Trench fill foundations, also called narrow strip foundations are a narrow and shallow foundation.

The trench is excavated, commonly with machines, and then the ground is back filled with concrete to just below the ground level. Bricks can then be laid on top. This avoids excavating a wider area, as bricklayers are not required to access the trench to lay bricks or blocks. It also helps reduce the width of the foundation whereas below ground brickwork would require a wider footing.

Note

• Suitable for areas where soil is loose (although can be difficult to predict the quantity of concrete required) and/or areas with a high-water table

• Can be taken deeper in areas with heavy clay

• Mesh reinforcement is often required to help resist against ground strain

Advantages of Trench-filled Foundations

• Can save on labour and time

• Cost effective

Disadvantages of Trench-filled Foundations

• The height of the concrete can create access problems for drainage

• Can cause issues with landscaping and planting