What thickness plywood suits commercial slab formwork in Australia?
Eighteen millimetre film-faced on 400–500 mm joist centres is the commercial soffit default for pours around 150–200 mm deep. Australian form-ply buyers use the same span logic when specifying slab decks for multi-storey programmes. Use 21 mm when centres push past 500 mm or the pour is deeper than 200 mm. Match thickness to span and deflection limit, not habit.
How is slab formwork different from wall formwork on a pour programme?
Wall formwork takes lateral pressure that peaks at the base. Slab formwork sits flat and carries the full dead weight of wet concrete plus crew and bar live load. Sag becomes a permanent wave in the soffit, so stiffness across the joists matters more than on a buried wall. Buyers search form ply for slab because that soffit is often the finished ceiling.
How many reuses can slab formwork plywood take under good site care?
Reuse is up to N on the mill card. Eco Form Plus up to 8, Form Basic up to 10, Form Extra up to 15 under MUF EN 636-2, Pro Form Lite up to 15 under PF Class 3, Pro Form up to 20. Floor count is not a cycle count. Same-day clean, edge sealer, and flat stacking protect the card for Australian formwork yards.
Should slab formwork plywood get a release agent before the pour?
Yes. Coat the face before the sheet goes down. Once rebar is on the deck you cannot coat evenly. A thin, even film helps strip and protects the phenolic overlay on commercial slab pours. Miss a patch and the next pour can take film with it.
Can regular plywood replace form ply on a commercial slab deck?
Not for a reusable soffit. Bare construction plywood lacks a sealed overlay and a formwork glue class, so alkaline paste bites the face and edges swell fast. Spec film-faced grades or North American HDO and MatteFace for commercial programmes. Save bare ply for buried work that will not be stripped and reused.
Is Form Extra Class 3 for slab soffits on Australian jobs?
No. Form Extra is Superior Glue MUF under EN 636-2. The extra cycles versus Form Basic come from glue chemistry, not a Class 3 upgrade. If the engineer named EN 636-3, spec Pro Form Lite or Pro Form instead for the soffit RFQ.
