What thickness plywood should I spec for rectangular column formwork?
For sections 200 to 400 mm wide and lifts under 3.5 m, 18 mm phenolic film-faced plywood is the working baseline. Past 400 mm wide, or on a tall single lift over 4 m at a fast placement rate, move up to 21 mm. Lateral 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 will not bend itself into a clean circle, so true round pours usually go to steel half-shells or fibre tubes such as Sonotube. Plywood still earns a place on one-off architectural diameters and on faceted polygonal columns with 8, 12 or 16 sides that read as round at viewing distance. It is also the usual material for small box-outs inside a circular form.
How many reuse cycles can I expect from a film-faced column form?
Phenolic-bonded EN 636-3 panels such as Pro Form are rated for up to 20 reuses with disciplined edge care, and Form Extra, a higher-melamine MUF panel at EN 636-2, is rated for up to 15. Standard MUF grades sit lower on columns, with Form Basic at up to 10 and Eco Form at up to 6, because corner stress and tie-hole wear are harder here than on walls or slabs. Treat these as ceilings, not promises.
When should I choose steel or aluminum modular over plywood column forms?
Past about 30 identical pours, modular forms pay for themselves because strip-and-reset is faster and the finish stays consistent across the run. Very tall single-lift columns over 4.5 m without intermediate restraint also favour modular, since bracing a plywood-faced form that tall costs more than the panel. Anything above ACI Class A architectural finish belongs in steel with a smooth liner.
What kills plywood column forms first, the film or the edges?
Almost always the edges. After two months on site the face film is usually intact, but the corners have bowed and the tie-rod holes are wallowed out by repeated pours and water getting in. Sealing every cut edge, including inside the tie-rod holes, on the day the panel is cut adds real cycles, and so does reusing tie cones instead of driving rods through the face.
Which glue class should column forms use for short runs versus repeat pours?
Repeat-pour column work calls for phenolic-bonded plywood at EN 636-3 (Class 3), which is where Pro Form sits. A short run of three to eight pours can use Form Extra, a higher-melamine MUF panel at EN 636-2 rated for up to 15 reuses. Form Extra's longer life comes from its glue recipe rather than a heavier face film, since it uses the same 165 gsm film as Form Basic.
