Discussion Forum
Tanking Coal Holes

From Joseph S
Wednesday, 5 September 2007

Does anyone have any experience of lining your coal hole to make it dry enough to store bikes & stuff in? If so any tips or do you know anyone who can do it? It must be a commonish thing around here as loads of us have store rooms built into the hillside.

Posted by Graham Barker
Thursday, 6 September 2007

Posted with some hesitancy, as I only have limited DIY experience of this. Main thing is to let the wall 'breathe', because it's unlikely you'll ever completely stop damp seeping through - and cellar damp is often worse in summer, not winter.

Therefore, I wouldn't use one of those paint-on damp-proof treatments. They form a skin that traps moisture in the wall, where it will build up and eventually push through the skin, rendering it useless. (This happened to a friend's cellar, within two years.)

I'd try dry-lining with timber studding and plasterboard with plastic sheeting behind it, but leave an air gap of at least an inch between wall and both timber and liner. If possible, I'd also try to increase ventilation to the air gap and put some kind of drainage in to take care of any potential build-up of water.

Hope this helps. It may at least coax a professional to come out of the woodwork and say, 'No, that's not the way you do it...'

From Joseph S
Friday, 7 September 2007

Thanks Graham, thats really helpful.

From Giles M
Sunday, 9 September 2007

Tanking is always an expensive option but the only serious one to hand. If headroom permits go for a complete lining of your entire coal hole – inc. floor.

There are quite afew Dutch systems on the market (…the Dutch are experts in reclaiming wet land!). You could also check whether all walls/floor are damp yourself by hiring a damp meter from HSS for about £15. As Graham posted it involves timber battens, plastic sheeting and plasterboard.

A little more detail… you have to hack off any damp plaster to begin with & dispose. Doing this yourself is messy but will cut labouring costs if you intend to get someone in to do the lining work. Timber battens are then fixed to the walls to take the plastic ‘egg crate’ sheets (fixed using neoprene sealed damp proof fixings and sheets are taped together) and then the plasterboard finish.

The battens also provide the ventilation gap behind. You may also want to put in some moisture resistant plywood to sheath behind maybe one wall so that shelves etc could be put up/bikes can rest against as drylining p/board is not v. durable as will get damaged by bikes etc v. quickly if not fully supported behind.

Also, any electrics will need to be brought forward into the ventilation gap and sockets obviously need to be flush with plasterboard and fixed to battens using neoprene fixings also…. as you do not want any penetration through the plastic sheeting at all.

Drylining is pretty expensive but works for a much longer period than paint applied DPM’s (Damp proof membranes)… but if it is only your bikes… maybe stripping & reapplying a liquid DMP every few years is a more appropriate option. Or if you can afford to lose, say 130mm per wall from the width of your coal hole, a cheaper option would be to lay a new screed over a polythene type DPM on floor & line walls with an 80mm ‘breeze’ block & cavity. This is a much more bike friendly option. Maybe different walls could have different solutions to meet your budget and function needs. Graham is right… venting the space would help a lot.

If you do get someone else to do if for you… make sure you get the guarantee before you pay up!!!!

From Joseph S
Monday, 10 September 2007

Thanks Giles for taking the time. Very useful :)