What plywood is best for beam formwork?
Film-faced plywood, 18 to 21 mm, for both the beam soffit and the side panels. Match the EN 636 bond class to your reuse target: a melamine-MUF Class 2 panel for moderate runs, or a phenolic Class 3 panel such as Pro Form for high-repetition or fair-face beams, up to 20 reuses.
What thickness of plywood for a concrete beam form?
18 mm is the working baseline. Move to 21 mm for deep beams, wide bearer or tie spacing, or fast pour rates where the thinner panel would deflect. Thickness works with the support layout, not instead of it, so set the bearer and tie spacing first.
How do you handle concrete pressure in a deep beam form?
A deep, narrow beam concentrates lateral pressure at the base, rising with pour rate, lift height, and concrete temperature. Follow the formwork designer's pressure calculation per ACI 347 or CIRIA 108, and spec the bearers, studs, and ties to that pressure. The plywood is the casting face, not the structural safety factor.
How many times can beam formwork plywood be reused?
Up to 10 reuses for standard melamine-MUF panels, up to 15 for higher-melamine-content Form Extra, and up to 20 for phenolic Pro Form, all maximums. Reuse depends on release agent use, careful stripping that protects the arrises, and re-sealing cut edges between pours.
Why does my beam form leave a bowed or marked arris?
It usually points to panel deflection from ties or bearers spaced too wide for the pour rate, or a corner panel that lifted during the pour. Tighten the support layout where the pressure peaks and keep the corners flush. Edge swelling more often means an unsealed cut edge, so check the sealing and storage first.
