Pads and ground beams

How it works

The load reaches the ground not continuously but at points. Between the points a ground beam runs, which:

• ties the pads into a system,
• receives the wall, giving continuous bearing for the bottom track,
• evens out the differences between the points.

When it is economic

Where the bearing stratum is deeper

The pads can be taken down to the right layer without excavating deep beneath the whole building.

Where the load is small

For a light structure the load on each point is modest, so small pads are enough.

Where less concrete is wanted

Less material, less excavation, less spoil to remove.

What has to be solved

The floor construction

With pads the floor is generally an independent structure: either a ground-bearing slab or a suspended, ventilated floor. That determines the build-up and the insulation too.

The thermal bridge of the ground beam

A continuous beam can form a thermal bridge unless it is broken or insulated.

Uplift

The mass of a pad is small, so the tension from wind suction is more of an issue here than with a heavy raft. Resisting uplift in light structures.

The exact position of the points

A panelised structure tolerates setting-out error poorly.

The link with ground screws

The logic of point load transfer is the same as with ground screws — there a driven steel element simply replaces the concrete pad. Understand one logic and you understand the other. The principle of ground screws.

The point

Point foundations work where the load is small and the bearing stratum is deeper. The key question is the ground beam: it is what turns the points into a system.