extension pulling away

xt40

I have a 1.5 story extension built on a raft which has been pulling away from the house for 3 years now since it was built. i know this as ive filled up the cracks (>5mm) a number of times and they keep coming back . id say its moved about 25mm at the top so far and im starting to get very p-ed off with it. the builder was/is a neighbour who should have been well aware of the soil conditions. i mentioned it to the builder a couple of times in passing and he said it would take a while to settle. to me though, it is more than settlement
i rang a piling contractor for advice and he said that where i am , you could be going down forever before you hit anything solid . he advised digging holes under the outer edge (in stages) and pouring concrete in under the edge of the raft to spread the load and give additional support.
i dont feel i should have to pay for this remedial work as we paid a lot of money for the job. i also dont want to claim off my insurance.
before i approach the builder and request that he sort it out, i thiought id post on here to see if anyone had any previous experience of this sort of thing.
i suspect the builder might claim that he is skint and cannot afford to pay for the repairs. would he have some sort of insurance himself that might cover it.
as he's a neighbour, I dont want to go down any legal routes but if he wont help, what are my other options.
thanks

Buford T Justice

Yes, he would have insurance that will cover this sort of thing.

Get a structural engineer out to have a look at it and they will tell you what the story is.

spida

Hi, I'm no use with the insurance/legal/construction etc. but just thought you may like to see a Channel 4 program I saw about a week ago which was about the Exact same problem as you are having. You can check it out on 4oD. They had other problems too that I hope you don't have anything like!

What they did roughly was to get a machine to drill a small bore hold down to the bottom of what turned out to be a filled-in river-course that their house had been built on. The house had been built on piles but the extension hadn't. So it basically was falling off the house as it was unsupported. When they found that the river-bed was 6m down they got a quote for some number of thousands of sterling (south of 10 but you'll hear it on the program if you watch it). Their insurance company decided they would pay (home insurance) but would like to see it happen first so they decorated the house and extension and left an easy-fill gap between the plastering of the house and the extension.

Anyway, I'm only giving you what I remember. Watch and you may pick up something. It's in the Uk so laws/costs etc. will differ but...