When Building a new home or adding an extension to an existing property to increase living space or add a garage for storage and parking we need to start with a solid foundation.

Stable Foundations »

Strip Foundations

Normally about 600mm wide and at least 150mm thick; a concrete strip foundation is cast in a trench at a level below the riske of frost or ground movement. Brickwork or Blockwork is then built above ground level. On sloping sites the strip foundation may be built in overlapping steps to gradually change levels and reduce the risk of differential settlement.

Trench Fill Foundations

Trench Filled foundations are created by casting a trench of suitable depth to prevent settlement and frost heave with concrete to a depth about 150mm below ground level. They are very popular in clay soils.

Special Foundations

When a structural engineer specifies atypical foundations based upon the load bearing and movement characteristics of the land allocated for building purposes we use the term Special Foundations:

Raft Foundations

A reinforced concrete slab is poured with a thickened edge to help spread loads across weakened soil structures where differential heave or settlement is likely to affect building integrity. They may often be used to reduce the risk of mining subsidence.

Pad and Beam Foundations

Concrete is cast into a series of bases designed to take reinforced ground-beam foundations in a similar way that lintels carry the load across the top of a door or window frame.

They are often used when deep foundations are needed to offset shrinkage and heave due to the water demands of nearby trees.

Pile Foundations

Similar to Pad and Beam. They are used when excessive depths are needed. Steel Cased or concrete piles are driven into the ground and used to support concrete ground beams.

Foundations When Adding Vertical Extension

Adding a first floor extension to a bungalow or loft conversion to a 2-storey house should not require additional groundwork

They will add a considerable amount of weigh-load to the existing foundations and the risk of subsidence should be considered when adding an extra storey to an existing property or over-garage bedroom or office.

Ground Floor Slabs

A concrete ground floor slab will typically be cast onto a hardcore base, damp-proof membrane and some form of insulating material.

The load is placed directly onto the ground and floor settlement needs to be considered

Suspended Timber Floors and Concrete Beam Floors

A thin concrete sub-floor will usually be layed on a dam-proof membrane to prvent growth of vegetation and dampness.

The load is transferred via the load-bearing walls to the foundations so foundations need to be designed to take this extra load compared to a standard concrete floor slab.