Governing Method
A takeoff, not a specification. Measured surface areas are summed, multiplied by the layer count you declare, and — only if you supply the coverage rate published for your chosen product — divided into material units.
A_total = Σ A_i ; A_treat = A_total × n ; units = A_treat / r Where:
-
A_i= Measured area of surface class i [m²] -
A_total= Sum of measured areas [m²] -
n= Declared layers per surface [layers] -
r= Coverage rate of the selected product (user-entered) [m²/unit]
Derived Equations:
A_total = Σ A_i A_treat = A_total × n units = A_treat / r How the Calculation Works
Each surface class (basement wall, basement slab, wet room floor, wet room wall, roof, tank) is measured separately. A surface you leave empty is not measured — it stays null and is listed as such. It is never treated as zero, because “this project has no tanks” and “the tank area has not been measured yet” are different engineering facts.
Multiplying the measured area by your declared layer count is arithmetic, not a product claim, so it is calculated. Dividing that by a coverage rate is a product claim, so it is only performed when you enter that rate yourself.
Worked Example (illustrative figures)
- Measured areas: basement walls 220 m², basement slab 640 m², wet room floors 96 m²
- Measured total: 220 + 640 + 96 = 956 m²
- Declared layers: 2 → area to treat = 956 × 2 = 1,912 m²
- Coverage rate: not entered → material quantity remains unresolved
The last line is the important one: no rate means no purchase quantity. Enter your product's published rate and the tool will divide 1,912 m² by it.
Assumptions & Limitations
- No application rate, layer thickness, lap allowance or wastage factor is built in — all are product-specific and must be supplied.
- Does not confirm that a given surface is appropriate to waterproof; that remains a design decision.
- Upstands, terminations, penetrations and drainage falls are not modelled.
- Unmeasured surfaces are reported as unmeasured, not as zero.
Frequently Asked Questions
Why does the material quantity say "unresolved"?
Because coverage rate is a property of the specific membrane or coating. EngiMetric holds no product database, so rather than assume a rate it leaves the quantity unresolved until you enter the one published for your product.
Can I use this to select a waterproofing system?
No. It takes off area for a system you have already specified. Selection, detailing and suitability are design decisions.
What happens if I leave a surface empty?
It is reported as "not measured" and excluded from the total. The tool will tell you which surface classes are still outstanding.
Engineering Disclaimer
Engineering Note: This is a measured-area takeoff. It is not a waterproofing specification and does not confirm system suitability. Final areas, layers and materials must be agreed with the designer and the product manufacturer.
Technical References
- Coverage rates, layer counts and lap allowances must be taken from the published data sheet of the selected waterproofing product.
- Waterproofing to below-ground structures: requirements are defined by the applicable project code and specification.