FTB: Potential subsidence, certificates and drains

SilentSteve

We’re FTB and got our building survey back last week. The house is a 3 bed detached, was built in the 1970s and had a single story extension added to the back sometime before 2000, which is up to/possibly over the shared foul sewer (shared with the neighbours). The current owners amongst other things replaced the extension’s flat roof with a tiled gabled roof and put in French Windows in 2004. They don’t have a completion certificate.

The house is done up to show home standards inside which swayed my OH.

The house is on a sloping site and damp course at the back is ~1m above patio level, which in turn is ~0.5m above ground level.

When viewing the house I noticed hairline cracks inside below the joist supporting the extension’s opening into the house. Fair enough, extensions settle.

The surveyor has noted these cracks appear externally and called it longstanding settlement and differential movement where the extension joins the house. They run the full height and are wider at the top. He picked up there’s been previous repairs internally and externally, and says some are recent. To me looks like the extension wasn’t keyed in properly. Am asking for dates but know that internal d!cor was repaired in the last 5 years.

Additionally (and to me more concerning) is a diagonal crack in the brickwork in the side of this extension, which the surveyor said pointed to subsidence/foundation movement. In this case the crack has been repaired with new mortar (trying to get a date), and opened up again to 1-3 mm, the vertical cracks much wider than the horizontal ones.

There are no trees nearby, the windows in the extension operate freely, and the window boards are level, so it seems to be localised to this wall. The house stands on chalk not clay. Looking on the online building control register the house 3 doors along had its rear extension underpinned 25 years ago.

More recently a foul drain has been added down the side of the house for a new en suite which connects into the sewer behind the house. There are no manholes/inspection hatches (and no building control sign-off it appears) and we are asking for details.

The surveyor has recommended a structural survey and drain survey if we want to know more what’s going on. It’s more money and the mention of the “Subsidence” word has sown doubts if taking it on is a wise move (and how we’d get insurance if we think it may be present). But it’s a house and gets us out of renting.

It’s not a forever house for us, more 5-7 years so we want to be able to resell it. Additionally, the lack of completion certificates for any work done in the last 15 years (including a 2-story extension) gives us doubts about the quality of the work (e.g. the conservatory built over the sewer manhole which has no internal door). It’s all standing though, not going to fall down.

I also don't expect a structural engineer to tell us anything without doing some excavations, which the sellers will be deeply unhappy about.

Our solicitor is asking for proof that building control were involved, and I’m asking for dates and details of work.

Having spent too long thinking about it, I wanted to ask if there’s anything else I should do, and for impartial thoughts. I don’t want to be one of those FTB’s who run scared. Neither do I want to end up with a turkey.

Thanks for reading this long post! :T

ProDave

Lots of issues.

I would suspect that due to the sloping site, the extension would have needed very deep foundations, or possibly even piles. You start off saying single storey extension and later say 2 storey. Did they add an extra floor on top?

I suspect worst case is extension needs underpinning. Perhaps get an estimate for that and re negotiate the price?

Wait for then answers re building control but it sounds like a lot of it was done without.

SilentSteve

ProDave wrote: »

You start off saying single storey extension and later say 2 storey. Did they add an extra floor on top?

My bad, the two storey extension was done to the front of the house in 2004 (extending the whole front forward), at the same time they put the gabled roof on the older pre-existing single storey extension at the back.

The two storey extension is one of those where there's no visible internal joist where the old front wall was. Apparently BC visited for the foundations, structural beams and roofing for the 2 storey front extension, but no completion certificate and no proof of visits (yet).

Thanks for your input, great suggestions.

lincroft1710

I would just find somewhere else which does not have all the hassle.

SilentSteve

Final update: vendor agreed to get building completion signed off for one extension, but refused to discuss the others or answer any further questions about the property, e.g. when the subsidence cracks were last repaired or if permission had been obtained from the public sewer owner to build over/make a new connection earlier this year (as our solicitor could find none).

Back looking.