Timber Window Repairs

By Andy the stuff doer

FULL STEP BY STEP window repair methods here

Timber windows can easily last more than a human life time. As long as the details are right and they are well maintained they should be any real bother at all.  Unfortunately the maintenance bit is often neglected or done with unsympathetic materials.  So we often come across serviceable windows that  are suffering from bits of rot.

This doesn’t always mean the window has reached the end of it’s life this series of articles explains how even extreme repairs are possible to keep the window going for many years to come.

Click through for full series of articles, and please leave any questions or comments below.

START HERE to read the FULL STEP BY STEP window repair methods


  • Full investigation to see exactly what a repair will need
  • Making good the timber frame or sash
  • Curing other window problems, double glazing and draught proofing:- replacing parts, fixing loose joints, swollen sticking sashes, fixing hinges
  • Filling and Sanding window repairs
  • Glazing and Putty
  • Priming and painting

rotten window ready for repairspliced in window repairfiller repairputty glazinglinseed oil painted window

21 Responses to “Timber Window Repairs”

  1. Hi I have an 1882. Sash.window and I need to replace the bottom sash glass . It is one piece about 3 feet by 1 1/2 feet wide it has on the inside beading all around and on the outside it has putty to 3 sides the top being a wooden bar as I don’t wish to damage this bar could you tell me the correct procedure for removing the glass regards Gary

  2. Hi Gary, Apologies for the delay in responding my email notifications aren’t coming through. You need to remove the putty on the outside. It is easier to do if it’s warmed up. As you are replacing the glass anyway and it does matter if it gets broken just use a heat gun and an old chisel. Once the three sides are clear working the glass might free it from the groove. If not heat the putty and chip or scrape some out, again heat will help. You could also try it with steam. Hope that helps, if it’s not too late.

  3. Hi Andy,i have had two bottom sash windows made to replace existing which is quite rotten at the bottom rail corner joints.Looking at the closing edge at the bottom of the windows i can see where the bottom rail meets with the sill part of the frame is angled probably done for draught reduction and water egress my question is: is this a set angle and any other things to watch out for.thanks Karl

  4. Hi Karl, The angle on the bottom rail should match the angle on the sill (cill). The sill and bottom rail should also have matching steps in them, half way across the bottom rail. The sash should rest on top of the step on the sill, the bottom of the step should have a gap to sash bottom rail. Having a gap on the outer side of window allows water to drain away and allows ventilation of this damp area. If it was tight on sill then water would end up being drawn in and wouldn’t be able to evaporate so the timber will rot, particularly up the end grain of the sash stile. The sill can also suffer under the permanently damp conditions.

    You might also want to consider the internal corner where the outer lining , bottom of pulley rail joins the sill. This is also a moisture trap. I cut the outer lining back at this point to allow water to drain on new windows. On refurbishing old windows this would expose end grain so it better to add a small fillet of filler so water is shed away from the corner.

    Hope this helps


  5. Hi Andy, I have sash windows which I am trying to improve. On the inside on the bottom of the glass particularly the sealing on the inside of the glass is loose in parts [and easily pried out. What sealant/filler should I use. Putty? or should I use an Epoxy wood filler? Look forward to your remarks.

  6. Hi Brian, A proper job would be to dig out the loose bits, scrape out the slot and re-pack with linseed putty but be careful that the glass stays stuck to the external putty. I would avoid using Epoxy filler unless I was using it to repair the timber as well. If it was just a few bits that had come loose I might be tempted to fill in the voids and smooth over the rest with an acrylic sealant as a quick and easy way to get a surface to paint over.

  7. Hi Andy, I have sash windows which I am trying to improve. On the inside on the bottom of the glass the sealant on the inside of the glass was loose and easily pried out. I filled the gap with ‘Multi Purpose’ putty and forgot about allowing it to skin before painting ! It felt fairly firm when I painted it with Dulux water based primer (‘for difficult surfaces’), but a few days later I noticed cracking in the surface going deeper into the putty ! I realize now I should have given the putty longer to set.
    Can I redeem the situation now to avoid digging it out and starting again, but avoid future cracking — as it will be more difficult for access after I position kitchen units in front ?

  8. Hi Mike, Apologies for the slow response, I’m getting loads of spam problems.

    The two main causes of cracking putty I have come across are
    (a) The putty used is too wet with the linseed oil (the modern stuff has solvents in it so it dries out and shrinks instead of slowly oxidising). The putty needs to be quite stiff until you work some heat in to it, you can soak excess out by rolling it on newspaper.
    (b) The timber is very thirsty and it sucks the linseed out. This is why it’s a good idea to coat the recess with shellac first (difficult in your situation)

    So that’s what to look at for the future, as cure in your situation, injecting some good quality decorators caulk in the cracks should do the trick internally. A bit of a cheat but hey lifes too short to dig it all out again.

    Hope that helps

  9. I have a 1940s house that has been hit with termites. The major problem is that they virtually destroyed two windows. I want to keep the original design, so I have to do a rebuild. I have some windows I salvaged from another house, but need help building the sliding window casement. I have watched several videos and read several articles, so I have the basics down, but I need some details on how to determine sizes and what casement design to use (I have seen several designs and don’t know which is best).

    Any help along these lines would be greatly appreciated. A video would be great!!


  10. I’ll be doing some more on the windows and plans as soon as I can

  11. We have original small pane casement timber windows, originals from the 1920s whem the house was built. Were going to get the externals sanded and repainted/reputtied next yr.
    My question is can we convert from conventional paint to linseed oil paint? Is this doable?

  12. Hi Sarah,
    Apologies for the late response. Yes if the old paint is removed and you’ve got it mostly all down to bare wood. The linssed paint won’t give the advantages if it’s over old paint.

  13. Hi Andy

    Thank you so much for all your fantastic advice. Really helpful. I’ve been looking on online for buying Shellac and getting confused. Can you recommend a good brand and where you buy it from?

    Many thanks


  14. Hi there, really interesting read on sash Windows. It is an area I would love to get into and wondered if you ran any course on sash restoration. I would love to retrain and offer it as a service. I live in Brighton and there are many many sash Windows in need of repair. Please get in touch.

    Thanks in advance


  15. Hi Mark, apologies for the late response. Sorry I don’t run courses or now of any specifically for sash windows. A joinery course should equip you with the basics and then you could specialise and have a few other strings to your bow.

  16. Hi Andy, super instructions for replacing/puttying small panes, just not sure about how to fit my quadrant beading to the inside of the frame – do I need to use putty to the back of the beading too ? Many thanks, Terry

  17. Andy
    Really appreciate your site. It helped me a lot rebuilding my fireplace.
    A question about sash windows – do you tend to remove the sash from the frame, or is it possible to do the whole lot (strip paint, repairs, repaint) in situ, with the window in tact?

  18. Jeremy Brooks on July 16th, 2019 at 6:18 pm

    Dear Andy, your really helpful article on putty talks about consistency.
    You mentioned leaving some on newspaper to reduce the oil. How long as a starter?
    Bearing in mind it’s 20/21C currently can you give me a steer? I am laden with linseed putty that sticks to the hand/knife and anything else in range before I can get it onto the external rebate. Best regards, JB

  19. Hi.

    We have an area of wet rot on one of our outer windows which is being replaced.

    We have also found some areas of soft, dry, flaky wood in other windows. All on the outside areas.

    I’ve been looking at ronseal wet rot hardener to treat this before filling, but I’m not sure if it is rot or something else, as the wood isnt actually wet on these other patches.

    They’re all small areas so I’m hoping to fix it myself if possible, just not sure if I can.

    Thanks for any advice.

  20. Hello Andy, thank you for a marvellous article on re-furbing old windows. But one question I’m not quite clear on . . . after removing all old putty and brushing down the wood frame, is the new putty applied to the raw wood, or can one/should one first apply a coat of primer or paint. My windows get quite a lot of weather and also, because they’re single glazed, suffer quite a bit of condensation on the inside.
    I know you suggested shellac to stop the wood sucking the linseed out of the putty but will this give any lasting degree of protection against water ingress as the re-glazing ages?

  21. Thanks for this website, very useful!

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