Bay window subsidence vs whole house subsidence

Jeezz

I've notice big cracks on both internal and external of my bay window. It is also on both sides of the window itself and looks like it is pulling away. On on wall where there is a chimney breast the wall is detached from the ceiling 'skirtings'.

I had a builder in to update a kitchen and he suggested it was just the bay window and that all it needed as cement poured to prop it up.

I'm thinking i need to get insurance involved to get the full building assessed in case it's a bigger problem, but I'm trying to weigh up the costs. Ie: insurance excess is £1,000, or get a chartered surveyor independently as if it is only bay window then it'll likely be cheaper to resolve with involving the insurance company. But I've also read that if not done properly it could cause more issues further down the line.

Doozergirl

It's pretty common for only the bay window to move because they were built with even less foundations than house itself, making them most vulnerable.  What you get is differential movement.  

I am inclined to agree with the builder.  Unless there's signs of a wider issue that you haven't mentioned, I'd deal with the bay and not open the insurance can of worms. 

GDB2222

They don’t look like huge cracks to me. You could start off by monitoring the cracks, to see whether they get worse.  We had a particularly dry summer and, if you’re on clay, the soil may have shrunk a bit. The cracks may close up as the soil rehydrates in winter. 

I am not sure what your builder is planning, but I think that you would need a fair bit of concrete to make any difference. Does he have a lot of experience of this sort of work? 

Rishi2020

I would speak to a structural engineer first, it would be a cost but you'll know exactly what to do after.

stuart45

Have you got any external photos?

Silvertabby

Doozergirl said:

It's pretty common for only the bay window to move because they were built with even less foundations than house itself, making them most vulnerable.  What you get is differential movement.  

I am inclined to agree with the builder.  Unless there's signs of a wider issue that you haven't mentioned, I'd deal with the bay and not open the insurance can of worms. 

Does that depend on the age of the house?  We bought ours as a new build in the early 1990s, and first saw our property at foundation level - and the (square) bay was definitely part of the whole foundations, not just an add-on.  

stuart45

It's especially Victorian bays that seem to have this problem.
On more modern sites, the digger takes out bays and chimneys to the same depth. After 1976, the foundation depths were increased a fair bit.
1990 would normally have a substantial foundation.

Section62

Silvertabby said:

Doozergirl said:

It's pretty common for only the bay window to move because they were built with even less foundations than house itself, making them most vulnerable.  What you get is differential movement.  

I am inclined to agree with the builder.  Unless there's signs of a wider issue that you haven't mentioned, I'd deal with the bay and not open the insurance can of worms. 

Does that depend on the age of the house?  We bought ours as a new build in the early 1990s, and first saw our property at foundation level - and the (square) bay was definitely part of the whole foundations, not just an add-on.  

Yes, as stuart45 says, more recently built properties shouldn't have this problem as the issues of differential movement were better understood.  Anything up to about the late 1960's is potentially affected.  Older properties more so because their foundations are typically less robust overall.

Section62

Jeezz said:

I had a builder in to update a kitchen and he suggested it was just the bay window and that all it needed as cement poured to prop it up.

What exactly did he mean by "cement poured to prop it up"?

If the bay is moving due to ineffective foundations then it will need underpinning - which will involve placing concrete, but is a bit more nuanced than just pouring concrete somewhere and hoping for the best.

The starting point should be digging a trial hole to confirm the foundation type/depth of both the house and the bay.

diystarter7

Silvertabby said:

Doozergirl said:

It's pretty common for only the bay window to move because they were built with even less foundations than house itself, making them most vulnerable.  What you get is differential movement.  

I am inclined to agree with the builder.  Unless there's signs of a wider issue that you haven't mentioned, I'd deal with the bay and not open the insurance can of worms. 

Does that depend on the age of the house?  We bought ours as a new build in the early 1990s, and first saw our property at foundation level - and the (square) bay was definitely part of the whole foundations, not just an add-on.  

Hi

Very true indeed,

What can happen I guess is that foundations are only as good as the people that built them. I too have noted houses with actually square bays built around 100 years ago or so having some evidence of movement. These houses I think hardly had any proper foundations as we know them these days

I'm guess that around the bays in older houses andsome 1930's houses for whatever reason they built less durable foundations and this is why youn can often see cracks big and hairlines - I cant think of anything else other than they are more exposed I guess as the stocil out and crack at a joint just like older, terraced up and over houses cracking and the point where the house becomes more narrow - of the case on london's  clay soil.

If that was my house, I'd initially seek the opinions of a couple of builders and then a buildings engineer that was local to the area and has been established for a while as thye often know if it is a common problem etc. Then decide your next steps

Good luck

Thanks

stuart45

The brickwork on a square angled bay gets a much better tie into the main walls than a squint angled one.