Refurbishing timber floors

In this excerpt from her book Timber in Refurbishment, author and journalist Ruth Slavid explores how to approach the refurbishment of old timber floors.

As floor boards shrink (a process that has been exacerbated by the introduction of central heating), gaps will open up between them. There are a number of approaches that can be taken. If the floor is of enormous historic significance, it may be that one just lives with the gaps, but these evidently reduce both thermal and acoustic integrity, as well as allowing debris to fall through and become trapped.

The way to achieve a new 'perfect' floor is to lift all the boards, introduce a new strip at one side to take up the slack, and then relay all the boards. There are two possible problems with this. One is practical – that the boards may be damaged in the process of lifting and relaying. The other is to do with retaining historical authenticity. It is important to number the boards as they are removed and relay them in their original sequence in order to retain the 'original' floor.

The Society for the Protection of Ancient Buildings (SPAB) recommends that floorboards should only be lifted when essential. This should be done, it says, by a competent carpenter, not by an electrician or any other tradesperson needing to get access beneath the floor. Where access is needed regularly, SPAB recommends 'discreet screwing' rather than nailing, with beeswax used to disguise the heads of the screws.

Where it is considered desirable to keep the boards in their original positions, but the gaps between them are unacceptable, then a more fiddly operation can take place. This is the introduction of fillets of the original timber in the gaps between the boards. Evidently, the nearer the fillet is in moisture content, the better the result will be. Although in some ways this is a more 'authentic' solution, it will result in a greater loss of character.

This is certainly not the first instance in historic buildings where there can be a conflict between historical authenticity and the feel of a place. SPAB also recommends using papier maché or beeswax for filling gaps.

The other, and more serious, problem with floorboards is cupping. This is where the moisture contents on either side of the floor board are different. As a result, it curls up at the edges like an old sandwich. The simplest, most brutal way of dealing with cupping is to sand down the surface of the timber. However, if the moisture content issue has not been dealt with, this will be only a temporary fix. The board will cup again. The correct thing to do, is first to deal with the problem, by identifying the source of excess moisture. This is probably causing damage elsewhere in the building, so is well worth doing. Meanwhile, the boards should be dried out in a temperature- and humidity-controlled environment, before being returned to the newly tempered environment. SPAB recommends first wetting the concave sides and then applying weights as they dry.

Peter Kaczmar, TRADA Technology's flooring specialist, highlights the need to investigate the moisture condition of old floors before renovation. This is particularly important for floors at ground level in buildings that were not originally heated and/or where central heating will be added or improved, which introduces a moisture differential between the upper and lower surfaces.

With high quality timbers that have acquired a patina, cleaning should be done with great care. The surface should not be sanded off, but should be cleaned carefully with turpentine. Then it should be waxed and sealed with carefully chosen products.

It is not just the timbers themselves that should be authentic. Various materials have been used over the years as 'pugging' to create a seal between floorboards. These also play a vital part in the appearance of the floor, and should be preserved where possible, or replaced with similar materials.

Jasper Weldon has a list of three golden rules for floors:

• Always seek advice from an expert before allowing other trades to work in the building
• Where possible, avoid the use of heavy sanding equipment
• Do not use water to clean the floor.

If floors are beyond saving, then new floors can be created, either by using salvaged timber from elsewhere, or by using new timbers of the appropriate species, and cutting and treating them in an historically correct manner.

© TRADA Technology

Extracted from Timber in refurbishment by Ruth Slavid, TRADA Technology 2010 with RIBA Publishing, £30, available from RIBABookshops.com.

Related NBS information:

Articles:

• The appeal of timber
• Recycling our heritage

Selected links:

• Timber, including laminated
• Timber bibliography

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