Repairs: joinery, doors and kitchens

Joinery - the basics

Timber quality

Much of the wood in use today is of comparatively low density when compared with some of the more slowly grown timbers of yesteryear. So newer timber may be prone to excess shrinkage than some of the more seasoned and densely grown timbers.

Timber is generally stress graded by looking at the density of the grain and counting the number of knots. There are machines available to do this. Some of them work better than others. The British Standards on visual strength grading methods were both updated in 2007:

There is a scheme of European ‘CE’ marking for timber components to verify their fitness for purpose, and the British Standards also set out a variety of guidance for the stress grading of timber and its performance standards.

There have been instances where the stress grading of timber for constructional purposes may not have been wholly reliable, and certainly it is comforting when you see a good tradesman examining material visually and rejecting anything not suitable for purpose.

Sustainability

Ideally, timber should be from a well-managed source. This is essential for some social housing schemes, for example, where the use of certified timber products will score better in environmental assessment schemes such as the Code for Sustainable Homes.

There are a number of timber certification schemes, the Forestry Stewardship Council (FSC) being one of the most well known.

In general, timber components achieve higher environmental scores than, say, PVC products, which are manufactured from petrochemicals and are less easily recycled than timber-based components. (Although recycling of some plastics is possible, there is a carbon impact for that process too, over and above the original manufacturing.)

Timber 'substitutes'

Timber substitutes such as plywood, medium-density fibreboard (MDF) and chipboard offer some considerable advantages over timber. They are all relatively dimensionally stable, so shrinkage gaps are unlikely to appear around joints and details. MDF moulded door linings, architraves or skirting boards can be particularly successful in this regard. They are also quick and easy to fix and do not require any ‘knotting’ or ‘stopping’, which can spoil the paintwork (if omitted) with a conventional timber.

These products can also be fairly cheap.

But there are some disadvantages. For example, standard grade chipboard is particularly prone to damage when wetted, and there are numerous failures under flat roof decks or in kitchen and bathroom floors. Where chipboard sheet is used, cutting out localised sections to replace damaged parts can be problematic.

There is also a question mark over the sustainability of these products. Composite materials such as MDF or chipboard can generate quite a low score in any environmental assessments due to:

  • the problems with recycling this material at the end of its life;
  • the amount of energy used up to create the material in the first place (the embodied energy); and
  • the health and safety risks associated with their manufacture and during construction' from fine dust particles and from the release of formaldehyde. A zero-formaldehyde MDF is available (Medite ZF), but it is imported from Germany and is more expensive.

Woodwork glues

Over the last 20–30 years, use of ‘2-pack’ resin products has grown. These glues can deliver effective repairs at relatively low cost, where replacement of a whole window (or door, etc.) might otherwise be required.

There are various sorts of 2-pack resins on the market, but all will have a ‘pack’ of resin and a ‘pack’ of catalyst (hardener) that is mixed in to cure the compound. Many of these incorporate some form of bulking agent within the resin, such as a powder or fibre compound. However, one or two companies manufacture 2-pack resin systems that incorporate ‘neat’ resin with no bulking agents. These offer a very effective repairs option because once bonded to sound timber (extremely careful eradication of all rotted components or softened timber is necessary) a very good adhesion can be obtained. The resin can be planed and shaped as if it were timber and is sufficiently plastic to accommodate movement due to thermal and moisture content changes.

The 2-pack resin is mentioned regularly in this section: these resins offer an extremely adaptable and effective method of carrying out repairs, which otherwise would require an expensive and highly skilled craftsperson, or perhaps would require wholesale replacement of large sections of window or door frame. However, 2-pack resin does need to be properly used; failure to correctly prepare surfaces for bonding will lead to a rapid failure of the repair.