Cellar tanking

[DeusEx]

Hello!

Just wanted to get a sense check please if anyone has experience of this?

We live in a converted Victorian terrace in London and, unsurprisingly, there is damp in the cellar. It isn’t huge - very much a storage space rather than an extra room - be currently isn’t much good for anything!

I’ve had a quote from a property company for c.£6k to tank it using sump and pump, plus plastering afterwards. This doesn’t include painting.

How does this sound - reasonable? Also, how much space do you lose through tanking - I’ve seen a few pictures and I worry it will take away quite a lot of space?

Thanks!

£6k sounds very cheap. The loss of space probably depends on the system used. I think you would need to ask the company that question. I doubt the cavity needs to be wide.

I agree, £6k sounds incredibly cheap, especially to include the sump and pump.

It's a while since I had my cellar tanked, but I would estimate I lost about 50mm on each wall.

If the space isn't really usable currently then for that price then do it, even with some space lost it will be worth it.

6k! Friend recently had theirs tanked (nothing fancy) and it cost over 20k. Tup North, too.

people most often say "tanking" to mean painting a proofing compound on the walls. It is liable to be pushed off by water pressure if the walls are underground, unless applied to the outside of the wall. It's the cheapest method.

Some people mean applying waterproof lathing to the wall, which has a drainage gap or channels so that water can run down in the gap without entering the room. It then enters a gap under a false floor or drainage tiles, which also have a gap so water can run into a sump, that either runs downhill to a drain, or is automatically pumped out. This is current practice for basements and underground structures, and is much more satisfactory. An internal wall can be built on the dry side of the lining, or some of them can be rendered or plastered. It is much more satisfactory.

Because UK homes rarely have basements, builders are not very familiar with the techniques, but in some European countries they are very common so the materials and systems are readily available and understood, and are also imported to UK.

If the cost of doing it properly is too much, you can often get a Victorian cellar reasonably dry by stripping the walls of plaster and adding lots of ventilation. If the water evaporates off the walls faster than it soaks through, and if the ventilation sucks away the water vapour faster than it forms, the cellar will be OK. Often a new concrete floor with DPM needs to be laid, if there is a cobbled or bare earth floor it can be dug out to improve headroom a bit. You should not dig below the start of the footings except in individual small bays which are each concreted before starting the next one. Experienced builders will know this. Repair and repoint the brickwork if in poor condition.

IIRC Kingspan offer basement lining systems and will have diagrams and installation instruction on their website.

This is a pretty good illustration of how mine was tanked:

www.dampproofinghastings.co.uk/basement-tanking-using-damp-proof-membrane/

Oh gosh this is lots of choices :( collective view then that these guys may be too good to be true / there will be hidden costs?

That website has somewhat overwhelmed me!