Creaking or squeaking floorboards are usually the result of loose boards and when walked upon they creak. The board may rub off another, a fixing nail or joist. There are many reasons for a loose floorboard, but the main ones are use of incorrect nails or nails too far apart due to inadequate nailing. The solution here is to screw-fix the board to the joists to secure the boards. You cannot introduce nails or it will do further damage to ceilings etc.
The screws should be fixed at 400mm centres in both directions and consideration should be given to countersinking the screw head into the floor board. At all times check for pipes or cables before screwing.
Another cause may be an unsupported end joint between floorboards. To resolve this the floorboard falling short of a support must be lifted and an extension added to the joist to support the board end. As this will involve cutting the tongue of the board to be removed it is not a simple DIY job but one for an experienced carpenter.
If this simple approach does not work, you need to investigate further.
Other considerations include problems with the joists supporting the boards. These may have twisted due to shrinkage or poor workmanship during construction. They may also be undersized for the floor span and result in sagging of the floor joist. This can lead to movement between the board and joist resulting in creaking. There may be a need to add additional bridging pieces at regular intervals across the floor to strengthen it. However, this is a big job involving lifting of the floorboards.
It is also worth checking the joists to see if an overzealous plumber or electrician has drilled excessive holes in the joist to facilitate a plumbing pipe or cable resulting in a weakening of the joist. Joists should also be fixed solidly at either end of the span on to the wall or a joist hanger and spaced at 400mm centres usually.
One last thing to consider is expanding heating pipes which expand and move slightly when they warm up which may cause the floorboard to make noise if it rubs off a heating pipe. A droll carpenter suggested to me the use of talcum powder, while I’ve no doubt would work for a short time, but it is not a long-term solution.
Pat McGovern is a chartered building surveyor and member of the Society of Chartered Surveyors Ireland.