Before any renovation, as part of a general inspection, floors should be checked with a level to ensure that no movement has occurred. If there has been a failure of the foundations, the signs will generally be apparent in the unevenness and movement (springiness) of the floor.
If the floor is not level, it may be due to:
- settlement of the foundations due to soft ground and inadequate piling
- missing piles or bearers that may have been removed in a previous alteration
- the floor joist span being too great for the size of the joists.
Deterioration of subfloor framing is generally caused by rot or borer. If there are signs of moisture to bearers, they should either be jacked up from the pile (after cutting any fixings) so damp-proof membrane can be inserted and the bearer lowered and refixed or, if the damage is severe, the bearer or a section of the bearer should be replaced.
Evidence of insufficient piles will be indicated by movement (springiness) in the floor when walking across it. New piles and perhaps bearers should be installed at mid-span where the movement occurs to provide more support.
Subsidence of the foundations may indicate that the house was built on unsuitable ground such as deep organic topsoil, peat, soft or expansive clay, or uncompacted backfill. If this has occurred, it is most likely to be evident from cracking of the stucco cladding and interior water ingress. It may also be indicated from a heavier element such as the chimney that has settled, cracked and is out-of-plumb. If poor soil and settlement is suspected, get the advice of a qualified structural engineer. Soft ground conditions are usually as a result of wet soils, so the cause of the damp ground should be addressed. Once the soil has dried, bearing should improve, but in some cases, it may be necessary to install an additional bearer to spread the load more effectively.