Creaking and cracking floorboards?

Creaking floorboards are very common for us to find when conducting a snagging survey in new build houses. The location of where it occurs can often move through the settlement process or dissapear altogether after time. Having said this, most of the houses we inspect months after completion still have creaking floors.
The most common reason for floors creaking are:

• The use of incorrect nails holding the floor down to the joists. In the case of chipboard floors these nails should be annular ring shank nails. These nails (usually 2 inches long) have serrations all round the shaft and are slightly screw like in appearance. There may also have been an insufficient quantity of nails used.
• The floor joists need to be absolutely solid and of the correct size to prevent movement across the span they are bridging. A joint study at the University of Salford with the NHBC identified the worst noise came from the junction between the joist, block work party or external walls and the plasterboard wall/ceiling lining
  

It is important that the joists are fixed very solidly at either end, are spaced at the correct centres (usually 400mm) and cannot move in their wall sockets or joist hangers. The tail of the hanger should be firmly built into the wall and the joist firmly fixed into the hanger. If the joists are built into the wall this should be done in a way which prevents both rotting and movement.

Whilst a slight creak can be easily solved by accessing the fixings under the carpet, often customers encounter a cracking noise which indicates more severety and requires structural work such as installing noggins.