Overview
This calculator estimates liquid membrane, sealing compound, or similar waterproofing products for flat surfaces and damp-prone areas. It accounts for the number of coats, product coverage, waste allowance, and pack size so you can see both the required quantity and how many containers to buy. Use it when planning work around tiled wet rooms, exterior slabs, or below-grade concrete where stopping moisture matters. The result is a material estimate, not a substitute for the product data sheet or site-specific specification, so always compare it with the manufacturer’s stated consumption and the details of corners, joints, and penetrations.
Use cases
- Bathroom under tileEstimate membrane for a shower room floor and the lower part of the walls before tiling.
- Balcony edge protectionPlan the amount needed for a small balcony with extra losses at the drain and perimeter edges.
- Foundation damp proofingCheck how much coating is required for vertical foundation walls before backfilling.
- Repair zone around pipesSize material for a localized waterproofing repair around pipe penetrations and corners.
How it works
- 1
Enter the surface area to be covered.
- 2
Select how many coats the system requires.
- 3
Use the product coverage to calculate base quantity.
- 4
Add waste, then convert the total into packs and round up.
Examples
Small shower room floor
Input: 8.5 m², 2 coats, 1.2 m²/kg coverage, 12% waste, 5 kg pack
Output: Base: 14.2 kg; total: 15.9 kg; packs: 4.
A realistic estimate for a compact bathroom floor with two coats.
Roof terrace section
Input: 31 m², 3 coats, 0.75 m²/l coverage, 10% waste, 10 l pack
Output: Base: 124.0 l; total: 136.4 l; packs: 14.
Useful for a terrace section that needs a heavier waterproofing build-up.
Foundation wall run
Input: 18 m², 2 coats, 1.5 m²/kg coverage, 8% waste, 20 kg pack
Output: Base: 24.0 kg; total: 25.9 kg; packs: 2.
Good for a straight foundation wall area with modest losses.
FAQ
Does the result include corners, overlaps, and pipe collars?
Only if you include them in the area or add extra waste. Tight details often consume more material than flat fields.
What coverage value should I use?
Use the manufacturer’s coverage for the exact product and application method. Brush, roller, and trowel applications can differ.
Why does the pack count seem high?
The calculator rounds up to full packs, so a small remainder can push the result to the next container.
Can I use litres and kilograms interchangeably?
Only if the product density makes that acceptable. The tool follows the unit you enter, but the package label may use a different unit.
What is the most common mistake when entering the area?
Forgetting that walls, upstands, and edge strips are separate surfaces. If they are not part of the measured field, add them separately.