Bay window wall coming away from main house wall

[adm]

I am wondering if anyone has any ideas regarding a problem my daughter has with her bay window wall.
The external wall under the bay window is pebble dashed with a stone cill sitting on top then a upvc double glazed unit sitting on top of this, where the protruding bay wall meets the main house wall it is cracked vertically down both sides and it seems to be getting worse as the years go on, and when you push against the cill you can feel movement. The house is a terraced house in the middle of the street which was built in the 1900. She has had a couple of builders round to call and one said the wall just needs rebuilding and tying back into the main structure quoting £550 + vat where as another builder has quoted ( verbally ) anything up to £3000 + vat as he says the wall is sinking and needs better foundations laying and having to take the window out before anything can be done with the wall. She is going to contact her insurers in the morning but i was just wondering if anyone had any ideas ( is it subsidence ? ) and also of the different oppinions and quotes of the builders ?
Sorry about the length of the post but their was no way of condensing it. Any help and advice would be most greatful.

 

[stuart45]

Quite a common problem as builders at the time thought that bays didn't need much of a foundation.

 

[adm]

Thanks for your reply Stuart45, so in your oppinion do you think the second builder is correct and what about his quote ?
Also is this through subsidence and do you think it is wise to contact the insurers ?

 

[stuart45]

It's worth trying your insurers as they can only say no. Technically it's differential settlement rather than subsidence which is movement not caused by uneven loads of the building, but by something like a mine shaft or ground washed away by a leaking drain.
The second builder is going to do a better job as the cause is likely to be an inadequate foundation. I wouldn't like to comment on the cost without seeing the job, but £3,000 doesn't go too far in the building trade.
I have known people just have the brickwork rebuilt, but there is no way to be sure of how long it will last.

 

[^woody^]

You don't want to be getting any builders involved until you know exactly what is going on with the bay.

Every builder is going to give you his take on it, but you need to know what has caused the movement, whether it is progressive and then what the most appropriate remedial work is

It's no good tying the bay if the foundation is moving. And is no good rebuilding the bay if the issue is with the main house

You need it looked at properly by someone qualified to comment, and appropriate work specified - if any actually needs doing.

If there are no major cracks on the inside then it's not really an issue. And then for external cracks, unless you can get your fingers comfortably in them, then they can wait and could just be filled with some mastic to keep the water out.

But the first step is to have it properly assessed. The insurers may comment, but they wont be truly independent will they. So your daughter may be better off spending a couple of hundred pounds on a report.

 

[Symptoms]

adm - check-out the bays in the rest of the terrace to see if it's a common problem - this may give a hint about footing problems. Whilst we all value the 'safety net' provided by our insurers calling them-in comes with a risk that the property will be 'branded' as having structural issues and WILL cause problems when it's time to re-insure (with another company) or when selling the house. Getting some independent advice from a Structural Surveyor first maybe might be wise (yep, you'll have to pay) then if the problem is serious (or expensive to fix) you'll have to contact insurers. If the job is more than filling small cracks with mastic (DIY) to keep it weather-tight don't go directly to a builder ... surveyor, insurers then builders is the way. If money is tight and you can't afford a survey (a couple of hundred quid perhaps??? - ring a couple up to get an eastimate before you instruct them) - then perhaps contacting the insurers is the only option.

How big are these gaps? Remember the bay's been messed with since it was built; pebble dashed, say in the 30's, original windows ripped-out and plakka ones put in. If the gaps are small but unsightly consider mastic with pebbles pushed into the surface match (gather some pebbles from elsewhere on the walls by brushing a few loose ones off ... these old pebbles will match).

 

[adm]

Thanks for all your replys they are most appreciated, i have walked up and down the street looking at all the bays and i can not see any that are cracked or look as though they are pulling away from the main structure of the house as my daughters is. So why is this happening to my daughters ? There are no internal cracks at all and as far as i can gather after looking through archives of the area their were no mines of any kind in the area and there are no drains near by except the gutter where the rain water runs along the side of the road. The gaps are about at most 5mm wide but as i have said to me its as if the bay wall is falling forward from main structure.

 

[stuart45]

Are the cracks wider at the top? 5mm isn't too serious although it will allow rainwater in. You may find that the movement stops in time.

 

[adm]

Thanks again for the replies, the cracks are 5mm at their widest point which is at the top of the wall under the bay going to a hairline crack where the wall meets the pavement.

 

[adm]

After reading all replys we have decided to bite the bullet and have a structual engineer call to asses the cracks we have been quoted £150 + vat so not too bad and then at least we will know one way or another whether the cracks are serious or not.
One further point i would just like to know out of curiosity before he does come ( Friday ) is that if as one of the replys i have had if it is differential settlement what will this entail she is expecting having to have wall demolished and rebuilt but will she need to have some sort of underpinning done and deeper and stronger foundations laid ?

 

[^woody^]

It all depends on what is causing the movement and if it is progressive.

Underpinning the bay will be the norm if it is progressive.

A recent repair method is to stabilise the ground by injecting polyurethane resin grout into it, which can even lift the wall back up and causes no disruption. But I don't know how effective this is in practice. I see quite a few adverts for it, with claims of insurers recommendation. But who knows

 

[stuart45]

If the Engineer decides that the foundation is inadequate, then after the bay wall is demolished a deeper foundation can be put in. Is it a cavity or solid wall?

 

[adm]

The wall is a solid wall but what i dont understand is if the foundation is inadequate why are none of the other houses in the street, not even the next door neighbours either side suffering the same problem as i have said it is a terraced street so i would presume all the foundations of each hose being the same.

 

[^woody^]

Because every single property is different, and every patch of ground is different, and every property is built built differently.

So some crack, and some don't

 

[stuart45]

You will often find with bays on old terraced houses that the foundations were just dug out at random depths, usually much less than the house walls. The brickwork on the bays was not always tied in to the main walls properly, depending on which bricklayer was building it.
Your house could also be the first of many to start cracking. Nowadays the extra traffic on the roads can cause cracking where previously the odd horse and cart did little damage.