Method · checked 29 October 2026
Beam and base underpinning
A reinforced concrete beam picks up the wall and carries it to concrete bases at chosen points, sized to the ground.
Facts on this page checked against each source on 29 October 2026. Each one links to its source. How we check
Beam and base underpinning is a more engineered version of mass concrete underpinning. A reinforced concrete beam is built below, above or in place of the existing footing, and the beam carries the load of the building to mass concrete bases cast at chosen points (Wikipedia).
How it works
- The beam spans between the bases and picks up the wall. Its design depends on the layout of the building and the loads on it (Wikipedia).
- The bases are mass concrete, placed at designed points. Their size and depth depend on the ground conditions (Wikipedia).
- Clay that swells is allowed for. Anti-heave precautions are often built in where clay soils may expand (Wikipedia).
Beam and base or mass concrete?
| Mass concrete | Beam and base | |
|---|---|---|
| How the load gets down | A continuous run of concrete under the wall | A beam carries the wall to separate bases |
| Digging | Along the whole length being underpinned | Concentrated at the base positions |
| Design | Bay depths and sequence | Beam reinforcement, base sizes and depths |
| Clay that swells | Allowed for in the design | Anti-heave precautions often built in |
Based on the descriptions of both methods in Wikipedia, Underpinning. The engineer decides which suits your house.
Questions to ask
- Why beam and base rather than mass concrete or piles?
- How deep are the bases, and what are they founded on?
- Are there anti-heave measures, and why?
- What happens to the drains along the line of the beam?
- Will the engineer inspect the reinforcement before the concrete goes in?
Questions people ask
What is beam and base underpinning?
A reinforced concrete beam under, above or in place of the existing footing, carrying the building's load to mass concrete bases at chosen points.
Why use beam and base instead of mass concrete?
It lets the load go down at chosen points rather than along the whole wall, with base sizes and depths set by the ground. The engineer weighs it against mass concrete and piles for your house.
What are anti-heave precautions?
Measures built into the design so that clay that swells when it gets wet doesn't push the new foundation up. They're often used with beam and base where clay may expand.
Related
Keep reading
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