Soft, flaking timber around a window doesn't automatically mean you need a new window. In St Helier, most rotten frames we see can be repaired well, provided the rot is caught early and the right method is used. This guide explains how to judge the damage, what a lasting repair involves and when replacement really is the better choice.
Our coastal weather is hard on joinery. Salt air, driving rain from south westerly gales and long damp spells over winter all attack paint on the weather faces. Once the paint cracks, water gets into the end grain and stays there.
Rot almost always starts in the same places: the bottom rail of the sash, the sill, and the joints where the sill meets the upright jambs. South and west facing elevations, especially on terraces near the seafront and around Havre des Pas, tend to fail first. Frames that have been painted over repeatedly without sanding back or re-puttying also trap moisture underneath.
You can do a simple first check yourself. Push a small screwdriver or bradawl into any suspect timber. Sound wood resists. Rotten wood feels spongy, or the tool sinks in easily.
Check these points on each window:
For small, localised rot, the usual fix is to cut out all the decayed timber back to sound wood, treat what's left with a wood preservative, then fill with a two part flexible epoxy resin system designed for exterior joinery. Once primed and painted, a well done resin repair can last many years. Cheap rigid fillers tend to crack as the timber moves, so they're rarely worth using.
Where a larger section has gone, such as most of a sill or the bottom few inches of a jamb, we splice in new timber. Using a durable hardwood or modified timber like Accoya, glued and pinned into the old frame, gives you a repair that often outlasts the original wood. A whole new sill can usually be fitted without taking the window out.
As a rough guide, a single resin repair might cost from around £80 to £250, and a splice or sill replacement from around £250 to £600 per window. The final price depends on access, how many windows are being done at once, and how much hidden rot turns up once the timber is opened up.
Repair isn't always the right call. Replacement is usually better value when:
A lot of St Helier's older housing stock is Listed, and many streets in the town centre carry heritage protection. If your property is Listed, replacing windows normally needs planning permission from the Government of Jersey, and a like for like timber replacement may be expected rather than uPVC. Planning policy generally favours repairing historic windows over replacing them.
Repairs that match the existing profiles and materials usually don't need permission, but it's worth checking before any work starts if you're unsure of your building's status. Keeping original sashes and glass through careful repair is often the simplest and cheapest route for historic homes.
No. Almost all window frame decay is wet rot, which stays local to damp timber and stops once the wood dries out and is repaired. Dry rot is rarer and can spread into masonry, so it needs a wider investigation.
If all the rotten wood is removed and the repair is primed and painted properly, a good resin repair can last ten years or more. How long it lasts depends mostly on keeping the paint in good condition, especially on exposed elevations.
Small, shallow patches are manageable for a confident DIYer using a proper exterior epoxy system. Anything involving sills, joints or sashes that don't close properly is best looked at by a carpenter, as hidden rot is often more extensive than it appears.