Uneven floors are often a sign of problems with the foundations.
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. Other things to look for include sticking doors or doors cut on the bottom edge.
If the floor is not level, it may be due to:
- deterioration of the original timber piles
- missing piles or bearers that may have been removed in a previous alteration
- not being levelled when it was repiled
- soft ground that has resulted in subsidence
- the floor joist span being too great for the size of the joists
- damaged floor joists.
Deterioration of piles and/or subfloor framing is generally caused by rot or wood-boring insects (see borer and rot). In most cases, the perimeter piles are the first to deteriorate as they are more likely to be subject to frequent wetting (Very dry timber is less susceptible to fungal or insect attack.)
If the floor slopes away from the chimney, this may indicate that the piles have deteriorated. If there are signs of moisture to the bearer, it should either be jacked up from the pile (after cutting any fixings) so damp proof course can be inserted and the bearer lowered and refixed. If the damage is severe, the bearer or a section of the bearer, should be replaced.
Movement or springiness in the floor may be evidence of missing piles. 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, the heavier elements such as chimneys and masonry walls are likely to have settled, cracked, and be out-of-plumb. If poor soil and settlement is suspected, get advice from a qualified structural engineer.
Soft ground conditions are usually caused by the soil being wet, so the cause of this moisture 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.