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Mapelastic AquaDefense Coverage Calculator: How Many Gallons?

Enter the area you want to waterproof and the calculator applies the coverage MAPEI prints in its US data sheet MK 3002103 (edition date June 9, 2025): two coats, with one gallon finishing about 60 sq ft. It then picks the 1, 3.5 and 5 gallon pails to buy. A second setting works from the wet film thickness in the same data sheet, which uses more liquid, if you want a safety margin.

MAPEI Mapelastic AquaDefense coverage

Source: MAPEI Technical Data Sheet: Mapelastic AquaDefense (US, English), MK 3002103 (25-1788), Edition Date June 9, 2025, read 2026-10-17.

How the calculation works

gallons = area × (1 + waste ÷ 100) × coats ÷ sq ft per gallon per coat

Every coat goes over the whole area, so two coats at 80 sq ft per gallon use as much liquid as one coat at 40. The rate depends on what the membrane is for: the data sheet lists a heavier rate for code-listed waterproofing than for crack prevention alone. The calculator then picks the fewest pails that cover the job without leaving more than one small pail of liquid unused, so a job needing 3 gallons gets one 3.5 gallon pail rather than three 1 gallon pails. Extra passes over corners, seams, drains and pipe penetrations are not included; raise the waste figure if you have many of them.

Worked example

A 100 sq ft area, Coverage chart: 2 coats, 60 sq ft per gallon finished, with 10% extra: 100 × 1.1 = 110 sq ft. The data sheet calls for 2 coats at 120 sq ft per gallon each, so 110 × 2 ÷ 120 = 1.83 gallons (6.9 L). In the pail sizes on sale, buy 2 × 1 gal pails (2 gal).

MAPEI Mapelastic AquaDefense key specs

What Mapelastic AquaDefense is

Mapelastic AquaDefense from MAPEI is a premixed liquid rubber membrane that you roll or brush onto the substrate before setting ceramic tile or stone. It dries very quickly to a thin, continuous film that works as both a waterproofing membrane and a crack isolation membrane. It goes on light bluish green and dries to a light green, which is how you tell when the next coat can go on; MAPEI lightened the color a few years ago so chalk layout lines show up better on the dried membrane.

MAPEI's US data sheet MK 3002103 lists it for residential and commercial interior and exterior floors, walls and ceilings, industrial interior floors and walls, tub and shower surrounds, kitchens, laundries and food preparation areas, countertops, freshwater pools and fountains fully covered by tile, balconies over unoccupied space, and steam rooms and steam showers. It exceeds ANSI A118.10-LV for waterproofing and ANSI A118.12 for crack isolation, is IAPMO listed as a shower-pan liner (File 3996), has an ICC-ES report (ESR 3474) and an "Extra Heavy" rating from the ASTM C627 Robinson floor test. Its vapor permeance is 0.35 perms, low enough for steam showers, which is something not every liquid membrane can claim.

What the data sheet says about coverage

The packaging table in MK 3002103 gives coverage per two coats for each container: 60 sq ft (5.57 m²) for the 1 gallon pail, 210 sq ft (19.5 m²) for the 3.5 gallon pail, 300 sq ft (27.9 m²) for the 5 gallon pail and 3,300 sq ft (307 m²) for the special order 55 gallon drum. Every one of those works out to the same 60 sq ft per gallon, so the calculator's default setting uses two coats at 120 sq ft per gallon each. The data sheet adds that the figures are for estimating only and that real coverage depends on the substrate, its profile and porosity, the tools and the thickness you apply.

The same data sheet also sets a wet film thickness: 20 mils for the first coat and 15 mils for the second, with a final dry thickness of about 20 mils at minimum, roughly the thickness of a credit card. Those numbers do not quite match the coverage table. A US gallon is 231 cubic inches, and spread 35 mils (0.035 inch) thick in total it covers about 46 sq ft, not 60. The usual explanation is that the table assumes a thinner real-world film than the target wet thickness, but the data sheet does not say which figure wins. So the calculator offers a second setting, two coats at 91 sq ft per gallon, that follows the full wet film. Use it if you check your coats with a wet film gauge and roll them on to the stated thickness, or simply if you want a margin.

How the calculator works

Enter the area and a waste allowance. The calculator multiplies the area with waste by two coats and divides by the per-coat rate you picked, which gives the gallons of AquaDefense you need. It then chooses pails from the three sizes MAPEI sells: the fewest pails that hold enough, as long as you are not left with more than one 1 gallon pail's worth unused. A job needing 1.8 gallons gets two 1 gallon pails, a job needing 3.2 gallons gets one 3.5 gallon pail, and a job needing 4.6 gallons gets one 5 gallon pail. Prices change by store, so they are not part of the rule; once you are past about 3 gallons, compare a large pail against several small ones where you shop.

The result does not include pre-treatment. Before the main coats MAPEI asks for two coats, 6 inches on each side, over cracks, corners and coves, two coats over and around the drain flange, and two coats around pipe penetrations. For crack isolation over a single crack, the band is 6 inches on each side plus three times the width of the largest tile. On a plain shower this is a small amount; with a bench, a niche and several valves, raise the waste figure to 15 or 20 percent.

Measuring a shower or floor

Measure every surface that gets membrane, not just the floor: the three walls of an alcove up to the height you waterproof, the top and both faces of the curb, and every face of a niche or bench. A 3 x 5 ft shower with walls coated to 7 ft is 15 sq ft of floor and 77 sq ft of wall, 92 sq ft before waste. With 10 percent extra and the default rate that is about 1.7 gallons, so two 1 gallon pails; on the wet film setting it is about 2.2 gallons, so three. On a floor, measure the room and add a strip up the walls if you turn the membrane up at the perimeter.

Application notes from the data sheet

Substrates must be sound, stable, dry and clean. Concrete should be cured at least 28 days and have an ICRI surface profile of CSP 2; do not prepare it with acid etching or strippers. Moisture emission must not exceed 8 lb per 1,000 sq ft per 24 hours or 85 percent relative humidity. Substrate and room must stay between 45°F and 95°F during application and for 24 hours after. Fill cracks, joints and gaps wider than 1/32 inch first. Mix the pail by hand and never dilute it.

Roll the main area with a 3/8 inch nap roller, let the first coat turn light green and dry to the touch, then apply the second coat over everything. Inspect for pinholes and thin spots and recoat them. MAPEI's optional Reinforcing Fabric or Mapeband cove roll and drain flashing can be embedded in the wet first coat, but fabric is not required. Tile can follow about 30 to 50 minutes after the second coat with a polymer-modified mortar to ANSI A118.4, A118.11 or A118.15 or an epoxy to A118.3; do not use mastic or premixed adhesives over the membrane. Cover it with tile within 72 hours if you can, and never leave it exposed more than 7 days.

Check before you buy

The numbers on this page come from MAPEI Technical Data Sheet MK 3002103 (25-1788), edition date June 9, 2025, the US English version on MAPEI's document server. If your estimate lands right at a pail boundary, round up: running short between the first and second coat leaves the job waiting while you go back to the store.

FAQ

How many square feet does a gallon of Mapelastic AquaDefense cover?

About 60 sq ft with the two coats MAPEI requires. The packaging table in data sheet MK 3002103 lists the 1 gallon pail at 60 sq ft, the 3.5 gallon pail at 210 sq ft and the 5 gallon pail at 300 sq ft, all per 2 coats, and notes that jobsite coverage varies with the substrate, its profile and porosity, the tools and the thickness applied.

How much AquaDefense do I need for a shower?

Add the floor, every wall surface you will waterproof, the curb and any niche or bench. A 3 x 5 ft alcove shower with three walls coated to 7 ft is 15 sq ft of floor plus (5 + 3 + 3) x 7 = 77 sq ft of wall, 92 sq ft in total. With 10 percent extra that is about 101 sq ft, which at 60 sq ft per gallon is about 1.7 gallons, so two 1 gallon pails. The two pre-treatment coats over corners, coves and the drain come on top, so if your shower has a bench or niche, buy a third gallon or a 3.5 gallon pail.

Why does the calculator have a second, heavier setting?

The data sheet gives two figures that do not quite agree. Its coverage table works out to 60 sq ft per gallon for both coats. Its application table asks for a wet film of 20 mils on the first coat and 15 mils on the second, 35 mils in all, and a US gallon (231 cubic inches) spread 35 mils thick covers about 46 sq ft. If you roll on the full wet film, plan on the heavier setting. Either way, MAPEI's minimum is about 20 mils of dry membrane after both coats.

Is the 1 gallon 4-pack 60 sq ft or 240 sq ft?

The data sheet lists the 1 gallon pail as a 4-pack with 60 sq ft of coverage. Since the 3.5 and 5 gallon pails are listed at exactly 60 sq ft per gallon too, the 60 sq ft is per 1 gallon pail, so a full 4-pack covers about 240 sq ft. The calculator counts single 1 gallon pails; if your store only sells the 4-pack, round up to whole packs.

How long before I can tile or flood test?

At 73°F and 50 percent relative humidity, tile can go on about 30 to 50 minutes after the second coat, once it is light green and dry to the touch. Wait at least 8 hours before using large-and-heavy-tile mortars, screeds or epoxy adhesives, and at least 12 hours before a flood test to ASTM D5957. Cooler weather takes longer. MAPEI recommends tiling within 72 hours and no more than 7 days of exposure.

MAPEI and MAPEI Mapelastic AquaDefense are trademarks of their owner. This page is an independent estimate based on the published data sheet; check the bag label before mixing.