The sixth in a series on getting the best out of your buildings
The sound of squeaking floors can be a constant source of irritation. And although an increasingly common problem, squeaky floors are avoidable.

Following good-practice guidelines in design and installation minimises the risk of a squeaky floor. The remedy is usually quite straightforward: screw down the floor coverings, provided the floor is not a sound-insulating floor.

The problem
Particleboard – also known as chipboard – in the form of sheeting or panels is the most commonly used flooring material and typically implicated in squeaky floors.

Particleboard floors may be "fixed" or "floating". Fixed floors are mechanically fixed to a timber joist floor structure or to timber battens on a concrete structure; in floating floors, the particleboard panel is laid over an insulating layer, such as resilient mineral wool batts, to provide improved sound insulation. The particleboard panels of a floating floor are glued together but not fixed to the floor structure or sound insulation layer.

Squeaking may be caused by a single defect, or a combination of several, in design or workmanship, or by the flooring material, or its use. Only an inspection of the floor and the structure on which it is laid will reveal the reasons for squeaking.

Typical causes include an uneven floor structure, a lack of support for the floor panels or where the panel joints are not staggered, the incorrect thickness or grade of particleboard or poor mechanical and adhesive fixing of the flooring.

These issues should be dealt with in both the design and installation of floors. Ideally you should provide specific criteria relating to the floor being built, and not rely on general references to British Standards. Expecting a flooring contractor to plough through the 30-page British Standard 7916 to extract the correct installation guidance is unrealistic and probably unreasonable.

Squeaking may be caused by a single defect or a combination of several, in design or workmanship

What to look out for in design
Uneven or abrupt changes in the level of the floor structure will lead to movement and potential squeaking of particle flooring. This can be prevented by ensuring that timber floor joists and battens are both regularised and deeper than any insulation between them, the surface of a concrete base does not deviate more than 5 mm under a 3 m straight edge and that the surface of a "beam and block" floor is levelled using either a thin layer of mortar or a proprietary levelling screed.

Particleboards shrink or swell equally in all directions, particularly because of changes in moisture. Shrinkage or expansion will distort fixings and result in loose flooring, which gives rise to squeaking. A 2.4 m board delivered to site with a moisture content of 2% could expand up to 4mm when taken into an internal environment. To prevent this, you should clearly state the service moisture levels for particleboard flooring. For unheated areas, the maximum is 15%, for areas with intermittent heating 9-12%, and areas with continuous heating 7-9%.

Floorboard movement can have detrimental consequences if you do not allow for it. Ensure that a 10-12 mm gap is provided around all the floor edges and that floating floors are divided into room-sized bays.

Using the correct grade and thickness of particleboard and adequate protection is important. Particleboard should be to grade P5 (load-bearing for use in humid conditions) or P7 (heavy-duty load-bearing for use in humid conditions) to BS EN 309:1992. Floors in kitchens, bathrooms and other potentially wet areas should be overlaid with a vinyl sheet covering with welded joints and a "coved" skirting to protect the board from moisture – no particleboard is 100% moisture resistant. For continuously supported floors, the thickness of the flooring should relate to the stiffness of the floating or resilient layer, although in no case should it be less than 18 mm. Where the span between joists is 450 mm the particleboard should be 18-19 mm thick. For a span of 600 mm, the particleboard should be 22 mm thick.

Additional support is often key to keeping floors squeak-free. This can be provided by "noggings" at critical points such as the edges of any panels not continuously supported within 50 mm of the face of a wall; the short edges of any tongue-and-groove panels not continuously supported by a joist or batten; to any cut edges that are not continuously supported by a joist or batten; where the floor, or its support, is interrupted by a fireplace or other rigid upstand; and round the edges of access panels, or where high loads are anticipated, at door thresholds for example.