DIY Doctor UK DIY Forums

Hello

My GF and I bought our first house in April 2007. The house has a basement conversion (two approx 14'x14' rooms, one approx 10'x6' room), which (we were told at the time of purchase) is tanked.

We recently noticed some 'chalky' patches appearing on the walls - we attributed this to cheap paint! However, a couple of days ago I opened a cupboard in one corner of the basement and found what looks like damp behind some blankets - the skirting board has turned black and moldy and the wall is dappled and yellow.

I don't know how long ago the cellar was tanked or who did the work. I don't know what method was used to either - all I know is that the guy who we bought the house from told us we wouldn't be able to use long nails to hang pictures on the walls - I assume because this would damage the tanking.

In any case, we are now stuck with the damp and understandably want to fix it ASAP (before any more damage is done) and without breaking the bank. From my explanation is anyone able to infer what level of tanking might have been installed, what we might need to do to fix the issues and how much it might cost?

Worst case: the whole cellar needs to be fixed - what are my options and how much is this going to cost?

Thanks
Jay

Hi,

I lived in a basement flat which went from being damp due to external moisture through a sub surface level wall to being damp due to internal moisture caused by condensation following tanking. All the symptoms were the same, similarly I was warned against piercing walls and you are correct that this was to prevent damaging the membrane. The flat was made more livable by cladding the external walls with ploystyrene insulated plaster board which looked great when finished, this also stopped the white salts being deposited on walls which ruined wall papering and paintwork (this i believe is caused by an electrolytic reaction through the wall fabric).

At this time they also fitted the humidity triggered fans to automate the ventilation although I think these are a bit of a white elephant or were at the time.

From what you have described I am sure the problems you are experiencing are due to condensation from natural perspiration and breathing having no way of escaping other than condensing on a cold wall and can be kept under control by a dehumidifier or perhaps more permanently by insulating walls and improving ventilation, whether this is by always keeping a window cracked open at each end of a property or by installing fancy fans and air bricks is down to your budget.

I would suggest buying a dehumidifier and running this for a day and see if you notice the difference, if carpet feels crunchy under bare foot then it is working and this is how mine felt after running the dehum.

Good luck and personally, following my experiences (which were at no cost to me and paid for by a landlord) I'd never consider buying a property with historical damp problems regardless of whether tanked or coursed, I think it just moves the problem around and you always seem to have to settle for less than you would like, it's like nursing an injury you can't fix!

Having re read your post the black mould is the clincher, this is caused by condesation and not external moisture - or so said the independant damp expert who double checked my landlords builders work

Hello Rinkerdink

Thanks so much for replying. This is the same conclusion we have come to, after talking to a few local (builder) friends. Clearly the guys who came round to quote us for fixing it (and gave a price of £15-20k) were just after making a quick buck.

Thanks again, you've set me mind at rest and I'll try the solutions you advise - I've already set up some fans down there to keep the air circulating and I am opening the external windows whenever possible.

Cheers
Jay