London sash window refurbishment projects – today we will be replacing a sill section. To splice a sill section we need to remove stiles, inner window board, and in most cases inner cheek will need splicing.
Before we remove anything, we carefully measure the sill section, once we disturb the frame with sill removal we will never know the exact size required. The other benefit is we can cut our sill section and house it out correctly before removing the old one. This preparation is important because it allows us to quickly rebuild the framework once sill completely removed. It id not easy to board up, or screw sash without a sill section, and the draughts coming through the frame are quite significant.
Once sill is spliced out, we splice the sill stiles and front cheeks. The sill is then dropped in, window board re-attached, and then new spliced stiles are neatly inserted, screwed, and glued to give the frame strength once again. We will use an epoxy filler to fill any screw holes and joints. Once set the filler is sanded, and the sash window repairs primed and undercoated ready for decoration.
One thing to note. When cutting out the old sill we must do so as gently as possible to not cause any damage to the internal plaster work. There may be a timber plate under the sash. If this is the case then it can vibrate, very easily, causing plaster directly under the sill to fall off with very little pressure applied. This can only be avoided by being very conscientious. Sometimes however, you may be flat unlucky and the original window installer may have hammered 6 inch nails to the sill as the main original fixing. The chances of avoiding minimal damage is slim. If it does happen then the remedy is a bag of one coat plaster, rapid setting. Do not waste time using thistle and then skim. You will not be able to produce a finish that warrants the effort because of the joint. Instead patch as neatly as you can with one coat plaster, allow to set, and then sand the joint if troweling up didn’t provide a respectable finish. This solution is much more real world, eventually you will re-skim the entire wall and then a beautiful finish can be achieved. This is all part of sash window refurbishment. Another aspect I won’t go into fully on this post is double glazing existing sash windows. We should be looking to make upgrades to improve the environment and lower our fuel bills where we can.
All repairs are typically spliced with Pine wood as this is the material the window originally made with. London sash window refurbishment specialists can also be contacted if you feel this is beyond your level of DIY capability and it is wise even if you do not wish to have the work carried out by someone else, that you at least check the viability of repair first. Maybe email a few window companies and hope that one kind soul will give you some useful information. Normally a repair or replacement sill will cost in the region of £120-£160. It’s a healthy saving if you feel up to the challenge. A professional is unlikely to cause such damage to the wall – although as outlined, in some situations it’s possible and unavoidable. If your looking for a sash window refurbishment company in London then feel free to leave a comment, or if you’ve recently used one, please also leave a comment reviewing the company in question
Interesting article could you upload a few pictures of the process please?
Pictures added Tim, hope this helps. I can send you more detailed if you like?
ok great so I cut through the sill and pull the sill out through the stiles. Presumably I just cut the sill back in behind the stile that are removed and house it in? Thanks for your help.
Yes that’s more or less it Tim, sorry for the slow and late reply I do this as a hobby to help people and have been extremely busy at work. You should have a couple of images in your inbox, should you need anymore help on this might be worth giving me a quick call I’d be happy to spare you 15 minutes, I believe with your skills this will be no problem. Cheers
What is the best shop in London to buy sill from. I visited a few local places and they don’t stock it, I got told it’s kinda specialist and not used all that much so expensive to keep in house. Any leads would be much appreciated as I am near Brixton and I don’t have a car so need to carry it home!
Hi Perry, thanks for you’re interest. In Brixton I wouldn’t mess around, go straight to Acre Lane Timber these guys are the real deal for all window profiles. They also have hardwood sill section and the pricing is trade. Good location to be if you need to look after your sash windows.
Would you have any recommendation on the filler and sealant used against the brickwork to seal the frame once the seal is installed? Also what primer and undercoat is the best to use to ensure the joints don’t open on the timber splices.
I personally use two part epoxy resin and silicone to deal the stone to the sill. Then I prime with Dulux Weathershield always. There is no value in using cheap paint here, you want the repair to be well sealed, and this paint will not crack if the timber swells or moves.
I’ve got a problem with the sill. I am trying to remove it but it appears to be fastened from the underside and I am at risk of damaging the plaster surrounding. Is there any usual fixing position I might of missed. Or if screwed from underside, how would you remove to avoid damage internally?
Hi Jonathon,
I highly recommend you cut the sill into more pieces. This way you’ll hit the fixing or at least remove sections of timber that are not fixed, once there is more wiggle room things will far smoother. You should use your other hand with leverage against the timber plater underside to stop the force moving this plate and damaging plaster internally.
I need to replace my sill section and I was wondering the carpenter who is doing it told me it might be a good idea to put damp course under the sill. I have not seen this in any tutorials or guides, could you tell me why please? Thanks Sarah
No, do not use damp course, in all my years experience it creates a moisture trap. I have removed so many sills with damp course, that are normally installed by carpenters believing they are doing the right thing, when in fact it’s a breeding ground for the dreaded dry rot.
Hi there, I have a lower rail that’s come loose and I am thinking about using an L bracket to support it. Would you recommend any other solution. I am not sure I am capable of removing the sash although I have seen that L brackets cause problems over time? Could you help me?
Hi Chris,
Remove the staff bead on one side of the window. Then gently remove the sash without cutting the sash cords, it should just balance, you then have access to the mortice and tenon. Firstly re wedge and then glue. This should be sufficient without mechanical fixing if you can allow ample curing time for the epoxy resin. If you’re in a rush you can use a mechanical fixing to take the strain initially, but please do not only use a screw, it won’t last. and the joint will split easily again.
In the picture you’ve shown of the sill being cut out, I can see you’ve cut up the frame as well. This is extremely difficult to do and my saw wont get into the gap. Do you have any tricks that are going to help me produce an excellent finish into the corner? Also I would like to know how do I fix the front timber afterwards so that it’s all structurally good? I appreciate your responses.
Hi Sarah,
To get in the corner and make a neat 90 degree splice you need a specialised Japanese handsaw that has a fine tooth blade for precision cutting. I warn though, they are not cheap, mine is £50 and the blades cost more than a regular handsaw. If you want to do the job properly then you need this tool. Fixing the front cheek is simple. Once you have housed out the sill correctly then you’ll screw the front cheek to the sill first, then countersink and screw the face edge joint to the old timber. This is why it’s important to use a good saw and disturb the frame as little as possible. Then you can fix once a again after the pulley stile is installed, This will give more than enough structural strength, however be sure to resin the joints and ensure resin oozes from them. this helps to create a water tight seal and stops potential cracking and movement over time which will reduce the life of the repair.
We are in Chelsea and own a large eight bedroom property that requires all sash windows to be refurbished. The windows need stripping, and some timber splicing repaired as I have found on your website. The windows also need a draught proofing system and possibly double glazing depending on the budget. Would you be interested to quote on this?
Regards
Lars
Hi Lars,
Yes would love the opportunity to quote on this. Please let me know the best number to get you on and I’ll call and organise a survey for the restoration work. I’ll be in the area most of next week so feel free to let me know when is convenient? Regards