How do you damp proof a cellar wall externally?! Damp can be a major issue in the home. Find answers to questions or post your own here.

[nonothingbozo]

Hi All, I have a nightmare house which keeps throwing up random problems... the latest is this: damp in the kitchen walls (suspended floor in rear extension) and the cellar (under the main house). Now, we've had a couple of people round who seem to know as much as me and go for the usual solutions of 'stick in a dpc, redo your plaster and we'll charge you'. however, the last guy pointed out that there is a brick arch at ground level which was probably where a set of old steps led into the cellar from the side return. now this has been filled in and we are guessing not waterproofed properly... so we will excavate back down and re-waterproof it but:
[b]How do we waterproof a cellar wall externally?[/b]

Thanks,

Jon

[mdpmspitfire]

hi jon , not easy to waterproof cellar walls externally as lots of excavation required. internally however, you could apply two coats of cement based tanking, render the walls with a waterproofer and salt inhibitor and then skim with multi-finish plaster. this is usually a profesionals job so depends if you could take it on. providing there is no future wall movement, the fix should last you 30 yrs.
mark

[nonothingbozo]

Thanks Mark,

The funny thing is that one of the quotations includes us breaking out the external concrete slab next to the wall (in the side return) and then they will install a new slab... for £1000. And I have no idea why they are doing it or what it will achieve? Are they just going to put some DPM under the concrete? In which case, there will still be damp soil up against the cellar wall - whereas I assumed they would want to excavate down and install a vertical DPM or injected DPC. (it's not very wide so could be possible to excavate).

Basically, I don't understand what they are proposing or really what we need to protect from - damp earth or water coming through the slab?

Thanks

Jon

[mdpmspitfire]

hello again. i cant understand the relevence of breaking out and replacing a concrete slab. maybe the contractor thinks water is getting through it. but the ground will be damp throughout anyway.you are trying to achieve a barrier between the external wall and inside surface. either you can completly seal the external surface to the full depth of the cellar and allow the wall to dry out which could take a year or you can leave the wall fabric wet and apply and internal sealer coat and stop damp from penetrating through. dont forget also that the floor if damp may need to be included. as far as tanking is concerned, i have carried out this process many times as provided you do not drill through or puncure (use adhesives for everthing to be fixed back) it works very well.
regards
mark

[the specialist]

Hi, you cant make a tank with only one wall! The most succesful way to create a dry cellar/basement is to install a cavity drainage membrane system to all walls and the floor. It is usually carried out by specialists but could be done by a competent DIY person.

If you try and waterproof the external wall I guarantee it will fail because moisture will simply come round the edges. Also you have no way of stopping moisture from penetrating at the wall to floor joint - which is the area subjected to the greatest hydrostatic pressure.

I recommend you do this job properly or you will throw a lot of money away and you will still have a problem.

A

[TheDoctor5]

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