Waterproofing Calculator
Membrane area, rolls, primer and litres of liquid waterproofing, including the upstand at the walls.
Results
Total area to treat
14.100
m²
Flat area on the ground
12.000
m²
Area of that upstand
2.100
m²
Membrane to buy
15.792
m²
Rolls to buy
2
Liquid to buy, all coats
21.150
L
Primer to buy
2.820
L
Perimeter of the surface
14.000
m
Per coat
10.575
L
What this tool does
The part people forget is the upstand — waterproofing that stops at floor level stops working the moment water reaches the wall. This page adds the upstand to the flat area before it counts anything, and it separates the membrane area from the area to treat, because the overlap between sheets is material you buy and never see.
Formula
area to treat = area + perimeter × upstand height · membrane = area to treat × (1 + overlap) · litres = area to treat × consumption × coats
Variables
| Symbol | Meaning | Unit |
|---|---|---|
len | Length of the surface | m |
wid | Width of the surface | m |
up | How far it goes up the wall | m |
ov | Allowance for overlaps | % |
rl | Area of one roll | m² |
cn | Litres per square metre per coat | L/m² |
co | How many coats | — |
pr | Primer per square metre | L/m² |
TA | Total area to treat | m² |
FA | Flat area on the ground | m² |
UA | Area of that upstand | m² |
MA | Membrane to buy | m² |
NR | Rolls to buy | — |
LT | Liquid to buy, all coats | L |
PL | Primer to buy | L |
PE | Perimeter of the surface | m |
PC | Per coat | L |
Worked example
- Length of the surface4 m
- Width of the surface3 m
- How far it goes up the wall0.15 m
- Allowance for overlaps12 %
- Area of one roll10 m²
- Litres per square metre per coat0.75 L/m²
- How many coats2
- Primer per square metre0.2 L/m²
- Total area to treat14.100 m²
- Flat area on the ground12.000 m²
- Area of that upstand2.100 m²
- Membrane to buy15.792 m²
- Rolls to buy2
- Liquid to buy, all coats21.150 L
- Primer to buy2.820 L
- Perimeter of the surface14.000 m
- Per coat10.575 L
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.