Waterproofing Membrane Calculator
Enter the room length and width and the wall upstand height to calculate the total waterproofing membrane area (including the perimeter turn-up) for bathroom, kitchen and balcony waterproofing takeoff and pricing.
Input Data
Results
At a glance:Total membrane area = floor area + four-side upstand area. Floor = length × width; upstand = 2×(length+width) × upstand height (mm) ÷ 1000. Total area × (1 + waste%) gives the purchasing area. Hong Kong bathroom waterproofing commonly requires the floor to turn continuously up the wall at least 100 mm, higher in shower areas; the threshold must be sealed. Liquid waterproofing is estimated by membrane area × product rate (usually 1.5–2.0 kg/m² for two coats).
Formula
Floor = length × width
Upstand = 2(length+width) × upstand/1000
Total = (floor + upstand) × (1+waste%)
$$A_g = L W$$$$A_u = 2(L+W)\frac{h}{1000}$$$$A_t = (A_g + A_u)(1+w)$$How to Use
- Enter the room length and width.
- Enter the wall upstand height (mm).
- Set the waste.
- The tool outputs the total membrane area.
Case Studies
Bathroom waterproofing
3×2 m, upstand 150 mm, waste 10%.
Floor 6 m²; upstand 1.5 m²; total 8.25 m² (9.08 m² with waste).
Balcony waterproofing
5×4 m, upstand 200 mm, waste 10%.
Floor 20 m²; upstand 3.6 m²; total 25.96 m².
FAQ
Why is the upstand important?
The wall–floor junction is a high leak-risk point; turning the membrane continuously up the wall forms a continuous barrier and avoids joint leakage.
How to estimate liquid waterproofing?
Multiply the membrane area by the product rate per m² (usually 1.5–2.0 kg/m² for two coats) to get the total weight.
Related Tools
References
Content review: Calculatorism Construction Team. Results are for reference only; please refer to the relevant authorities for the official figures.