Heel and toe foundations are particularly useful on clay ground. When dry, clay is a very solid material, that becomes very soft when wet and is therefore unpredictable as a base for walling. Pressure from behind a wall – even a dwarf one such as shown here- can force the wall forwards creating a pivoting movement.
In order to mitigate this potential problem, a ‘toe’ is added to the front of the foundation, thereby increasing the depth of the concrete by 150mm, and by adding a ‘heel’ to the rear, also by 150mm, the strength of the foundations is greatly increased.
For any substantial wall, over 900mm high, a structural engineer should be employed to produce properly assessed specification based on mathematical equations, taking into consideration a host of other data.
Please note the various steel fabrications that are to be built into the feature, especially the horizontal bars on the main foundation and vertical bars set into hollow concrete blocks (to be filled with wet, strong, rammed concrete). These prevent the foundations from cracking laterally and the walling blocks from shifting off their footings.
A concrete raft under the paving slabs is tied through into the vertical concrete and rebar in the blockwork by means of steel mesh, which overlaps the blocks and is integrated with the horizontal concrete bed being wedded to the vertical.
Please note too, that the face of the blockwork is indicative only. It may be a rendered finish, brickwork or stone clad.
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