Mr. Thomas Campbell:

A common issue we have come up against in Mayo, in Donegal and other counties are situations where the home was constructed with an excessive amount of blockwork below ground level, typically greater than 900 mm below ground level. This would have been done during construction to get to a suitable bearing capacity whereby one had to excavate deeper to get to a solid area. Under the current scheme, that excessive amount of blockwork needs to be removed, replaced and built on the existing strip foundation. There are a number of practical issues with that from a construction point of view and a health and safety point of view. If it is the case that the house is in a housing estate there would be quite a deep excavation required adjacent to the public footpath and to the other properties. If it is a house in the countryside there could be excess costs around landscaping where one must take it back and dig a deeper hole. A very practical solution to this is to remove the defective blockwork, remove the infill hardcore that is there, replace the hardcore in compacted layers and then create a reinforced concrete raft up closer to ground level where one has poor ground conditions. This is what the designs do and it is a very practical solution.. By today's standards, where there is excessive blockwork below that is greater than 900 mm, and the infill stone is greater than 900 mm, one is required to put in a precast concrete slab at floor level to span between the blockwork. This is to carry the house and carry the floors because hardcore greater than 900 mm is susceptible to settlement. From a cost point of view, doing a reinforced concrete raft versus the blockwork and a precast slab would probably work out cost neutral but it is very much a more robust and practical solution from a construction and building point of view.