Repairs: floors and flooring

It can be difficult to persuade building owners to allow the necessary time, cost and disturbance to carry out comprehensive checks when flooring repairs are needed. Also, laminate flooring reduces the scope for checks beneath boards. However, checks are worth it in the long run.

Ensure that you are quite clear about the scope of the inspection when confirming terms of engagement, and make the building owners/clients aware of the risk of a limited inspection.

Consider using a Protimeter™ hammer probe to take moisture readings at some depth in joist ends. The probes can also be hammered through floorboards if you do not have permission to lift floor coverings. However, the 50–60mm probe depth may only provide limited information, and it is probably unwise to rely on it in isolation.

For ground floor work:

• Allow for continuity of sub-floor ventilation. (Solid floors can easily block and interrupt airflows to other parts of the building. So too can new walls and partitions; even if they are vented, the loss of airflow may be critical in a large building.)
• If there is a cellar or basement beneath the main timber ground floor, you may need to consider repairs in the manner of a first floor, but with added regard to protecting the ends of any joists or wall plates that might come into contact with the comparatively high risk band of wall at the damp-proof course/ground level intersection.
• In some cases you may need to incorporate a suitable membrane to resist radon gas. This can be complicated; and careful detailing at the perimeter of the walls/floors is generally required to prevent any routes for ingress of radon gas. Sometimes a secondary radon barrier on the oversite is required in addition to a ventilated void.

In Walls, the importance of using lime mortar joints and pointing where these were the original jointing materials was stressed. This is even more important where there are solid walls and joists have been built into or rest upon them. Portland cement pointing can rapidly elevate the moisture content of the wall and trigger problems such as wet or dry rot in the joist end bearings (which could spread rapidly).

First floor joists can suffer from end bearing problems too. For example, the original bearing could be inadequate, or damp penetration through a solid wall could cause deterioration of the timber over time. Frequently, poorly executed alterations, such as notching for heating pipes, causes weaknesses to develop. In the former, the cure is generally similar to that detailed above.

When carrying out refurbishment and alteration works, ensure careful detailing of pipe runs where these have to be embedded within the floor – preferably using some form of proprietary ducting, rather than casting the pipes into the floor.

Where this must be done, it is imperative that suitable lagging is put round the pipe to reduce risk of both condensation and damage to the service pipes. (The cost, disturbance and upset caused by having to dig out defective service pipes embedded in the screed is considerable.)

The basics should serve as a useful aide memoire when you are out on a site inspection.