What plywood do you use for concrete stair formwork?
Film-faced plywood is the standard choice because the raking soffit often stays exposed and needs a sealed film, not bare veneer. Use 18 mm (3/4 in) for the soffit and risers on typical residential and commercial flights, stepping to 21 mm (13/16 in) for wide flights or architectural fair-face soffits. Match the bond class to how many flights the form will see.
How many times can stair formwork plywood be reused?
It depends on the core glue and edge care. Form Basic (WBP MUF, EN 636-2) reaches up to 10 reuses, Form Extra (higher-melamine-content WBP MUF, EN 636-2) up to 15, and Pro Form (WBP phenolic, EN 636-3) up to 20. Stairs are the most cut-heavy form on the job, so re-sealing every fresh cut edge is the single biggest lever on reuse.
Why are my stair nosings chipping when I strip the forms?
Chipped nosings usually trace to hard stripping rather than a panel fault. The nosings are the most fragile geometry on the form, and prying a riser off against the fresh arris with a crowbar takes the corner with it. Strike with a wedge, work the risers first and the soffit last, and leave form-removal timing to the engineer because a stair carries load early.
When can you strike concrete stair forms?
Form-removal timing belongs to the structural designer and the relevant code, such as ACI 347 or the local equivalent. A stair carries load early, so stripping the soffit before the concrete reaches the specified strength is a structural risk, not just a finish one. Strike the risers and side forms first, and leave the soffit until the engineer signs off.
