Technical guide
Screed Volume and Wastage, Explained
The volume ordered for a pour is never exactly area × depth — and it shouldn't be. Here's the honest reason why.
Get your volume calculated properly
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On paper, calculating how much screed to order looks simple: multiply your floor area by the depth and you have the volume. In practice, every legitimate quote adds a small margin on top of that theoretical figure, and it's worth understanding why — it's not padding, it's realism.
Uneven subfloors, minor over-pour at edges, and the simple fact that a pump can't be run down to the exact last litre all mean real-world usage sits slightly above the theoretical number. Running short mid-pour is far more disruptive than ordering a sensible margin.
This page explains how we calculate volume and why the wastage allowance is there — genuinely useful context whether you're comparing quotes or just curious about the number on yours.
The basic calculation
Volume (m³) = area (m²) × depth (m). A 60m² room at 50mm depth needs a theoretical 3m³ of screed. That's the starting point for every quote.
From there, we add a wastage allowance — typically a modest percentage — to account for subfloor unevenness, minor spillage and the practical limits of dosing a pump precisely to zero.
What causes real-world volume to exceed the theoretical figure
- An uneven subfloor needing extra material in low spots to reach a flat, level finish
- Perimeter edge conditions and detailing around door thresholds
- Small losses in the pump line and hose at the end of a pour
- Rounding to the nearest practical batch or truck load size
Illustrative example (indicative only)
| Item | Value |
|---|---|
| Floor area | 60m² |
| Target depth | 50mm |
| Theoretical volume | 3.0m³ |
| Typical wastage allowance | Small percentage on top, confirmed at survey |
Get your volume calculated properly
Send us your area and target depth and we'll show you the theoretical volume alongside a realistic allowance.
A quote with zero wastage margin isn't more accurate — it's just optimistic. A sensible allowance protects your pour from running short on the day.
— Exeter Liquid Screeders
Volume & Wastage — questions we get asked
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Get your volume calculated properly
Send us your area and target depth and we'll show you the theoretical volume alongside a realistic allowance.