content and dry film thickness requirements vary by manufacturer and application (horizontal vs. vertical, exposure condition) — confirm your specific product's technical data sheet for exact coverage rates.

What this calculation does not cover

A cold-applied system is resin plus reinforcement, and the reinforcement drinks far more than the field coat does. Polyester fleece has to be wetted out from underneath and above to be properly embedded, and every upstand, internal corner, outlet, penetration and movement joint takes a reinforced detail band laid before the field goes down. Detailing consumes material at a rate that has nothing to do with the flat area, and it is where jobs run short.
The area entered is a flat surface, and a waterproofed roof is not one. Upstands of 150 mm (6 in) and more right round the perimeter, kerbs to every rooflight and plant base, gutter cheeks and the flange of every outlet are all additional surface, and on a small busy roof that detail area can rival the field it surrounds.

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 · v1.0.1

Regulatory standards & verification citations1

Wet film thickness = target dry film thickness ÷ solids content fraction, since liquid-applied membranes lose volume as solvent/water evaporates during cure; material volume = area × wet film thickness

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 apply a liquid waterproofing membrane. Generic types, no brands, no prices.

Protection this work requires

A dust mask does nothing about solvent vapour: ventilate through, and use an organic-vapour (A1) cartridge respirator in an enclosed room.
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.

Show the 5 tools this job needs

Essential

Brushes
Roller frame, sleeves and tray

Recommended

Mixing bucket or tub
Paddle mixer
Utility knife

Also needed as materials: replacement blades, roller sleeves.

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.

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The doorway is the one junction on a building where a wet outdoor floor meets a dry indoor one at the same level. Detail it outward from there.

Falls, Tanking and the Gully in a Wet Room Flooruses this calculator

A walk-in shower cut into a floor that already exists: the depth budget under it, the gradient band the codes barely leave open, and the tanking above it.

Tiling a Commercial Kitchen Flooruses this calculator

Quarry tile priced the way a kitchen fails it: falls to the gullies, ten-millimetre joints in chemical-resistant grout, a trim on every edge that stops.

How to calculate cold-applied liquid waterproofing membrane volume in 4 steps

Area to WaterproofThe total surface area to be waterproofed.

Target Dry Film Thickness (mils)The cured (dry) membrane thickness required by the manufacturer's spec.

Product Solids Content (%)The percentage of the wet product that remains after solvent/water evaporates during cure.

Liquid membrane volume neededThe tool computes the liquid membrane volume needed from those figures and shows the formula, its sources, and a confidence rating alongside it.

Area to Waterproof	Liquid membrane volume needed (gal)
400 sq ft	18.7
600 sq ft	28.1
800 sq ft	37.4
1,000 sq ft	46.8

Area to Waterproof

Liquid membrane volume needed (gal)

400 sq ft

18.7

600 sq ft

28.1

800 sq ft

37.4

1,000 sq ft

46.8

Frequently asked questions

Why is the required wet film thickness greater than the dry film thickness?

Liquid-applied membranes lose volume as solvent or water evaporates during cure. Since the product isn't 100% solids, you must apply more material wet than the cured thickness that remains — wet film thickness = target dry film thickness ÷ solids content fraction.

Where do I find my product's solids content?

It's listed on the manufacturer's technical data sheet, usually as a percentage by volume. Use that exact figure rather than an assumed value, since it directly changes how much material you need to order.

Does required dry film thickness change between horizontal and vertical applications?

Yes — manufacturers often specify different minimum dry film thicknesses depending on whether the membrane is applied horizontally or vertically, and on the exposure/hydrostatic condition. Always confirm the correct target DFT for your specific application from the product's data sheet.