Home › Waterproofing membrane › MAPEI Mapelastic CI
Mapelastic CI Coverage Calculator: How Many Gallons?
Enter the floor area you want to protect from cracks and the calculator applies the coverage MAPEI prints in its US data sheet MK 3000137 (edition date October 1, 2024): one coat rolled on at 20 mils wet, drying to at least 15 mils, with one gallon covering about 71 sq ft. It then picks the 1 and 3.5 gallon pails to buy. A second setting doubles the liquid for jobs where you expect to roll a full second coat.
MAPEI Mapelastic CI coverage
| Application | Coats | Per gallon, each coat | Per gallon, all coats |
|---|---|---|---|
| Coverage chart: 1 coat, 15 mils dry (71 sq ft per gallon) | 1 | 71 sq ft (6.6 m²) | 71 sq ft (6.6 m²) |
| Two full coats (if the first coat leaves thin spots everywhere) | 2 | 71 sq ft (6.6 m²) | 35.5 sq ft (3.3 m²) |
Source: MAPEI Technical Data Sheet: Mapelastic CI (US, English), MK 3000137 (24-2216), Edition Date October 1, 2024, read 2026-10-19.
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 300 sq ft area, Coverage chart: 1 coat, 15 mils dry (71 sq ft per gallon), with 10% extra: 300 × 1.1 = 330 sq ft. The data sheet calls for 1 coat at 71 sq ft per gallon each, so 330 × 1 ÷ 71 = 4.65 gallons (17.6 L). In the pail sizes on sale, buy 1 × 3.5 gal pail + 2 × 1 gal pails (5.5 gal).
MAPEI Mapelastic CI key specs
| Product type | Waterproofing membrane |
|---|---|
| Package | 1 gal (3.79 L) and 3.5 gal (13.2 L) pails |
| Coverage (data sheet, 15 mils dry) | 1 gal (3.79 L) pail: 71 sq ft (6.60 m²); 3.5 gal (13.2 L) pail: 250 sq ft (23.2 m²) |
| Film thickness | one coat at 20 mils wet with a 3/8 in (10 mm) nap roller; at least 15 mils dry; second coat at right angles only where the first did not cover properly |
| Drying | ready for tile mortar in about 30–50 minutes, when dry to the touch and dark brown; protect from foot traffic, rain and freezing for 24 hours (73°F, 50% RH) |
| Color | purple when wet, dark brown when dry |
| Crack isolation | in-plane, nonstructural floor cracks up to 1/8 in (3 mm); not over structural cracks or where vertical movement occurs |
| Standards | meets ANSI A118.12 (crack isolation); ASTM C627 "Extra Heavy" service rating; not listed as a waterproofing membrane (no A118.10) |
| Temperature | substrate and room 45–95°F (7–35°C) during application and for at least 24 hours after |
| Not for | structural cracks, hardwood, OSB, metal, plank flooring, treated plywood, lauan, vinyl, glazed tile, laminate, fiberglass or epoxy floors, premixed setting materials, extreme freeze/thaw, slabs over 8 lb MVER or 85% RH |
| Shelf life | 2 years in unopened containers at 73°F (23°C); protect from freezing |
What Mapelastic CI is
Mapelastic CI from MAPEI is a premixed, liquid rubber membrane that you roll onto a floor before setting ceramic tile or stone. Its job is crack isolation: it forms a thin, elastic film between the slab and the tile so that small in-plane cracks in the concrete do not travel up through the mortar, the tile and the grout. It goes on purple and dries to a dark brown, which is the signal that you can start setting tile, usually within 30 to 50 minutes.
MAPEI's US data sheet MK 3000137 lists it for residential and commercial floors, inside and outside, over nonstructural cracks up to 1/8 inch (3 mm) wide. It meets ANSI A118.12, the standard for crack-isolation membranes under thin-set tile, and carries an "Extra Heavy" rating from the ASTM C627 Robinson floor test, so it can go under tile in busy commercial areas. It has no odor and is ready to use straight from the pail after a stir by hand.
What the data sheet says about coverage
The packaging table in MK 3000137 gives coverage at a dry film thickness of 15 mils: 71 sq ft (6.60 m²) for the 1 gallon (3.79 L) pail and 250 sq ft (23.2 m²) for the 3.5 gallon (13.2 L) pail. The large pail works out to about 71.4 sq ft per gallon, so the two sizes are effectively the same rate and the calculator uses 71 sq ft per gallon for both. The data sheet adds that the figures are for estimating only and that real coverage depends on the substrate, its profile and porosity, the equipment and the thickness you apply.
The application section explains where that number comes from. You roll the whole area once at a wet film of 20 mils, about the thickness of a credit card, using a 3/8 inch (10 mm) nap roller. When it dries the film should be at least 15 mils, about a business card. A quick check: a US gallon is 231 cubic inches, and spread 20 mils (0.020 inch) thick it covers 231 ÷ 0.020 ÷ 144, or about 80 sq ft. The table's 71 sq ft is a little more conservative than that, which leaves room for porous concrete soaking some of it up and for the roller laying down slightly more than the target.
How the calculator works
Enter the floor area in square feet or square meters and a waste allowance. The calculator multiplies the area by one plus the waste, multiplies by the number of coats, and divides by 71 sq ft per gallon. It then picks pails: the fewest containers that cover the job without leaving more than one small pail of liquid unused. A 200 sq ft room with 10 percent extra needs 220 ÷ 71, or about 3.1 gallons, which is one 3.5 gallon pail rather than four single gallons.
The default setting is the single coat the data sheet calls for. The second setting doubles the liquid for a full second coat. MAPEI only asks for a second coat, rolled at right angles to the first, over spots the first coat did not cover properly, so most jobs land somewhere between the two figures. If the slab is rough or very absorbent, or you have not rolled a membrane before, raise the waste figure or use the two-coat setting to be safe.
Where it can and cannot go
The data sheet approves concrete cured at least 28 days, cured cement mortar beds and leveling coats, cement backer units, radiant-heated floors (interior only), unglazed ceramic tile and cement terrazzo once they have been abraded or profiled and skim-coated, gypsum underlayments over 2,500 psi (interior only), and exterior-grade plywood for interior residential floors and countertops in dry areas. Concrete should have a surface profile of CSP 2, and any crack or gap wider than 1/32 inch must be filled first.
It is not for structural cracks, cracks wider than 1/8 inch or anywhere the two sides of a crack move up and down relative to each other. It cannot go over hardwood, OSB, metal, plank flooring, treated plywood, lauan, vinyl, glazed tile, laminate, fiberglass or epoxy floors, or slabs with more than 8 lb of moisture vapor emission per 1,000 sq ft per 24 hours or 85 percent relative humidity. Keep the substrate and air between 45 and 95°F (7 and 35°C) during application and for at least a day after, and do not apply it when the slab is at or below the dew point.
Mapelastic CI versus Mapelastic AquaDefense
The two MAPEI membranes look similar in the pail but do different jobs. Mapelastic CI is a crack-isolation membrane only. Mapelastic AquaDefense meets ANSI A118.10 for waterproofing as well as A118.12, is listed for shower pans and steam showers, and needs two coats, so it covers about 60 sq ft per gallon finished instead of 71. If you are tiling a shower, a tub surround or a balcony over living space, use a waterproofing membrane. If you are tiling a kitchen, hallway or retail floor over a slab with shrinkage cracks, Mapelastic CI is the lighter, faster option.
After the membrane
Protect the dried membrane from foot traffic, rain and freezing for 24 hours, and from dirt, excessive heat and long sun exposure until the tile is down. Set tile with a MAPEI polymer-modified mortar that meets ANSI A118.4 and A118.11 (ISO 13007 C2) or an epoxy mortar meeting ANSI A118.3; premixed adhesives are not allowed. Large-and-heavy-tile mortars and leveling screeds may take longer to set on top of it. Keep expansion and control joints open per TCNA EJ171 and do not bridge structural expansion joints with the membrane or the mortar. Unopened pails keep for two years at room temperature as long as they never freeze.
FAQ
How many square feet does a gallon of Mapelastic CI cover?
About 71 sq ft at the 15 mil dry film MAPEI asks for. The packaging table in data sheet MK 3000137 lists the 1 gallon pail at 71 sq ft (6.60 m²) and the 3.5 gallon pail at 250 sq ft (23.2 m²), and notes that jobsite coverage varies with the substrate, the concrete profile and porosity, the equipment and the thickness applied.
What does a 3.5 gallon pail of Mapelastic CI cover?
250 sq ft, according to the data sheet. That is about 71.4 sq ft per gallon, so in practice the big pail and four 1 gallon pails go about the same distance (250 versus 284 sq ft). The calculator uses 71 sq ft per gallon for both sizes and picks the pail mix with the fewest containers that does not leave more than one small pail of liquid unused.
Does Mapelastic CI need two coats?
No. Unlike MAPEI's waterproofing membranes, the data sheet calls for a single coat at 20 mils wet with a 3/8 in nap roller, drying to at least 15 mils. You only add a second coat, rolled at right angles to the first, over areas that were not properly covered. If you are new to rolling membranes or the slab is very porous, the two-coat setting gives you the worst case.
Can I use Mapelastic CI to waterproof a shower?
Not according to the data sheet. Mapelastic CI meets ANSI A118.12 for crack isolation only; it does not claim ANSI A118.10 waterproofing or a shower-pan listing. For showers, MAPEI sells Mapelastic AquaDefense, whose data sheet lists both A118.10 waterproofing and A118.12 crack isolation. Use Mapelastic CI on interior or exterior floors where the goal is to stop slab cracks up to 1/8 in from telegraphing into tile and grout.
How soon can I set tile over it?
At 73°F and 50 percent relative humidity, about 30 to 50 minutes after rolling, once it is dry to the touch and has turned from purple to dark brown. Large-and-heavy-tile mortars and screeds may need longer to set over it. Set tile with a MAPEI polymer-modified mortar meeting ANSI A118.4 and A118.11 (ISO 13007 C2) or an epoxy mortar meeting A118.3, not with a premixed adhesive.
MAPEI and MAPEI Mapelastic CI are trademarks of their owner. This page is an independent estimate based on the published data sheet; check the bag label before mixing.