Subsidence/extension pulling away from main building

[AnnettePW]

Not sure what to do in the situation we are in.
Our house which we bought in 2008 is probably 18th century although some of the timbers have been dated as 17th century. It is not listed because there have been many alterations to it over the years leaving very little that is original.
We had a full building survey costing over £1000 at the time and there were issues such as the unsuitable render which we have since remedied but no mention of subsidence or the 'modern' side extension.
The extension consists of a conservatory and bathroom. The roof of both is polycarbonate and there is a single skin block wall dividing the two rooms with a false ceiling in the bathroom side. Not sure when it was built but probably 1970's or 80's. The previous owners did not own up to building it but they said so many things that we have since found out to be untrue we simply don't know.
We had planned to install a new bathroom and starting taking off tiles to find cracks of about quarter of an inch in the wall of the small passageway which leads into the bathroom. At this point we contacted the insurance company who said it is subsidence caused by the downpipe from the roof of the extension not going into a proper soakaway. Since the process started small cracks that were hardly noticeable have become larger including ones upstairs on the landing. The insurance company said that if we installed a rainwater barrel the subsidence would stop. We have done this and, according to their measurements, it has stopped, however the cracks everywhere are getting worse and you can now see daylight through one of the ones in the bathroom. We really don't believe that the subsidence is caused solely by the rainwater issue - if it was why has it taken since the 1970's for it to cause subsidence? Also we are unconvinced that it won't move any more. The area is one where there is a high water table, other properties in the area are affected by subsidence and newer houses have been built taking this into account.
The insurance company say that they can carry out 'repairs' but of course this would mean like for like. The existing bathroom is pretty much in need of renewal and the conservatory is fairly awful, the roof in parrticular probably has very little mileage left in it, so we really can't see the point of them doing the repairs, reinstalling the bathroom fittings etc. tiles matched up, etc. for us to still be unhappy with it and rip it all out again some time in the future. Especially if there was then further subsidence.
They say that they think there is £15,000 worth of repairs there but have yet to come up with a cash settlement figures as an alternate. Would this be £15,000?
This would not cover the cost of demolition, repair to the main wall of the house and rebuilding a new extension.
Really not sure what to do. We certainly couldn't sell the house in the mess it is in. We have already spent around £70,000 on repairs and renovations to the house and don't have any more savings. We are retired and living on pensions so not wealthy.

 

[Gareth Hughes]

I'm just going to bump this up since new members' posts don't go to the top of the pile.
You do seem to be in a pickle and I wish I could offer some supportive words. But someone who has been in a similar situation should be along soon.

 

[Flyfisher]

I'm no expert but I can offer a few thoughts based on experience with our property, part of which is a gable wall that seems to be moving - although it is (we think) a C17 wall, so not a recent addition.

Firstly, I've had advice ranging from "don't worry about it" to "it needs drastic underpinning before it falls down". Well, we've been here for almost 10 years now and it hasn't fallen down yet and I believe the problem pre-dates us by many years, so I'm at the "don't worry about it" end of the spectrum. The wall itself used to have a large 'boiler house' attached to it, but this was demolished in the mid-80s. The roof purlins were not fixed into the gable wall in any way (not necessarily a problem). The roof had been leaking for many years before we took it on and this had been 'addressed' (in the 60s we believe) by fixing roofing sheets to the underside of the rafters. While this prevented any water entering the roof space, it merely diverted this water onto the top of the building walls and, being a 'rubble wall', percolating down through the wall weakening the lime mortar, which in places was almost like sand. Add to this a blocked soakaway resulting in the downpipe at the corner of the gable depositing all its rainwater at the base of the gable wall.

Thus, my feeling is that a wall that had been stable for a couple of hundred years or so suddenly found itself without the support of the 'boiler house', water percolating down the inside of the walls and regular flooding of the footings on which it stood. All this would undoubtedly have changed the equilibrium of the wall with the inevitable result that it has moved in order to find a new equilibrium - as evidenced by the cracks in the wall.

Soon after taking on the house, I relaid the roof and added a proper waterproof membrane, so water ingress is no longer a problem. While doing this, I added some steel fixings through the wall and onto the roof purlins, so if the wall continues to move it now has to 'pull' the roof with it (which may be a good or bad thing!). I've relaid the surface water drainage so there is no more flooding of the footings. Finally, this year I've added an oak-framed 'lean-to' roof against the gable wall, which should reinstate some of the original support of the old 'boiler house'. In short, I've done a number of things that will, again, change the equilibrium of the wall - hopefully in a stabilising way. Meanwhile, I've repointed all the cracks in the wall, some of which involved removing and rebuilding some sections of the wall around the cracks and am no longer worrying about it.

I mention all this, not so much as recommendations of how to fix your problems, but to illustrate that such problems can have multiple reasons behind them causing a gradual change to the building. As such, there is unlikely to be one quick and simple fix - short of demolishing and rebuilding from scratch. For example, I'd say the insurance company advice about adding a water butt to the downpipe is a good idea as far as it goes but, based on my experience of how quickly water butts can fill up in a downpour, I'd be questioning what happens to the overflow water? If it just spills over, then what's the point? I'd also want to examine the joint between the extension and the original building - is it properly watertight? Water washing down dirt and debris into any crack can create a sort of 'ratchet effect' whereby as the crack opens it is prevented from closing back up again, thus the slight natural seasonal movements of the building can be limited to one way only, which can cause problems. Coincidentally, this morning I've been fixing a similar sort of problem with the plastic guttering on some outbuildings. They naturally expand and contract depending on the temperature and in some places the gutter clips seem to only allow movement in one direction - another sort of 'ratchet effect' - with the result that the guttering pulls itself apart at one of the joints. Hopefully I've now fixed this with a few strategically placed stainless self-tapping screws to hold the affected joints together.

Without a lot more information and/or photos it's probably not possible to give any definitive answers, I just hope my ramblings might give some ideas about how to tackle these sort of problems - starting with "Don't Panic"

 

[AnnettePW]

Thank you for your observations. As far as we can see there is no gap between the old and new, the polycarbonate roof joins the wall of the main house with lead flashing so without taking this off you wouldn't know if there was a gap. The join on the side isn't visible either, it's covered with UVPC and sealed. However the door from the main house (dining room) into the conservatory section doesn't close indicating there is downward and possibly outward pressure on that wall. The side windows in the conservatory will open but are then almost impossible to close so something has moved but not sure exactly what. On the other side of the extension in joins on to another part of the house that is another modern extension. I think this may have a problem as well as we have replaced the door to the outside once already because it was warped and now the new door is starting not to close properly. Above the false ceiling in the bathroom there is a hole measuring about 10" and this is just above where the worst of the cracks (so far, the tiles might be hiding some more) are. The hole is in the wall that the extension is attached to and which would have been the outside wall of the house. The house consists of a main part (probably 17th century), another section (19th century) and about three other modern extensions all built at different times. I don't think its about to fall down but worried that if the insurance people do the repairs and when then put a new bathroom in, we'll just start getting cracks again. To demolish and rebuild we would also it seems need planning permission and having plans done is going to further increase the cost.

 

[MatthewC]

Annette

I really do sympathise with you about this. Like FF, I am not an expert (nor a lawyer), but I have done a lot of building work in the last few years. My first thought about the extension is whether any Planning , LBC or Building Regulations permissions were either required or granted? Can you find any records with the council, either on-line or by asking them? It really sounds to me as though the extension with a polycarbonate roof (!) was erected quickly and cheaply, and may have had none of those. If that is so, there's a very real chance that the foundations are negligible. Have you checked to see?

If you find that's the case then really the surveyor is at fault, as are whoever did your conveyancing, as this sort of issue should have been apparent. If they had spotted it, then you could have allowed for it... If indeed the surveyor is at fault, then HIS insurance should cover you for a proper rebuilding, I would think.

Best of luck

Matthew