What thickness plywood should I spec for rectangular column formwork?
For sections 200–400 mm wide and lifts under 3.5 m, 18 mm phenolic film-faced is the working baseline. Past 400 mm wide, or where you're pouring tall (over 4 m single lift) at a fast placement rate, move up to 21 mm. The lateral concrete pressure follows the head of plastic concrete at the bottom of the lift, so yoke spacing tightens at the base and opens toward the top.
Can you use plywood for circular columns?
Plywood doesn't bend itself into a clean round. Half-shell steel forms or fibre tubes (Sonotube and equivalents) are the dominant solutions for true circular pours. Plywood enters the picture for one-off architectural diameters, faceted polygonal columns (8, 12, or 16 sides) that read as circular at viewing distance, and box-outs or blockouts inside a circular form.
How many reuse cycles can I expect from a film-faced column form?
Phenolic-bonded (EN 636-3) panels like Pro Form deliver up to 20 reuses with disciplined edge care. Higher-melamine-content MUF Class 2 panels like Form Extra carry up to 15 cycles. Standard MUF Class 2 panels (Form Basic, Eco Form) hit up to 8–10 on column work, where corner stress and tie-hole wear are higher than slab or wall. Those are maximums, not minimums.
When should I choose steel or aluminum modular over plywood column forms?
Past about 30 identical pours, modular amortizes cleanly because the strip-and-reset is faster and the off-form finish stays consistent across the run. Very tall single-lift columns over 4.5 m without intermediate restraint also favour modular, because the bracing required to stabilize a plywood-faced form costs more than the panel itself. And anything above ACI Class A architectural finish goes to steel with a smooth liner.
What kills plywood column forms first — the film or the edges?
Almost always the edges. Walk a job site after two months and the face film is usually intact, but the corners are bowed and the tie-rod holes are wallowed out from successive pours, water ingress, and rough stripping. Three habits add real cycles: seal every cut edge (including inside tie-rod holes) the day the panel is cut, reuse tie cones rather than driving rods through the face, and plug-and-fill tie holes on the strip cycle rather than later.
