Bay window replacement



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I will be working on this house soon and will be doing a full renovation on it. All the windows will be d/g, but i have never tackled a bay window before.

Can anyone tell me how difficult they are to replace in PVC. Would it be easier to keep the bay and replace the damaged timbers where necessary ?

It is currently single glazed so i would also be looking to uprate to 12mm double glazed units if i keep the wooden frames.

Any hints / tip on renovating this feature will be appreciated.
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The windows look like they could be structural, I don't know how you deal with that?
quite possibly. The other one in the photo is in good condition and looks like it has been renewed in the last 10 yrs. The houses were built in 1935.

The top right bay window has dropped and you can see the towel which is used to plug the gap.
Retro fitting double glazed units into timber windows is not as easy as it sounds. Doing it correctly would mean adapting the frames to give drainage and ventilation around the units and would be very expensive. If you just bung in some double glazed units without doing it properly you will be lucky if the units last 2-5 years.

Replacing the windows in PVC would probably be your best option. The windows will be structural so will need proper corner posts with bay pole jacks. It will need signing off by building control or a Fensa registered company.

Get some quotes from local company's.
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I wouldn't advise DIYing structural bays, theres just too much that could go wrong, let it go wrong for a pro not yourself, you pay a bit more but you get it signed off and you get a guarantee
I wouldn't advise DIYing structural bays, theres just too much that could wrong, let it go wrong for a pro not yourself, you pay a bit more but you get it signed off and you get a guarantee

And if it collapses mid-job, they can make the call to their insurer!
Who the homeowner or the contractor?

The contractor - getting a pro in reduces the risk of collapse (if they are any good!), but if it was to happen its their liability, not the home owners.
Who the homeowner or the contractor?

The contractor - getting a pro in reduces the risk of collapse (if they are any good!), but if it was to happen its their liability, not the home owners.


You might also find you might not be covered on your own buildings insurance if you did attempt it DIY, there could possily be some exclusions on carrying out structural work yourself
Ok thanks for info.

Because it is structural i think it is best to keep the wooden frame as it is and adapt it for double glazed units and do wood repairs to cill where rotten. Gazman has mentioned this is difficult and fiddly.

So can you tell me if i have cocked up on the other bay window in the photo.

The upper section is d/g'ed, but the lower section is single glazed. I had a young lad break 4 of the panes in the lower section and so rather than put in single again i ordered 12mm d/g units and just siliconed them in and put new beads in place.

So based on what gasman has said i must have cocked up here. What should i have done. the units cost me £25 each so not breaking the bank.
The frames should be routed out so that the edge seal of the unit (approx 12mm) seal and spacer bar are protected from the sun and elements. There also needs to be at least a 5mm gap all around the unit for venting water vapor.

Then you need drainage holes. It dosent mater how well you seal the glass in water vapor will get in there and it needs to be able to get out.

Whatever you do don't use normal window putty. The linseed oil in putty is one of the worst things for breaking down the seal on double glazed units.

If you diy it and do a good job the glass units may last 5-10 years. Do a bad job and you will need to replace them every couple of years when they mist up on the inside.
Treat what you've done so far as a temp repair but don't throw good money after bad at thses windows, dg units probably wouldn't even last 2 years never mind 5, put the money into 2 new bays
If the glass at the bottom of the windows is 800mm or closer to the internal floor it will have to be toughened.

Tbh the glass is about 60% of the cost of new PVC windows and the wood in those windows looks close to beyond repair in places.
You will probably spend about £400-500 on glass and several days of labor and painting only for it all to need redoing in 5 years.

Get some new windows now and save the hassle. Your probably looking at about £800-1200 per bay (depending on the spec) for all new windows with a 10 year guarantee and be fairly confident they will outlast you with minimal maintenance.
glass is £28 sq/m so about £300 for the whole bay approx.

When you say per bay do you mean both top and bottom or just one of them?

If the bays are structural how do the pvc guys replace what is there? Do they start from bottom or top ? Do the pvc windows become structural then ? Are they reinforced with steel because pvc windows are not that strong are they.
It may indeed be structural. So if/when the windows are replaced they will usually need to support the bay with acro props during the installation. You also must ensure that the windows that will replace it (if you choose upvc)are fully reinforced. Upvc frames are not designed to take loads. They will slowly warp (unless reinforced) and the structure above may slowly collapse over the years. I would also agree that it is best to get a company with experience to do the job and who are fully insured for any mishaps.....

Is this your house? To live in or to rent out?

Now, I am going to get my conservation hat on....sorry....

When you say "renovate" try to avoid the temptation to gut the place and rip out any originality the property may have. As you may come to regret it in time.

Please, please try to retain what look to be very nice original features.

The leaded lights on the windows and that 1930s front door. is much easier to rip out and put in upvc...but you can loose so many wonderful details. Don't fall foul of thinking brand new is best.

Ok...I concede the windows are not the best example of 1930s window architecture but if they are beyond repair there are things you can do to retain elements of the original.

1)You can obviously repair what is there.

2) You can indeed place double glazed units into wooden frames. It depends on the rebate that exists though. A company experienced in this would be vital.

2)If beyond repair and decide on UPVC, why not get a company to encapsulate the existing leaded light top sections between double glazing. This is a nice way of giving a nod to the original design.

4)More expensive: New timber frames with d/g units and encapsulated top lights.

You can also save a lot of money by renovating what you have rather than replacing what is there.

For example; why not spruce up that front door rather than replace it with an awful composite or upvc door (which will probably only last 15 years before the internal mechanisms break or somthing....

Would you rather this:

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Or this:

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Once the door is renovated all you would need to do is apply a decent amount of draft proofing which you can buy at a diy store for less than £20.

Sorry about my rant......

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