Bay Window Cracks

[newrick1962]

Had some windows replaced recently and I now have some cracks from both bottom corners of the upstairs bay window going straight downwards.
There's a draft coming through and we can hear traffic noise too.

The background to this was the bedroom wall had suffered some damp and we believed the old window was the cause. However I'm thinking that the wall was probably weak to begin with and replacing this window has caused it to move. The downstairs window was also replaced but there doesn't appear to be any problem with that.

I now suspect the damp may have been coming from the edges of the rendering that covers only the bay and no further.

So, I'd appreciate any views on what to do about it?

Many thanks

Russ

Untitled

• newrick1962
• 7 Dec 2012
• 1

Untitled

• newrick1962
• 7 Dec 2012
• 1

Untitled

• newrick1962
• 7 Dec 2012
• 1

 

[jeds]

Could be a number of things. The worst case (presuming the old window was timber frame with probably some fairly heavy timbers mullions) is that the old window was supporting the panel and window above and possibly the bay roof. The new window being a pi**y ass uPVC job isn't capable of the same support. This all depends on the method of construction of the bay. There are several possible configurations. Does the new window have any load bearing posts in it? Maybe ask the fitters to comment.

 

[newrick1962]

Don't know about load bearing posts but I can tell you the previous window was an old UPVC window.

Had a closer look at it since I posted I think the sill on the inside (which was not replaced) has moved and may be the cause of the cracking inside. Might be worth a wait and see what happens approach.

I do think the rendering on the outside needs, at least temporarily, to be sealed at the edges because there is a definite gap on each side.
Would silicone be appropriate?
Might give me some breathing space before getting it re-rendered outside.
Then we'll see what's underneath.

 

[dann09]

1. As you say , there are gaps at the edge of the rendered panel, and some damage centre low. Are any hairline cracks or slight bulges present?
If you grip the upper Pvc frame, and attempt to gently move it in or out, does it budge?

2. Has your upper Pvc framing, perhaps been forced into the space between the upper cill and the eaves soffit?
You also have two fully opening sashes, upper, and two top opening lights only, lower. This might have some bearing on the problem.
Do all open and lock freely?

3.Water damage is not the culprit, such cracking is pressure cracking.
As jeds says, originally, before any Pvc, there would have been hefty wood mullions - check un-modernised, similar properties in your rd/area.

4. It's not unknown for frame fitters to, if possible, spread the building opening to force their frames into the opening.
Perhaps there's no adequate lintel at the eave/wallplate and roof pressure is bearing down.

FWIW, after reviewing the above i'd guess that the middle, rendered studwork has been forced from its side fixings by a combination of the above.

 

[tony1851]

The rendered part between lower and upper windows could well be just a 'brick-on-edge' wall, lightly reinforced with thin timber uprights, and then plastered internally and rendered externally.
The timber uprights would have been nailed to the top of the original lower frame, and to the cill of the upper frame. Once you replace the frames, these flimsy walls often give trouble.
Just do a temporary fix and keep an eye on it for the time being.

 

[theoldun]

Our eyes are not so young now, but it would appear that the two cracks are in the internal wall each side of the ground floor bay, running from the cill down towards the skirting, and has been caused by slight movement due to lack of correct tie between main wall and bay brickwork.
If this is the case, then either open crack out and fill, or cut crack back 100mm wide to brickwork, stick 75mm wide exmet in, render in sand and cement, set in thistle or multi.
You have crack all round head of ground floor window, but at a guess would say this is where the window fitters have made good.
The cracks have nothing to do with lack of support poles on windows or spandrel wall panel between windows.
In passing looks like condensation inside.
Are we right, or wrong Tony?
Regards oldun

 

[^woody^]

Those are rotational cracks. The outermost edge of the bay is moving down, not out.

Assuming that the bottom bay is not moving ....

Either the fitters have not adequately propped the bay during installation, not packed the bay for future support, or the frame mullions are not giving structural support.

The new frame can be checked for distress at the top and bottom of the mullions

If the frame is not providing structural support, then that needs addressing - replacement.

If the frame is load bearing, and there is just some movement which is now being supported by the frame, then the bay should be strapped back internally. But only if/when movement has stopped.

 

[tony1851]

Are we right, or wrong Tony?

Right as always

 

[newrick1962]

TheOldun
Thank you for your reply, it is appreciated but I need to clarify to you that the cracks in the internal walls are on the first floor. The ground floor is in perfect shape.
Does this change your opinion in any way?

 

[tony1851]

Ideally, you need to remove the plaster from the bay wall upstairs to see how, if at all, the curved wall is fixed to the main brickwork walls each side. Until you know this, anything else is just guesswork.

 

[newrick1962]

Yes, we have a plasterer lined up to take a look at it so I'll know more when he gets around to us.
Thanks to everyone for the help so far, gives me something to talk to him about.
I'll post more after he's had a look.

 

[dann09]

You dont need a plasterer to investigate possible structural conditions.

Remove generous amounts of plaster, at all "crack" areas, as tony recommended, and post pics on here.

 

[DIYedboy]

Regarding your 'damp' as a previous poster has said.......it's condensation, 1930's house bay windows had a 9" bay wall downstairs and a 4" wall upstairs, if this bay faces North you'll always have condensation in the winter and this will always lead to black mildew. You will have to thermal line the bay, extend the window board and ensure you have a vapour barrier to stop interstitial condensation, or wipe the wall with a bleach and water solution every two months during winter.

All the 30's bay window houses I've had had cracks where the bay met the wall, it's worrying but a bit more polyfilla when redecorating covers up the problem temporarily. Tile hung bays are the best cos they can hide a load of movement without any telltale cracks outside!