Ordering too little plywood stops the cycle; ordering too much ties up cash. A simple area-based calculation gets you close before the first quote. This article shows the formula and one worked example you can copy into a spreadsheet.
The example uses round numbers to show the method. Replace them with the contact areas from your own drawings.
Key Takeaways
- Sheets in circulation = formwork contact area ÷ sheet area, plus wastage.
- A standard 8 × 4 ft sheet covers about 2.98 m².
- Plan how many floor sets you keep in circulation, not only one.
- Judge cost on cost per pour: sheet price ÷ repetitions.
The Formula
- Find the contact area for one pour: slab soffit, beam sides and bottoms, column and wall faces, and edge forms. Use the drawings.
- Divide by the sheet area. One 2440 × 1220 mm sheet is about 2.98 m².
- Add wastage for cutting and openings. 8% to 12% is a common planning allowance; adjust for your layout.
- Multiply by the sets in circulation. If a floor is poured while the one below is still propped, you need more than one set.
Sheets = (contact area ÷ 2.98) × (1 + wastage) × sets in circulation
Worked Example (Illustrative Numbers)
| Item | Value |
|---|---|
| Slab soffit area | 400 m² |
| Beam sides, bottoms and edge forms | 200 m² |
| Column and wall faces | 200 m² |
| Total contact area for one pour | 800 m² |
| Sheets before wastage (800 ÷ 2.98) | about 269 |
| With 10% wastage | about 296 sheets |
If you keep one set in circulation, you need about 296 sheets. If your cycle needs two sets, double it. Do not copy these figures: your areas will differ.
Planning Reuse and Replacement
A sheet used once per floor is used once per pour. Over a 30-floor tower, one set is used about 30 times if sheets last. In practice, cut-up sheets near openings wear out first, so budget a top-up allowance rather than assuming all sheets last equally.
Rated repetitions are an upper guide that depends on handling. Edge sealing, release agent and careful stripping extend life; see how to increase repetitions.
Turn the Quantity into a Cost per Pour
Cost per pour = sheet price ÷ number of repetitions achieved. A higher-priced sheet that reaches more pours is often cheaper per floor. The price guide and why cheap plywood costs more walk through this comparison.
Frequently Asked Questions
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