Base plate, fixed and swivel
A steel plate with spigot that spreads the load of a scaffold leg; the swivel type tilts to sit flat on sloping ground while the leg stays vertical.
Also called: fixed base plate, swivel base, swivel jack, foot plate, sole plate fitting
Stand a 48.3 mm scaffold tube directly on the ground and under load it will punch into asphalt or soil like a stamp. The base plate spreads the force of one leg over a larger area and gives the tube a firm, centred seat. It is one of the plainest parts of a scaffold and one of the most basic.
Two different components go by this name: the fixed plate without height adjustment and the swivel base that adapts to a sloping surface. The adjustable version with a thread is covered under base jack.
The two types
- Fixed base plate: a square steel plate with a welded spigot or tube stub that the leg slides over. It is used where no adjustment is needed: tube and fitting structures, props and shoring, smooth hall floors. Some plates have holes for screws or ground pins to stop them moving.
- Swivel base: the plate is connected to the spigot or jack by a ball or pin joint, so it can tilt while the leg stays vertical. Often the joint is combined directly with a jack, which is then called a swivel jack.
Both are almost always galvanised steel; swivel versions are usually reinforced because the load is no longer introduced quite centrally. Typical places for a swivel base are roofs, embankments, ramps and steps. Permitted tilt angle and load differ noticeably between manufacturers.
Fitting on level and sloping ground
- Check that the ground can carry the load; on soft ground lay a sole board first.
- Place the plate centrally under the future leg position; a fixed plate needs a horizontal surface.
- On a slope, set the swivel base so the plate bears over its full area and the spigot stands vertical.
- Secure plate and packing against sliding, for example by screwing, nailing to a timber sole or with stop battens.
Many instructions accept wedge-shaped packers as an alternative to a swivel base, as long as they are also secured against sliding. On steeper slopes a separate check of the load path is often required.
Frame or modular scaffold?
At the foot the systems hardly differ. On a frame scaffold the frame leg sits on the jack or plate; on a modular scaffold a base collar goes on first. Tube sizes are standardised, but spigots and nuts vary by system.
What to check on used plates
- Lay the plate on a flat surface and check that it does not rock; a domed plate never bears fully again.
- Move the joint through its range: it must be free without rattling. Seized or worn joints are scrap.
- Inspect the weld at the spigot, especially on older parts, and compare the spigot diameter with your system.
Fixed and swivel bases are offered alongside the base jacks.