Bay window drooping, any builders here?

cherryblossom123

Hi,

I am having some work done on my house. Prior to purchase the surveyor flagged the slope with the following recommendation

"There are cracks both sides of the bay and the floor has dropped slightly. This is usually caused by inadequate support when the bay window frames are replaced. On a single visit, it is difficult to confirm that this has ceased. If it continues to drop, then the bay studwork and floor will need to be strapped back to the house wall. Assume a budget in the region of £1500.00"

I felt the drop towards the bay window and after purchasing so it wasn't unexpected.

This is what the slope looks like from the outside, and on the second photo I have added a straight purple line and also applied similarly to the neighbours which doesn't appear to drop at all. In particular notice the red tiles going underneath the purple line on the second photo. You may need to zoom the photo to see it better but if you do it should be clear. Alternatively just consider the left hand window (when viewing from the street/left hand side of the photo) of my property vs my neighbour. On mine you can see the top left corner of that window clearly, but you cannot see the top right corner as it is obscured by the sloping window from the bay above, unlike my neighbours in which you can see both

The builder has been working on it today, to be honest I know next to nothing about building work, so apologies if I am not making much sense, I explained the drop and gave the above quote to my builder which is great.

He has been in today and explained to me what the plan was but I didn't fully understand (which is on me to be honest, the rest of the work I've had done is coming along nicely so no complaints!), at the moment the job is still in progress and it looks like this:

I'm unsure if we are expecting anything further to be added in terms of support or if the two pillars will just be removed.

My questions are:

1) Are these metal poles that installed at the moment just pushing the floorboards up where they had dropped before the bay window or is this solution looking like it would actually raise the entire bay window structure. The builder mentioned something about joists and bracing, but I'm not sure to be fair (again that's on me). My concern is that if it just makes the floor level in the room with the bay window it could be okay now but get worse over time? I'd prefer the whole structure to be sound - and to be fair it may be fine already and that the metal poles can just push the floor boards flat, in which case maybe a solution like this is okay. Or perhaps this will actually raise the whole structure, I genuinely don't know.

2) The floor of the room with the bay window is more straight now (not perfect yet, but better for definite), with less of a drop/noticeable sagging/drooping into the bay window, I'm assuming this is as a result of the metal poles and whatever else they have added to prop the floor boards up. However looking from the outside of the property, the red tiles are still completely the same as before, with the downward sloping angle that can be seen in the second photo. I'm not sure even if the bay window is lifted and supported properly whether those tiles will still be at that sloping angle. I suppose it doesn't matter if it is just cosmetic, and the room floor is flat and the bay window is supported fully (I was hoping to put some seating next to/possibly in the bay window). In future I had planned to replace those red tiles and maybe get something a little less tired looking. for example something like this:

Will that be able to be done without having the sloping angle on it. I guess I'm asking is the sloping of the red tiles caused by the drooping bay window and if the bay window is fixed (as the builder is doing now) would we expect those tiles to also straighten out.

3) If the metal poles are just pushing up the floorboard of the room above to make the floor straight there, should the outside also be raised up somehow and supported?

I've been told this is a fairly common problem, and nothing to worry about, but I'm a bit over cautious/paranoid as it is my first home, and as I say I wanted to place some seating in the bay window and replace the tiles eventually. Oh and another thing I didn't notice the downstairs ceiling show any drooping or sloping, but the lower window is a bit hard to open and shut, I wonder if it could be related, having said that there are 2 windows that open one on top of the other and the top one opens fine, so perhaps that is something else.

I want to ensure that a) the floor is flat in the bedroom, b) the bay window is secure and feels secure (no feeling like walking in that area is going to damage anything or exacerbate some existing problem, c) the tiling on the front of the property can be completed in future and not have it sag like it currently is. I want it to be exactly like the neighbour were a straight line can be drawn without the tiles going off at an angle.

I hope all my questions make sense.

TELLIT01

The props are to stop the floor above, along with the bay and the roof above that collapsing completely.  What appears to have happened, and it's surprisingly common, is that the previous timber windows were strong enough to support the floor above without additional support.  uPVC windows have very little structural strength and the builder will need to add some sort of solid framework to support the upper floor, bay and roof.

Albermarle

TELLIT01 said:

The props are to stop the floor above, along with the bay and the roof above that collapsing completely.  What appears to have happened, and it's surprisingly common, is that the previous timber windows were strong enough to support the floor above without additional support.  uPVC windows have very little structural strength and the builder will need to add some sort of solid framework to support the upper floor, bay and roof.

Having some knowledge of uPVC and its use in window frames, I can say it does have pretty good physical strength. The uPVC is used ( as opposed to other plastics) for its inherent stiffness, and in large windows is often reinforced with a metal insert.
The point is more that does it have enough strength to hold up a structural wall/floor? Probably not, but I am not really sure that a wood window would have done either.
So I am never quite sure about this theory that the timber window itself was supporting things before, and the UPVC not afterwards.
Maybe something else was changed during the installation?

stuart45

The builders will probably be fitting bay poles jacks. These are now required when fitting plastic bay windows which don't have the strength of the old timber ones. This is a common problem when timber windows are replaced with plastic. It's even worse when there's masonry above.

TELLIT01

@Albermarle if you saw the dip over ground floor windows in the housing estate my mother lived in after uPVC windows had been installed,I suspect you would have less doubt about the comparative ability of timber and uPVC to support the load above.  There was a very noticable deflection in virtually every house within a year or so of windows being replaced.  I think it unlikely that anything else was changed during installation in every case.

casper_gutman

Albermarle said:

... I am not really sure that a wood window would have done either.

I'm entirely sure that a suitably designed timber frame can hold a structural wall/floor. There are timber framed houses all over the world where the whole house is held up by nothing else. The issue isn't necessarily that one material is being swapped for another, it's that framed structures with window inserts are being replaced with windows that lack any structural elements, without considering how the modified structure will stand up.

Quite possibly a uPVC structure could be made which would do the job. Certainly some kind of reinforced polymer composite could do it. But too often the installers of replacement windows don't even think about structural requirements.

Albermarle

casper_gutman said:

Albermarle said:

... I am not really sure that a wood window would have done either.

I'm entirely sure that a suitably designed timber frame can hold a structural wall/floor. There are timber framed houses all over the world where the whole house is held up by nothing else. The issue isn't necessarily that one material is being swapped for another, it's that framed structures with window inserts are being replaced with windows that lack any structural elements, without considering how the modified structure will stand up.

Quite possibly a uPVC structure could be made which would do the job. Certainly some kind of reinforced polymer composite could do it. But too often the installers of replacement windows don't even think about structural requirements.

Thanks, that explains the difference better than just comparing uPVC and wood like for like.

stuart45

Modern Upvc bay windows have bay jacks and poles. On new builds there's specially designed lintels nowadays that will take a cavity wall over the top.

Section62

Albermarle said:

casper_gutman said:

Albermarle said:

... I am not really sure that a wood window would have done either.

I'm entirely sure that a suitably designed timber frame can hold a structural wall/floor. There are timber framed houses all over the world where the whole house is held up by nothing else. The issue isn't necessarily that one material is being swapped for another, it's that framed structures with window inserts are being replaced with windows that lack any structural elements, without considering how the modified structure will stand up.

Quite possibly a uPVC structure could be made which would do the job. Certainly some kind of reinforced polymer composite could do it. But too often the installers of replacement windows don't even think about structural requirements.

Thanks, that explains the difference better than just comparing uPVC and wood like for like.

IIRC one of the issues with uPVC is that it is subject to creep under loading.... over time it will allow movement that you don't get with timber.  Likewise uPVC underground drainage pipes will deform over time if not properly supported at the sides and invert, whereas VC/CI doesn't.

Timber is good under compression - which is what the window jambs may be experiencing.  Sections not that much larger than older window jambs were used as pit props in Victorian mines... with the expectation they could be supporting loads perhaps thousands of times greater than you'd expect from the typical bay window structure.

Albermarle

IIRC one of the issues with uPVC is that it is subject to creep under loading
 Likewise uPVC underground drainage pipes will deform over time 

Part of the problem is that they are made to a price point. Especially drainage pipes where margins are very thin and the polymer is the major cost factor.