Roof-terrace waterproofing calculator
The primer goes on, then each roll unrolls with its 10 cm overlaps and the upstands round the edge.
The drawing
- Primer
- Roll
- Overlap
- Upstand
What you need
| Material | Calculated need | To buy | Unit price | Total |
|---|---|---|---|---|
| MembraneSBS bitumen membrane 4 mm — 10 m² roll | 10 rolls | 10 rolls | ||
| Cold primer — 20 L bucketCold bitumen primer — 20 L | 20 L | 1 bucketexactly what you need | ||
| Cold primer — 5 L bucketCold bitumen primer — 5 L | 10 L | 2 bucketsexactly what you need | ||
| Indicative total | ||||
Working out prices…
The formula
80 m² + 36 m × 0.2 m of upstands = 87.2 m²; one roll covers (10 − 0.1) × (1 − 0.1) = 8.91 m²; 10 rolls per layer; primer 87.2 × 0.3 = 26.16 L.
The assumptions
- 10 cm side and end overlaps.
- Dry deck with existing falls and outlets.
How to use it
Measure the terrace and choose the upstand height.
Choose one or two layers and the finish.
Read the rolls and the primer, and add it all to the bag.
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