To tank a basement or not...

[neverwakeasleepingbaby]

Hi all, first ever thread so bear with!

I live in an old terrace townhouse (also a listed building, around 200 years old).

It has a basement which has the same floor plan as upstairs. It has two main rooms and a couple of "stores". It has a front door and window at the front, and a door with a light well at the back that I think used to have steps leading to the garden, but now it's just a light well with a grate in the patio (if you see what I mean?). So there is ventilation to the outside world at the front and back.

We would love to make this into a study and utility room. We have a planning/listed building application in at the moment and we've received positive feedback so we think it will be granted.

My neighbour has submitted comments to the effect that her foundations will be damaged if we tank the basement. She thinks that we should add a ventilation system instead.

I'm worried that it will not be usable as a study if we do that.

I'm open minded about what to do but obviously it might be a compromise.

What is the Mumsnet wisdom? Thanks so much!

How does your neighbour know that this will damage her foundations? What does your architect say in regards to this?

Thanks so much for replying. She has done a lot of research online in respect of what to do with her own basement. But it's all a bit "alternative" if you see what I mean. Not high quality sources, a lot of random men talking on YouTube about it.

Architect isn't worried about her comments affecting the council's decision.

I think there are two issues I'm concerned about. Obviously I want to do the right thing for the house and not damage it (or the neighbour's) in any way.
I also don't want to fall out with her over it. I think she feels pretty strongly about it, but as I say, I'm open minded so wondering if she does have a point!

I should also say that the architect has just said something like "English heritage have guidance on these things" but has been a bit vague so far. We haven't got into the details of what system to use or anything like that

From what I understand, tanking has become popular because its easy to do but it's not great for really old houses. I'm debating what to do with mine eventually - I know it isn't great for the old bricks in my basement but my neighbours have had it done so I'm not sure it makes much difference having mine done as well. I'm struggling to find any definitive answers so will watch this thread with interest

Don’t tank a 200 year old house!

Why? Tons of very old houses in London have had their basements dug out, what harm is it doing?

I think the concern is that, if you tank your basement then damp can no longer get into your bricks. which means there is more damp around in the soil that might go into her basement bricks and foundations. this is particularly a concern in bits of London where there are underground streams etc.

your architect should be able to put together some documents / guidance to reassure her.

Is there an alternative so it's habitable? Or is it forever destined to be a damp dumping ground?

Just to add as well, we don't want to dig down any further or knock any walls down. The floor plan and head height are fine. It's a basement rather than a storage cellar. We just want to make it habitable.

Is your basement damp at all/do you ever get little puddles? I've heard you're not supposed to tank cellars that are below ground because it forces the water up into the house. Our house has no damp but a damp cellar, next door have tanked theirs (it's a lovely extra room!) but have damp in their house.

Oh right that's interesting (and worrying I guess). No, we don't have damp in the house really at all. It's surprisingly dry. I think all the draughty sash windows help ventilate it!

The basement isn't wet as such - there are no puddles and it doesn't ever flood. We can happily store things on the floor. It does have some old plaster on the walls which is falling off, so the walls themselves are damp, but maybe if we removed all of that then the problem wouldn't be so bad. So hard to know what to do!

Just wondering how this panned out for you? I understand your neighbour's concerns that any moisture that would normally have made its way through your house would end up in hers. I hope a positive result?

The Society for the Protection of Ancient Buildings have an advice line, they would be able to help you work out a way of getting the most out of this space without damaging the fabric of your and your neighbours building. Alternatively there are specialist conservation surveyors that would advise.
Bare in mind that these were probably never designed to be habitable spaces.

Think it was on grand design type of program something similar
they tanked but there was a ventilated gap between tanking and original wall it also had drainage as well

the problem is if you seal your side the moisture can only travel through her side

Interesting. It's just that the linked neighbour of somebody I know is also tanking the basement of a previously 'breathable' building. Party wall surveyors will specify what to do so it would have been interesting to know what happened in this case. Luckily I live in a detached house(only just detached!) but was thinking of moving. Last thing you want is dealing with issues that may cause structural changes but I guess that also depends on what kind of ground the house is on.