How Much Waterproofing Membrane for a Shower?
Tile and grout do not stop water, so a shower needs a waterproof layer behind them. A 5 × 3 ft alcove shower waterproofed 6 ft high has 81 ft² to cover (15 ft² of floor and 66 ft² of wall). That is 2 rolls of 54 ft² sheet membrane or 2 gallons of liquid at 55 ft² per gallon, with 10% extra, and 26 ft of band for the corners. The shower waterproofing calculator does it for your shower.
Part of the project planner: Planning new floors and tile.
Sheet or liquid
Sheet membrane (such as Schluter KERDI) comes in rolls 3 ft 3 in wide, bonded to the wall with thinset, and seams are lapped 2 inches or butted and covered with a band. Liquid membrane (such as RedGard) is rolled or troweled on in two coats and covers about 55 ft² per gallon. Both need a band or fabric at the corners and the drain. Pick one system and use its fittings, as the two are alternatives, not a pair.
Quantities by shower size
Alcove shower, walls waterproofed 6 ft high, 10% extra, 54 ft² rolls:
| Shower | Area | Rolls | Liquid | Band |
|---|---|---|---|---|
| 3 × 3 ft | 63 ft² | 2 | 2 gal | 24 ft |
| 4 × 3 ft | 72 ft² | 2 | 2 gal | 25 ft |
| 5 × 3 ft | 81 ft² | 2 | 2 gal | 26 ft |
| 6 × 3 ft | 90 ft² | 2 | 2 gal | 27 ft |
| 5 × 4 ft | 98 ft² | 3 | 2 gal | 28 ft |
Quantities by wall height
For a 5 × 3 ft alcove:
| Height | Area | Rolls | Liquid |
|---|---|---|---|
| 5 ft | 70 ft² | 2 | 2 gal |
| 6 ft | 81 ft² | 2 | 2 gal |
| 7 ft | 92 ft² | 2 | 2 gal |
| 8 ft | 103 ft² | 3 | 3 gal |
| 9 ft | 114 ft² | 3 | 3 gal |
Getting it right
- Waterproof the walls as well as the floor of the shower: water passes through grout.
- Seal the floor-to-wall joint, every inside corner and the drain with the band, fabric or fittings of the same system.
- Add the niche, the bench and the curb separately: they need their own pieces.
- Apply liquid in two even coats at the thickness on the label, and let the first dry before the second.
- Flood-test a shower floor for 24 hours before you tile.
Plan the tile with the tile layout calculator and count it with the tile calculator. Local codes and the maker's instructions rule over any figure here.
Frequently asked questions
How much waterproofing do I need for a shower?
Add the floor and the walls. A 5 × 3 ft alcove shower waterproofed 6 ft high is 81 ft², which takes 2 rolls of 54 ft² sheet membrane or 2 gallons of liquid, with 10% extra.
How high does shower waterproofing go?
The IRC asks for a nonabsorbent finish on shower walls to at least 6 feet above the floor. Many installers go to the ceiling. The membrane maker's instructions say what they need.
How much does a gallon of liquid membrane cover?
RedGard is rated at 55 ft² per gallon for waterproofing, in two coats. Other products differ, so use the label.
Do I waterproof the walls and the floor?
Yes, in the shower itself. Tile and grout let water through, so the membrane behind them is the waterproofing.
More guides
Tools & materials for this project
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Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and follow local building codes for anything structural.
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