What plywood thickness is used for foundation and footing formwork?
18 mm (3/4 in) film-faced plywood is the working baseline for standard strip and pad footings. Move to 21 mm (13/16 in) for deep pile caps, fast pours, and shallow foundation walls where the lift height climbs and backing spacing opens up. Edge-seal every site cut regardless of thickness.
How is footing formwork pressure different from wall pressure?
A tall wall builds hydrostatic pressure with height, so the base of a deep lift sees the most load. Footings are short, but short does not mean low-pressure: fast placement and cold concrete still drive the effective pressure up, and a pile cap filled in one drop can load the form base hard. The formwork designer sets the pressure to the placement rate and concrete temperature per ACI 347 or the local equivalent, not to form height alone.
How many times can foundation formwork plywood be reused?
It depends on the core glue and the care. Form Basic (WBP MUF, EN 636-2) reaches up to 10 reuses, Form Extra (higher-melamine-content WBP MUF, EN 636-2) up to 15, and Pro Form (WBP phenolic, EN 636-3) up to 20. These are maximums under disciplined edge sealing and release-agent use. Foundation work is cut-heavy, so re-sealing every fresh cut edge is the single biggest reuse lever.
Why is the edge of my foundation panel swelling?
Edge swelling may indicate an unsealed cut edge or storage on wet ground, so check the handling and storage history first. Foundation forms are cut to length constantly, and each fresh cut is raw core until it is sealed. A panel that arrives flat and sealed on all four edges is within spec; what happens to it on site is where reuse is won or lost.
