Last Updated on October 26, 2026 by Royal Stone Care
Unfortunately, the issue of wood which has become rotten is one that many of us will face at some point, whether that’s a decaying window sill or anything else.
Ultimately, you need to do more than just slap on some filler, make it smooth and paint over it and hope for the best. The problem will just come back and the timber will continue to rot below the filler. But the good news is that repairs with modern products can be long-lasting and effective.
And, most of the time, you can treat wet rot without having to replace the wood entirely, whether you’re working on a doorframe, decking or anything else.
Wet or dry rot?
Understand whether the rot is dry (i.e. caused by moisture) or wet (caused by excessive moisture). In fact, many experts consider dry rot to be more destructive and dangerous than the wet version. And that’s because it can spread further and more quickly. Wet rot tends to confine itself to a more limited space, and needs constant moisture.
So you’ll first need to assess the cause and the extent of the problem. And you can then avoid any future rot by dealing with any underlying causes of fungal growth or moisture.
Repairing rot: here’s how
First of all, ensure the area is dry, and get rid of any wood which crumbles away easily. If large bits of timber come away, or the wood won’t stop crumbling, then you may be looking at a replacement job.
Drill little holes into the rot, and ideally slightly beyond it to prevent spread.
Next apply a wet-rot wood hardener to the timber using a brush. And apply it liberally before leaving it to penetrate the wood.
Use a wood hardener from a decent brand on the affected area. It will then soak into the rotten wood before setting, hardening the timber once again. Follow the manufacturer’s instructions to give it enough time to dry thoroughly. You can then fill in any remaining gaps with an appropriate wood filler.
Once it’s dry, your wood should once again be healthy. Scrub off any excess or residual hardener with a wire brush. And, finally, use a filler to smooth out the repair, to finish off the job.
To finish, sand down the filler to leave the surface nice and smooth. And you can finish with a stain or paint so that it matches the surrounding wood.
Epoxy wood filler
This is something you can use to repair and restore wood which is rotten. Just fill in the affected areas with it – it will then bond with the remaining solid timber.
Wood patching
This is another option, and involves taking away the part of the wood which is affected. You then replace it with a new piece of timber.
Preventing rot in the first place
Proper ventilation is one of the best ways to stop rot from occurring. Open windows or use a humidifier. Don’t allow droplets of condensation to form and sit in place for a long time.
Repair initial cracks promptly, as this stops water from coming into contact with your timber.
The good news is that modern wood is often pre-treated so it should resist rot. And if you’re buying this material for fencing or decking, make sure it’s OK to be in contact with the ground, as this can often cause the problem.
Protect your wood in decking by clearing it of any standing water whenever possible. After all, that’s just good basic maintenance.
We can help
Royal Stone Care isn’t just for natural stone restoration! We can help private homes and businesses with wood restoration, repair and sanding in London. So if you have rotting wood and want professional help rather than attempting the job yourself, get in touch.
