Post-Cast Strip Calculator
Enter strip length, width, slab thickness and waterstop size to get concrete volume plus waterstop length and weight.
Inputs
Result
Formula
| Concrete volume | V = total length × width × thickness |
| Waterstop length | L = total length × number of lines |
| Weight per metre | g = width(m) × thickness(m) × 7850 (kg/m) |
| Total weight | W = L × g × (1 + waste %) |
30 m of strip, 0.8 m wide, 0.2 m thick, 300×3 waterstop both sides: 4.80 m³ concrete, 60 m of plate at 7.07 kg/m, 437 kg including 3% waste.
FAQ
Why must the waterstop flange face the water side?
The bent flange goes toward the water side — outward for basement walls, downward for base slabs. Seepage then has to travel around a lip that is pressed tighter as pressure rises. Installed backwards it becomes a channel and cannot be corrected after casting. Flanges are typically 30-50 mm, welded both sides.
When can the post-cast strip be poured?
Settlement strips wait until the main structure tops out and settlement stabilises (usually at least 60 days). Shrinkage strips are specified at 42 days minimum, often 60 in practice. Before pouring: clear debris, scabble the interface, derust the bars, use one grade higher with an expansive agent, and cure for at least 14 days.
Waterstop plate or swelling strip?
The steel plate lengthens the seepage path and is welded, so it is durable and reliable for higher pressure — basement slabs and walls. Swelling strips compress the gap by absorbing water; easy to install but not for high pressure, and their swell capacity fades with long immersion. Using both in critical locations is common.
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Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.