Advice on how to proceed - possible drains collapse under house

[Ellie78]

Posting on here, hoping it's the right place- perhaps people can recommend the way forward for us. This must have happened to others in this area! Not just us...

We own a basement flat, tenanted now, but we are hoping in the next couple of years to renovate it (it's OLD) and stick it together with the one we currently live in upstairs.

To cut long story...etc.

Our tenant moved in in September and in December started reporting water coming in on the party wall side (ie. not near external wall) at the back of the flat, every time it rained. We had a succession of plumbers in, who all said it couldn't be anything else but water coming down the party wall (even though no damp upstairs), we got a roofer in who (to be fair to him) was doubtful but informed us we had no coping stones; we replaced coping stones and still the problem persisted....we have since employed a surveyor who narrowed it down to two things....including the drains...and on further investigation it's looking like...it's the drains, as we managed to produce the water coming through on a dry day, by shoving a ton of water down the drain.

I'm about to go down the route of getting drains companies in to quote us for the investigation work - ie. a camera down there to establish what we're dealing with...but I just want to be prepared. It must be a significant collapse - the water is obviously rising underneath the house and being pushed though into the basement - I don't see this happening with a small crack. This drain carries the water from our guttering but also from the 2 kitchens of our and upstairs flat...it probably goes very deep.

I would really appreciate some advice from someone who has been through this or knows about it. What should I ask the drains company? How would I check whether this might be causing subsidence - presumably it's just grim underneath - should I be worried about that? If it's under the party wall, which it might be because that's where the water is coming from, then it is also next door's problem - how do I ascertain whether that's the case?

And insurance apparently doesn't cover fixing the drain, though it might cover investigation of the problem - I wonder whether (if it comes to having to dig up the flat) we can sell that as investigative.... We're in it together with upstairs (as freeholders) but we still are going to take the burden of it as majority freeholders. And why on earth did I want to own a property again?

[Ellie78]

thnks for pms

would really appreciate reliable drains investigation company recommendations from anyone out there.

[monica]

I have you tried Thameswater? We had a similar issue with our place. The drains had collapsed and we called Thames water to confirm how they collapsed, and if the problem was external to the property, so thames water/Southwark council responsibility.

All the contact numbers should be on the website.

Good Luck

[Primula]

Have you had the water tested to see if it is sewage? i.e. drain water. It could be the rising water table as a result of all the rain we have been having. I used to have a flat in Underhill Road with a basement that got flooded when there had been heavy rain. Eventually, I got it 'tanked' and this stopped it coming through.

[Ellie78]

Thanks! If the drains collapse is under your property I think (unfortunately) that is your problem,

Rising water table might have been it... But we managed to replicate the leak on a dry day. By pushing water through one of the drains.... Plus we're on a hill, which I guess doesn't rule water table factors out... Also it hasn't done this before, and the previous tenant has been there for 11 years- the leak started before the really bad weather, in mid December.

Don't get me wrong. I don't want it to be the drains, but neither do I particularly want it to be rising water table,

[first mate]

If it's a shared drain between two properties, as is often the case with terraces in this area, then I think it is the responsibility of Thames Water because it counts as a public sewer, even though it is often at the back of the property. You need an old drainage map. These shared seweres used to be the responsiblity of the LA but a few years ago Thames took over. Perhaps your surveyor could shed more light on this as well as your property deeds.

[lizbells6]

If you are in a terrace, the drain is probably shared, as first mate said, usually in pairs, and TW is responsible for the shared part going under one of the houses. There should be an accessible rodding eye, small round drain cover, in alternate front gardens. It could be that the drain is just blocked and backing up, which was the problem when our basement kept flooding, even when it wasn't raining. Thames Water would definitely be my first call out, and if the drain is not going under your house, get them to check neighbours drains on both sides, not just the one you share with.

[nic32]

First thing to do is to find out if you share a drain wih either of your neighbours to the rear of the houses. If so Thames water are responsible for all works I think. It is called a Section 28

[Mustard]

You can get a copy of the drains plans from Southwark or relevant Council. They were drawn up when the houses were built. I have had to do this with two different properties.

[Ellie78]

Thanks mustard- lewisham planning and building control say they don't have them and are telling me to contact Thames water. :(

[Mustard]

Oh, strange, I did deal with Southwark both times. Surely they should have them on microfiche. What did Thames Water say?