damp (dare I say "waterproof tanking".....)

[Dan_F]

Ok. We have recently moved into an old stone house with a big damp and high humidity problem.
I know that tanking is a big no no when it comes to traditional stone rubble walls, and I've just spent a couple of weeks removing cement render and gypsum plaster to try and allow my walls to start drying out/breathing.

But... we have one ground floor room with the back wall buried into a hillside. It's a thick limestone wall and at some point in the 70's/80's someone tanked the wall (rather badly).
What are my options here? On the outside the wall is buried with moisture from the hill running past and therefore I'm assuming that the wall is never going to 'breathe'. In this instance, is there a logic to applying a modern tanking system to the part of the wall that's underground?

Don't want to make a bad decision and I'm very appreciate of any wisdom!

Cheers
Dan

 

[a twig]

Would you be willing to consider external works? Digging down the outside wall, installing a geotechnical membrane against the wall and putting in drainage would probably be the best bet if you wanted to maximise internal space.

Otherwise the current approach is to fit a drainage system. This effectively involves having a false inner wall with a waterproof membrane so that moisture can drain down behind it, be directed into a sump and then be carried away using an electric pump.

These newer systems are more cost effective than applying tanking. They are generally unobtrusive, as the pump only runs when the water in the sump reaches a certain level. They will require ongoing maintenance to the drainage pump, so this needs to be placed in an accessible location.​

 

[davidward89]

Would you be willing to consider external works? Digging down the outside wall, installing a geotechnical membrane against the wall and putting in drainage would probably be the best bet if you wanted to maximise internal space.

Otherwise the current approach is to fit a drainage system. This effectively involves having a false inner wall with a waterproof membrane so that moisture can drain down behind it, be directed into a sump and then be carried away using an electric pump.

These newer systems are more cost effective than applying tanking. They are generally unobtrusive, as the pump only runs when the water in the sump reaches a certain level. They will require ongoing maintenance to the drainage pump, so this needs to be placed in an accessible location.​

Hi, I've a similar issue in my property. Would you mind explaining what a geotechnical membrane is please? Thank you

 

[erikwoolf]

Ok. We have recently moved into an old stone house with a big damp and high humidity problem.
I know that tanking is a big no no when it comes to traditional stone rubble walls, and I've just spent a couple of weeks removing cement render and gypsum plaster to try and allow my walls to start drying out/breathing.

But... we have one ground floor room with the back wall buried into a hillside. It's a thick limestone wall and at some point in the 70's/80's someone tanked the wall (rather badly).
What are my options here? On the outside the wall is buried with moisture from the hill running past and therefore I'm assuming that the wall is never going to 'breathe'. In this instance, is there a logic to applying a modern tanking system to the part of the wall that's underground?

Don't want to make a bad decision and I'm very appreciate of any wisdom!

Cheers
Dan

We had a similar problem, external bathroom wall basically underground as the property is build on a slope. We got few damp proof specialists coming to advise. They all said internal tanking as most cost effective and easy solution.
We found a good builder and went for external tanking. We broke down the work to keep the price down.
We hired an experienced groundworks contractor to excavate down to the foundations (2 meters deep) across the whole wall. Then our builder applied external tanking. We used the permagard system with MB2K slurry, including the geodrain membrane and drainage system at the bottom. We still need to manage the moisture internally which means DMEV with Humidistat in that room along with keeping the temperature constant. Internally we applied Diathonite to that wall.

For the moment it works well but it is early days. Need to see what happens over the winter and reach the 1 year mark to see if it really worth the money and effort. It was the most stressful part of our renovation.
In terms of internal vs external tanking system preference, I think current knowledge suggests that you should try and combine systems for better results but from the reading I did there is definitely a preference to go for external tanking if there is an option to do that.

 

[Zebra]

Could it be another candidate for the Zebcolm trench? https://www.periodproperty.co.uk/forum/threads/the-zebcolm-trench.17575/post-235758

 

[a twig]

Hi, I've a similar issue in my property. Would you mind explaining what a geotechnical membrane is please? Thank you

One of these in this particular application:

PermaSEAL 8 Geodrain Membrane 20m²

An 8mm stud external waterproofing membrane with Geotex, a filter fabric, thermally welded to the studded face. It is used externally below ground in conjunction with a land or French drain to protect new build basements.

www.permagard.co.uk

 

[DeeGoo]

Hi, I'm interested to know if the OP decided on a course of action. I have a stone house where one wall is also c. 1m below the ground level on one wall. This is due to alterations by a previous owner in the 90s. Struggling to know who to approach and trust for best advice as there is so much complex and conflicting info!

 

[a twig]

I had a similar problem, initially this was going to be my approach:

Now there are utilities and this lovely concrete ramped path. The path is entirely my neighbours, I have access along it but it ain't mine. From presence of gravel etc on neighbour's side, there is some sort of drainage set up going on for him, and he doesn't have a problem.

Now - floor level of my dining room is approx 1 - 1.5m below my nice blue circle as the water supply enters in the bottom corner of my dining room. Neighbour is adamant on maintaining concrete ramped path, so whatever solution I implement would have to essentially end up back at the status quo - but is happy for me to dig up part of the path as long as he keeps his access to his front door during the works and I "put it all back afterwards".

I have lime plaster inside and lime pointing / mortar outside as this was the "easiest" fix - hoping that moisture could leave faster than it arrived, and it does work, the wall does dry out, but dining room wall does stain as inevitably some dirt etc is carried in by the water coming in from outside - in particular around where the water pipe enters the property as it seems to track along it, but also one or two other smaller areas.

Given utilities etc - I'm thinking excavate by hand, geotex membrane up against the wall, install proper perforated pipe french drain as far down as I dare to go before I start messing with the non-existant foundations, backfill with 20m gravel then slap a token 2" concrete on top to satisfy neighbour. Then either "let" the membrane into the wall above ground ( similar to how one does with flashing) or "render" it in with NHL up to 6" or so above the path height.

Thinking is as follows:
1) Stop damp from ground coming in by giving it an easier path away (geotex, drain, gravel)
2) Lime plaster inside should let any other moisture from any other sources (condensation, steam from tandoori chicken etc) back out again through usual breathability stuff - and shouldn't cause stains.

It actually turned out I didn’t need to adopt that approach, the staining was from the wall drying out after being repointed externally, and after a few months the staining stopped and all was good.

Ventilation was helped by the massive extractor hood in the adjacent kitchen

 

[DeeGoo]

I had a similar problem, initially this was going to be my approach:



It actually turned out I didn’t need to adopt that approach, the staining was from the wall drying out after being repointed externally, and after a few months the staining stopped and all was good.

Ventilation was helped by the massive extractor hood in the adjacent kitchen

Thanks very much for your response and Im glad you got it started. It's a minefield!

 

[MBozz]

Hi all. We have a similar issue with a house that is buried perhaps 3 metres into a slope at the rear, and following rains has a lot of water coming in, while it suffers from damp all year around. I was wondering how you all got on? The Geotec membrane complete with drain sounds like a great option if we are able to get enough earth away to install it. Would love to hear if this approach has worked for you, and if you have any more recommendations?
Cheers, Matt

 

[Toby Newell]

Would you be willing to consider external works? Digging down the outside wall, installing a geotechnical membrane against the wall and putting in drainage would probably be the best bet if you wanted to maximise internal space.

Otherwise the current approach is to fit a drainage system. This effectively involves having a false inner wall with a waterproof membrane so that moisture can drain down behind it, be directed into a sump and then be carried away using an electric pump.

These newer systems are more cost effective than applying tanking. They are generally unobtrusive, as the pump only runs when the water in the sump reaches a certain level. They will require ongoing maintenance to the drainage pump, so this needs to be placed in an accessible location.​

that ^^ you don't even need the membrane in all cases, its more important to dig the drain inside and instal a lift pump. The hydrostatic pressure is greatest at the bottom of the wall anyway. Tanking, obviously, is best done to the exterior!

 

[Dan_F]

Apologies for the delayed update.
I've been around the houses and head scratched a lot!

Following my most recent conversation with a surveyor at Heritage House, we have decided to not tank the below ground limestone wall. They were adamant that tanking it would not help the building!

Instead i've stripped off the internal gypsum plaster and the historic internal newton lathe waterproofing that was behind it.

I'm surprised that the stone wall doesn't look that bad. not too wet.
So i'm going to simply lime plaster the wall.

In conjunction with other measures....
(replacing the concrete ground floor with an insulating limecrete floor and installing PIV to improve ventilation)
.... i'm hoping this will be enough!

time will tell.