DIY Doctor UK DIY Forums

Hello all

I’m hoping to get some advice from some of you on how to insulate and reduce moisture levels in my cellar. Hopefully making the room more usable as a universal space for living/office/guest room type area.

The gist: Our house is 260 years old and has a cellar approx 6.5 meters x 7 meters with a concrete floor laid on a DPM that has approximately 6-8 inches untrimmed coming up the walls.

The cellar has no damp or flooding problems, there is a deep 3-4 foot deep pit with a plumbed in sump pump to take away water. The cellar has been used by previous occupiers as a computer home business and a home mini cinema, so I know it has not flooded in the last 25 years. We have also lived here through the wettest summer and wettest winter on record and it did not let in a drop. Although there are a few areas on the walls that feel damp to the touch and a bit of damp where the wall meets the floor, it has none of the usual problems associated with basements/cellars of this age.

I want to cut down the humidity and insulate 2 of the walls. Currently it takes a lot of energy to heat the room and 20 minutes after the heat is turned off the room is cold again.

I have chosen not to go down the cement-based tanking route for various reasons. The two options I am considering about are as follows:

1. Would it be enough to batten out the walls fitting celotex or some such material between batons and plasterboard over? Would this make what little damp there is worse?

2. The second option is to line these 2 walls with a dimpled cavity membrane tucking and taping the bottom of the membrane behind the 6-8 inches of floor DPM overhang. Then fix a stud wall in front, fixed to the floor and ceiling, again fitting insulation between studs then plasterboard over. Is this “over killâ€

It is possible that the ground round your house is sandy and of good drainage?
It is also possible that your fan contributes to the overall feeling of cold and damp merely by pulling in unheated damp air from outside.
As you say, we have been/are in a very damp patch at the moment, and for example my outside humidistat has shown 99% humidity for 24 hours a day for a number of days recently and has been 99% at some point every day for quite a while.
The previous owner seemingly used it successfully for his purposes?
I would recommend wait and see what happens through a year.
In the meantime, get and use a decent de-humidifier keep it on 24 hours a day and see how much water you collect.
Consider your use of the cellar, how many people use it, for how long, for what type of activity. Consider how much water vapour those people put into the room. Compare that with the amount of water you collect over 24 hours.
Taking the water vapour out of the room will help dry the walls and make it feel warmer.
Consider your heating strategy, raising and lowering temperatures, results in increased humidity and condensation onto and into the fabric of the cellar and its contents.
Keep the temperature steady - this will prevent condensation, only provide the amount of ventilation that the people and their activity require.

Hello Perry

Thank you for your reply. Yes the substrate here is a sort of chalky, muddy, ballast. So I guess quite well drained.
I will tank on board your comments.
Thank you again for taking the time to reply to me.