Maintenance, and prevention of wood rot
Windows, doors and frames should be regularly inspected and repainted to protect the timber against moisture. A little bit of regular time and maintenance can save you a lot of headache and expenditure later.
Water can penetrate below the surface layer of paint before there are signs of decay so, if you suspect decay, check all woodwork by pushing the tip of a small screwdriver into the frame at regular intervals. Soft, spongy areas should be cut away and replaced with new timber. If the wood is found to be satisfactory, make good the screwdriver holes with filler and touching in the paintwork. Otherwise, these small holes will give rise to decay later.
Cutting out rotten wood
When removing the original paint be aware that, being old, it may contain lead and should be stripped with chemicals rather than a hot air gun. Lead testing kits are available to check this.
Use a sharp chisel and utility knife to chop out the decayed areas.
Keep both hands behind the chisel blade when cutting and wear work gloves and safety glasses to avoid splinters.
Remove about 10mm of the undamaged wood all around the repair.
If you cannot cut out all the possible areas of rot, drill holes in the timber and insert wood hardening tablets.
Fitting new wood
Neaten the patch by cutting straight edges and forming a dovetail shape at the ends to 'lock' the new piece of wood securely in place.
Cut a new piece of timber of the same type as the original frame, leaving the wood slightly oversize so that it can be tapped into place with a hammer for a good tight fit.
Treating the wood and making good
Treat all the bare wood with two coats of a clear exterior preservative.
Follow all the manufacturer's instructions when working with wood preservatives and make sure the room is well ventilated if working inside.
Glue the patch, and using an offcut of wood to protect it, use a hammer to tap it into the gap. Leave it overnight to set before planing and sanding the surface flush.
Repair any small cracks and holes with wood filler. Be generous as filler tends to shrink as it dries.
Make sure that all work is sanded smooth, then prime, undercoat and paint on your topcoat. When painting on the topcoat, remember two thin coats are better than one thick coat which can cause drips and sags. Only dip about one third of the brush in the paint. Brush the paint on, brush out in short horizontal strokes and finish with long vertical strokes.