Structural formwork plywood

Ecoply F11 17 mm structural formwork plywood from Carter Holt Harvey is the standard specification for concrete formwork used in remedial concrete spalling repair in Australia. F11 denotes a minimum face grade that is appropriate for structural formwork — the plywood is stress-graded with a minimum MOR (modulus of rupture) of 11 MPa in the face direction. At 17 mm thickness, F11 plywood provides sufficient stiffness and bending strength to span between formwork bearers without excessive deflection under fresh concrete and mortar pressure, and to resist the hydrostatic pressure of repair mortar in column and wall forms.

F11 12 mm structural plywood is used in remedial repair work for lighter-duty formwork applications where the full rigidity of 17 mm is not required — shallow slab edge side forms, column side forms with close bearer spacing, light boxing around small repair patches, and temporary containment forms for repair mortar. At 12 mm thickness, the plywood is lighter and easier to cut and handle than 17 mm grade — this is a practical advantage when working in restricted access areas such as carpark columns, beam soffits, and balcony edges where space is limited and sheets must be lifted and fixed in tight locations. Use 12 mm F11 only where bearer spacing is close enough to prevent mid-span bending — a 12 mm sheet spanning more than 300–400 mm between bearers under fresh mortar pressure will deflect visibly.

Film-faced formply is structural plywood with a hard phenolic film bonded to both faces. The film face provides a smooth, non-porous surface that resists moisture absorption, reduces concrete adhesion, and gives a high-quality smooth finish on the cast concrete face. Film-faced formply can typically be reused 8–20+ pours (depending on edge protection and site handling) compared to 3–5 pours for uncoated F11 ply.

Generic F11 structural plywood from local and independent timber merchants is acceptable for concrete formwork in remedial repair where the structural grade is confirmed from supplier documentation. The key requirement is that the plywood must be certified as F11 (or equivalent) structural grade — the F11 designation confirms that the plywood has been stress-graded and meets the minimum structural performance requirements for concrete formwork. Non-rated or off-grade plywood should not be used for structural concrete formwork.