What is permanent formwork?
Permanent formwork (also called stay-in-place, sacrificial or lost formwork) is any forming material left in the structure once the concrete has gained strength. It is never struck, cleaned or removed, which saves the whole strike-and-recovery cycle on jobs where that step is impractical, such as pile caps, trench fill or congested sites.
What is the difference between stay-in-place and participating permanent formwork?
Non-participating (stay-in-place) forms only shape the pour and do nothing structural afterwards, for example corrugated plastic, EPS or wire-mesh-and-film systems. Participating (composite) forms become part of the structure and carry load, such as precast concrete planks or profiled steel decking under a composite floor slab.
Is permanent formwork cheaper than reusable plywood?
It depends on repetition. Permanent formwork has no striking labour but you pay the full single-use material cost for every square metre. Reusable film-faced plywood costs more up front but that cost spreads across up to 20 pours. Below a handful of pours the permanent form is usually cheaper; above it, plywood pulls ahead and keeps widening the gap.
Can plywood be used as permanent formwork?
Plywood can be left in place in limited cases, such as a soffit form that becomes a permanent ceiling lining, but that is not what film-faced formwork plywood is built for. It is engineered as a reusable casting face that is stripped and re-poured, so using it as a single-use lost form wastes most of its value.
Which reusable plywood grade suits high-rotation walls and columns?
For elements that go up and down dozens of times, specify an EN 636-3 phenolic-bonded panel such as Pro Form (up to 20 reuses) for European-standard work, or the HDO range for North American formply programmes. For shorter runs, an EN 636-2 melamine-core panel like Form Extra (up to 15) or Form Basic (up to 10) carries the same phenolic face at a lower entry cost.
