Single glazed windows and what the putty is really doing
A traditionally glazed window is a single pane of glass sitting on a bed of putty in a timber rebate, faced off with putty on the outside and pinned with small glazing sprigs. There is no sealed unit and no bead — that outer fillet of putty is the only thing keeping water off the rebate. Once it dries out, shrinks and starts falling away, rain gets straight into bare timber. So what looks like a cosmetic job is usually the thing standing between you and a rotten frame.
Re-puttying properly
The old putty is raked out, the rebate cleaned back and any bare timber primed before anything else happens. Skipping that primer is the single most common reason fresh putty fails within a year: dry wood pulls the oil straight out of it and it perishes early. The glass is re-bedded, sprigged and faced off, and where a pane has to come out it goes back on a fresh bed rather than sitting on the old one.
New putty has to be painted
Linseed putty needs a couple of weeks to skin over, then it must be painted — with the paint carried a millimetre or two onto the glass to seal the joint. Left unpainted it dries out and cracks up within a season. If you are painting the window yourself we will tell you when it is ready rather than leaving you guessing.
Leaded lights: what actually goes wrong
A leaded light is small panes — quarries — held in H-section lead came, soldered at every joint and then cemented to make it weathertight. Three things fail. The cement perishes and the panel starts to rattle and leak. A pane cracks. Or the whole panel bows out of flat, usually in a large window with too few support bars, and the lead has stretched.
Repairing rather than replacing the panel
A single cracked quarry can be cut out and replaced in situ without disturbing the rest of the panel — the lead is opened up, the piece swapped, and the joint re-soldered and re-cemented. A bowed panel usually has to come out to be flattened and supported properly. Lead does have a life, and on a panel over about a century old it can be too brittle to work, in which case it is re-leaded using the original glass.
Matching the old glass
Most of the difficulty in these jobs is the glass, not the lead. Old obscure and textured patterns went out of production decades ago and the colours in a Victorian or Edwardian panel are rarely a straight match to anything current. We will tell you honestly before starting whether we can match a pane closely or only get near it, so nobody is surprised by the finished job.
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Certass registered · PWF Trusted Installer · £5m public liability · 40 years' experience
Common questions
Can you replace one cracked pane in a leaded window?
Yes, usually without taking the panel out. The lead around that pane is opened up, the broken piece removed, the new one fitted and the joints re-soldered and re-cemented. There is no need to re-lead a whole panel because of one pane.
Can you replace a single glazed pane rather than the whole window?
Yes, and it is the usual job. A cracked or broken pane in a single glazed timber window is measured, cut to size and bedded back in on fresh putty — the frame, the sash and the paintwork all stay as they are. We can put the same glass back in, or use toughened where a pane sits low down or beside a door and safety glass is now required.
My putty is cracking and falling out — do I need a new window?
Almost certainly not. Perished putty is a maintenance job, not a failure of the window. The exception is where water has already been getting in long enough to rot the timber underneath, and even then it is often a repair to that section rather than a new frame. We will tell you which you are looking at.
How soon can new putty be painted?
Usually two to four weeks, depending on the weather — it needs to have skinned over but not fully hardened. It does need painting: unpainted linseed putty will not last.
Do you work on listed buildings and in conservation areas?
Traditional putty glazing and leaded light repair are generally what those properties require, since like-for-like repair is expected rather than replacement. Check what your own consent says before any work starts, as the rules differ from one property to the next.
Is it worth repairing rather than swapping to uPVC?
For a period property, usually yes. Repair keeps the character that the house is worth money for, it costs less than replacement, and in a conservation area a uPVC swap may not be permitted anyway. We will give you the price for both if you want to compare.
Where we cover
single glazing, leaded lights and putty across the West Midlands and the towns around it, including: