How to recognise wood rot in window frames

The first signs of wood rot

Wood rot develops when moisture stays in the timber for a longer period. Fungi then break the wood down from the inside. On the outside you often see little at first: the paint film keeps up appearances for a while, while the timber underneath is already going soft. That is why it is important to know what to look out for.

• Flaking paint or blisters, especially on horizontal parts.
• Hairline cracks in the paint at the joints of the frame.
• Dark or grey discolouration of exposed timber.
• Soft timber: a screwdriver sinks in without much pressure.

Where to look

Water runs downwards and lingers where it cannot drain away. Wood rot is therefore almost always at the bottom: in the sill, in the lower corners of the jambs and where the glazing bead meets the frame. The bottom of a front door and the end grain of woodwork are also vulnerable, because the timber soaks up moisture there like a sponge. Also check the sealant joints around the glass: a loose bead of sealant lets water run behind the paint film.

In Amsterdam-Noord, Zaandam and along the IJ, many homes stand in places with plenty of wind and moisture. Frames and doors facing south-west take the most rain and sun. Check that side first, ideally every spring. A fixed moment for this is described in the article checking your paintwork after winter.

What to do if you find wood rot

Do not wait until the next paint job. A professional painter can still repair a small spot now with a two-component wood repair compound or a spliced-in piece of timber. Wait a few years and the rot can spread into the joint of the frame, making the repair bigger and more expensive. With a wood rot repair, Oranje Kwast shows how a frame looks sound again after repair and painting.

Do not seal a spot you have found with sealant or a dab of paint in the meantime. That traps the moisture, which makes the rot progress faster.

Preventing wood rot

Prevention is easier than repair. Keep the paint film intact, have damage touched up quickly and make sure there is not too much time between paint jobs. How often that is needed is explained on how often exterior painting is needed. If you already suspect rot, request a free consultation via wood rot and frame repair. More tips are in the article preventing wood rot.