There is no substitute for properly sealing the timber before it is built in and exposed to the elements.

The most important part of ensuring that timber lasts is to prevent moisture from penetrating the timber cells. Before any wooden joinery is built in or exposed to the elements, it must be properly sealed on all faces and edges.

Manufacturers usually supply joinery items with a sealer coat. The products look more attractive, and the sealer does give the timber some protection. However, this is never sufficient. The sealer is usually light, penetrating oil that provides temporary protection only, and dries out quickly.

There is no substitute for properly sealing the timber before it is built in and exposed to the elements.

If the manufacturer’s sealer is still “tacky”, the timber should first be cleaned down with mineral turpentine to remove any surface oil, dust or other surface residue.

If you’re painting your timber, it should be lightly sanded and then painted with a good-quality timber primer. It is helpful to use a “pink” primer, to distinguish it from the undercoats and finishing coats. Then the timber should be sanded again. The primer raises the grain, and if not sanded at this point, it will be difficult to obtain a good finish afterwards. The timber should then be painted on all edges and surfaces with a universal undercoat.

If the timber is to be sealed with a natural oil or varnish, it should also be sanded first. The first coat of the sealer should be thinned with the correct solvent, to aid penetration of the timber cells. It should be sanded again, and a second sealer coat applied before the timber is exposed to the elements.

Use a good-quality penetrating timber preservative rather than a varnish. Although the varnish will give a hard, strong surface, it tends to crack when it weathers, allowing moisture to penetrate and become trapped in the timber. This leads to more rapid deterioration. The varnish is difficult to strip, which must be done before it can be re-varnished. A timber preservative provides a more flexible surface coat that can be easily over-coated after cleaning down and lightly sanding the surface.

It is good practice to apply a waterproof coating to the backs of frames where they will be in direct contact with brickwork. Bitumen, aluminium primer, pure acrylic, roof paint or carbolineum can be used.

Preparation of openings:

Joinery is either built in during the erection of the brickwork, or installed in prepared openings when the brickwork is complete.

Make sure the joinery is not placed under load at any stage; that it is properly supported; and that proper damp-proofing and waterproofing measures are taken.


Timber needs to be protected from physical damage during construction. Although good sealing of the timber will protect it from the sun, the rain and from mortar stains, it also needs protection from the other hazards of a building site.

This is especially important when the timber has a natural finish, as it is very difficult to repair timber in such a way that it is not obvious to a disappointed owner. The cost of protection is always less than the cost of replacing damaged joinery.

Tip of the week

MacAlister’s favourite topic – fires in winter: We see more house fires in winter than at any other time of the year. Please be extra vigilant around your electrical appliances.

Overloading your supply will lead to fires. You are using more lighting, heating and cooking than at any other time of the year, so instead of using more extension leads or double adapters, be systematic, move things around, switch off whatever else you can when using heaters. Switching off includes not leaving things like your TV on standby – this also uses electricity, and can cause power surges if the electricity goes on and off. Please be careful.

Winter brings with it power outages, so we turn to candles, which are just as dangerous if left unattended. A draft will blow them over and, before you know it, something has caught alight. And don’t leave a log fire burning unattended when you go to bed.

Do you have a fire extinguisher ready, just in case? - Weekend Argus