Whether that means a repair or a new window comes down to how much sound timber is left and whether the sections were well made in the first place.
How to test what you've got
Press a bradawl or a screwdriver into the bottom rail, the cill and the bottom of each stile. Sound timber resists; decayed timber takes the point with almost no pressure. Check the joints at the corners — an open mortice that has been filled repeatedly is a sign the frame has been moving for years.
Look at the glazing too. Failed putty or a perished bead lets water straight into the rebate, and no amount of external paint will hold that back.
Splice repairs done properly
A splice means cutting the decayed section out back to sound timber, machining a matching piece in a durable species, and bonding and pinning it in with a structural adhesive. Done well it is invisible under paint and lasts as long as the surrounding frame.
Filler-only repairs are a different thing. Two-part fillers have their place for small defects, but a filled bottom rail traps moisture against the timber behind and typically fails again within a couple of winters.
When new joinery is the better call
If more than roughly a third of the frame is going, or the sections themselves are too slim to hold modern glazing, a new window made to match the original profile usually costs less over its life than repeated repairs. In conservation areas and on listed buildings, a like-for-like replacement in the original detail is normally the route that gets approved.
We make replacement casements and sashes from the original profiles so sightlines, horns and glazing bars match what was there.
Common questions
Can rotten windows be repaired in place?
Small splices and cill repairs can be done in situ. Anything involving corner joints or a full bottom rail is better done with the sash or casement taken out to a bench.
How long does a splice repair last?
Where sound timber is left to bond to and the repair is properly primed and painted, a splice lasts as long as the rest of the frame. The paint system matters as much as the joinery.
Can I put double glazing into an old frame?
Sometimes. Slim-profile units can go into deeper sections, but many original sections are too thin without altering the sightlines, which conservation officers will look at closely.
What timber do you use for replacements?
Durable hardwood or engineered, slow-grown softwood depending on exposure and budget. We'll explain the trade-off before ordering anything.