Tanking a basement

[kurt535]

Has anyone here successfully tanked their basement? We are talking a Georgian vaulted space, one of several underneath a former hospital which has been sliced and diced into various flats, etc.

The ground floor flat I'm looking at comes with the basement which has been bricked up from the one next to it so it's self - contained. Dealing and solving damp issues in listed buildings above ground is something I have a lot of experience in but below ground is very new to me and something I have always avoided taking on.

Ive been doing lots of research online into available methods but reading anyone's experiences on here would be very valuable.

Ty

[037]

http://www.pamties.co.uk/
Call and ask for Paul Hughes. He knows all there is to know about basement conversions

[Eddieslofart]

If you cannot tank from the outer skin, you’ll need a sump pump for inner skin tanking.

[B17NNS]

Walls are relatively straight forward. Just use an air gap membrane and then board and skim.

As above you'll need to consider a sump pump for the floor.

[kurt535]

Three walls - I think - are outer skin and one wall is internal to the next vault.

I went to the link as well, lots of new toys there; any idea whats the level of complexity in me and my boys doing it as opposed to subbing it out? open ended question for sure but some jobs i know when i am beaten so don't start them

[227bhp]

Eddieslofart said:

If you cannot tank from the outer skin, you’ll need a sump pump for inner skin tanking.

Not if there is no running water.

[C Lee Farquar]

Have a look here They helped spec and oversaw the first two I did, but that was 20 years ago and in Bristol. They were three blokes in a Nissen hut then.

As recommended by most, cavity drain system would be the way to go. There's no reason you couldn't do it yourself, if you cock it up you can do patch repairs. That's one of the plus points of the system.

I wouldn't consider cementitious tanking with vaults.

As to whether to have a sump. Ask yourself if the cellar could possibly flood in the lifetime of the tanking. Your call, I always installed one in basements where there was a high external ground level. If the ground falls away sometimes you can drain outside rather than having a pump.

[TA14]

227bhp said:

Eddieslofart said:

If you cannot tank from the outer skin, you’ll need a sump pump for inner skin tanking.

Not if there is no running water.

Where does the water go without a pump?

[TA14]

C Lee Farquar said:

Have a look here They helped spec and oversaw the first two I did, but that was 20 years ago and in Bristol. They were three blokes in a Nissen hut then.

As recommended by most, cavity drain system would be the way to go. There's no reason you couldn't do it yourself, if you cock it up you can do patch repairs. That's one of the plus points of the system.

I wouldn't consider cementitious tanking with vaults.

As to whether to have a sump. Ask yourself if the cellar could possibly flood in the lifetime of the tanking. Your call, I always installed one in basements where there was a high external ground level. If the ground falls away sometimes you can drain outside rather than having a pump.

these are also good for mats and design: https://www.barbourproductsearch.info/Grace%20Wate...
you should be able to tank the three external walls on the outside inc the party wall thickness OK then hope that that will be enough. That of course leaves the internal wall and the floor. A nominal system for the internal wall should be straightforward the fllor more complex and I wonder what will be allowed in a listed property.

[kurt535]

thank you for the responses.

all valid and most helpful.

using the pump method is preferred as it appears to remove hydrostatic pressure. fitting two pumps looks the best belt and braces approach too.

im going to speak t the conservation dept on monday and get an idea on their outlook.

one thing i am not entirely clear on is as the basement already exists, do you need permission to convert? on the basis its grade 2* i suspect id have to!

[anonymous-user]

We tanked the basement of our first house (Georgian terrace).

We had all the plasterwork stripped (whcich meant losing all the skirtiings, door frames and so on). Certain areas of the brick were soaking. The contractors injected a chemical DPC into the bricks at skirting level, and aroud the soaked brickwork area. Every was plastered with a silicon based plaster undercoat (Sika, IIRC) then a regular top coat of plaster. Can't remember what they did with the floors now (which were concreted).

It all worked fine. We couldn't pierce the plaster undercoat though unless we used these little glass ampules of epoxy resin in the hole before putting a bolt in the hole. Everything had to be glued to the walls.

That cost 10k for four rooms in the early 90s, central London pricing.

[MGTS]

We used the Wykamol system - highly recommended. It sorted out our damp problems completely

Video here on their website explains how it works http://www.basement-living.co.uk

And here is more details of the products

http://www.wykamol.com/waterproofing

[B17NNS]

Greg66 said:

We tanked the basement of our first house (Georgian terrace).

The contractors injected a chemical DPC into the bricks at skirting level

Eh? What use us a DPC underground?

[mcg_]

I've looked at doing our cellar before. Previously the thought was to have it as and additional room, with tele etc. Got knocked on the head though as we will never really use it and we're looking to move in a couple of years.

Been thinking about it again though recently, this time though with the intention of it's primary purpose being for storage. I still want it to look good though, a bit industrial. Thinking to just slurry, then paint the slurry. Engineered oak on the floor (got some left over) and painted white tongue and groove on the ceiling. Then exposed electricals. galvanised type fittings. Doing everything myself apart from the electrics.

Last time my plan was to tank it, then use metal stud, the moisture resistant backed plasterboard and then skimmed. Not sure if that would have worked, didn't get too far into the research.

Found this company which seemed pretty good. http://www.constructionchemicals.co.uk/Tanking-Slu...

Their how to https://www.youtube.com/watch?v=D7wRMDDnuqE

Would hire this scabbler to clean the wall down http://hire.travisperkins.co.uk/hire/productDetail...


That Perma Gard posted above looks good too. It does say you can't paint onto the slurry though, something I'll have to look into.

[C Lee Farquar]

mcg_ said:

I've looked at doing our cellar before. Previously the thought was to have it as and additional room, with tele etc. Got knocked on the head though as we will never really use it and we're looking to move in a couple of years.

Been thinking about it again though recently, this time though with the intention of it's primary purpose being for storage. I still want it to look good though, a bit industrial. Thinking to just slurry, then paint the slurry. Engineered oak on the floor (got some left over) and painted white tongue and groove on the ceiling. Then exposed electricals. galvanised type fittings. Doing everything myself apart from the electrics.

Last time my plan was to tank it, then use metal stud, the moisture resistant backed plasterboard and then skimmed. Not sure if that would have worked, didn't get too far into the research.

Found this company which seemed pretty good. http://www.constructionchemicals.co.uk/Tanking-Slu...

Their how to https://www.youtube.com/watch?v=D7wRMDDnuqE

Would hire this scabbler to clean the wall down http://hire.travisperkins.co.uk/hire/productDetail...


That Perma Gard posted above looks good too. It does say you can't paint onto the slurry though, something I'll have to look into.

The reason why they say a painted finish isn't recommended is condensation. Water runs off the walls, leaving you thinking the tanking has failed. Think bathroom window after a shower.

Ideally you want to render before and after the slurry. If you tank directly to the walls you run the risk of salts and other nasties in the mortar joints blowing your tanking barrier. If you cock it up it's a big job to strip off.

[kurt535]

Does make me wonder what tanking methods 3rd Reich used for their bunkers 5-10 stories below ground!

seriously though i am pretty sure I will run with a pump method to take hydrostatic pressure off walls facing external earth. I appreciate they are harder to sort out if they go wrong but I reckon such a system is easier to sell on to next buyer

[C Lee Farquar]

It really is the simplest tanking system to sort out if something goes wrong, but it is important that the initial spec is right.

It's hardly rocket science but you need to get your head around the floor drains and how the material is joined and fixed.

Good luck

[Gary C]

Eddieslofart said:

If you cannot tank from the outer skin, you’ll need a sump pump for inner skin tanking.

Surely, as its one section of a large vaulted basement, the water will just go into the neighbours areas so he won't need a sump pump ?

But certainly, water will always want to go somewhere

[Lotobear]

B17NNS - indeed, I spotted that too!

[anonymous-user]

B17NNS said:

Greg66 said:

We tanked the basement of our first house (Georgian terrace).

The contractors injected a chemical DPC into the bricks at skirting level

Eh? What use us a DPC underground?

I guess the same as it is above ground: to stop moisture rising into the brick work.

Once the brick work was all exposed, you could see that the main wet areas were the four corners of the house, where the structure touched the surrounding land (we had a void front and back; the side walls were shared with rooms rather than soil on the other side of them). The floor surface had had some work on it and you could see a DPM poking up at the edges here and there. I remember the contractors tested the brickwork with one of those little moisture sensors before deciding where to inject the chemical DPC and where to make the barrier out of waterproof plaster.

So I suppose bits of the side walls, all of the internal walls and bits of the front and rear walls were only susceptible to damp penetration from the ground, and either the water table wasn't high enough to push moisture up into the walls, or there was some much older barrier in the brickwork out of sight, or something else (dunno what).

Seems funny to think back to that time now. We'd just bought our first house, were completely skint, and yet had to spend what was to us a small fortune on having blokes use a pneumatic drill inside the house from 8am and then fill the house with plaster dust for three weeks. No CH and no HW for the duration of the work, then a long period of letting the plaster dry out slowly after it was done. Then a case of teach myself carpentry, tiling, electrics and getting that floor habitable in the evenings after work and at weekends. Inexperience meant I was incredibly nervous about cutting pieces of wood (I couldn't afford waste) so much so that some evenings were spent mostly measuring over and over again before making a couple of cuts and retiring to bed.