Often, due to budgetary restrictions, it is necessary to construct only a part or section of a scheme, with the full plan being implemented at a later date as funds permit. These truncated works usually involve paving or walling. As the concrete foundations for either are being constructed, it is useful to consider a method of permitting additional works to be added, whilst retaining the same strength of foundation as the initial works.
Taking paving as the first example, if the first stage of development is finished against (say) planting or turfing, simply extend the reinforcing bars (or adding new ones for this particular purpose if none were set into the original concrete) by at least 75cm into/under the bed/lawn. If, and when the works are completed, you will have a strong, semi-monolithic ‘complete’ foundation of equal strength under all the paving.
If the works do not go ahead, you have still acted in a thoughtful manner on behalf of your client.
Walling foundations will obviously vary in width and depth according to the wall under construction. However, the technique is the same no matter how large the dimensions.
At the point where the foundation for stage one is to terminate, set into place a piece of timber (preferably old scaffold board rather than plywood, as it is easier to break off at a later stage) to act as the end of the concrete footings.
Drill appropriate sized holes through the wood and insert reinforcing bars – I tend to use 18mm – into the wet concrete mix, extruding at least 90cm beyond the works, and 120cm minimum into the foundations. Once the concrete is set, the board should be removed, leaving the bars at approximately 15cm centres protruding from the foundations, preferably in a double row, top and bottom.
All of this work is below ground and has no visual effect on the scheme, but this forward planning means that the next phase can be added, with, once again, semi-monolithic foundations.