How do I control damp in my cellar?

Claxton_Blaine

Hi
I have read through many previous threads on this forum but cannot find anything that matches my situation.

Basically I live in a 3 storey Victorian end terrace. It has a 3 room cellar (below ground level) accessed by a door under the stairs. One of the rooms is not accessible and only has air bricks going into it.

All the cellar rooms are ventilated through air grills from outside - in fact a huge amount of air goes through. The cellar ceiling was covered in the original lath and plaster which had various holes in where radiators had been plumbed in and new electrical wiring ran through. As the draught was coming straight up through the floorboards/carpet/laminate and into our lounge and hallway we have now pulled all the lath and plaster down (the dirtiest job I've ever done!) and filled in between the joists with rockwool insulation. The insulation is held in place with batons a few feet apart. We have left a gap between the top of the insulation and the floorboards. As we are not intending to use the cellar for living space we have not covered this over with plasterboard or similar so the bottom edge of the joists are still being ventilated. This seems to have made an instant difference.

However the cellar is, and always has been relatively damp - its not damp as in running down the walls but a cardboard box left on the floor will start to rot after 2 weeks. We only want to use this space as storage but would like to make it a little dryer if possible.

Does anyone have any idea what we could do while still maintaining the integrity of the structure. I know it's not a big issue compared to the damp problems some people have but there seems to be some farily knowledgeable people on here.

Thanks
Claire

Plasterer

Have a look at David Aldreds responses under (Damp, damp and more damp - girl in dire need of help please). He really seems to know his stuff.
Hope this helps
Regards P:beer:

David_Aldred

Hi Claire,
When you insulated the floor above the cellar you will have made the cellar itself colder and possibly more prone to dampness. You say there is a good draught throughout the cellar but the relative humidity remains high enough for the items you wish to store within this area degrade through dampness.

There are a number of options open to you depending how much you want to spend but laterally thinking before you dive into converting the cellar as a whole you might want to consider fabrication of a dry store container that is an appropriate controlled environment seperate from but within the main cellar itself suitable for the items you wish to store within it if on a small scale.

If the number of items you require a greater level of dryness for are considerable such that most of the cellar will be contained by them then you will have to consider how to achieve this to the cellar itself. Without structural waterproofing the floors / walls you may wish to opt for simply mechanically removing a greater amount of moisture laden air than the current background ventilation.

However please be aware that at present the cellar is in equilibrium - that is to say the amount of moisture permeating into it and occurring within it is in balance with the rate of natural ventilation. If you start to dramatically increase this extraction process by fan or dehumidifiers then there is a risk that the rate of moisture entering the basement may go up to match the rate of mechanical extraction. I am not saying it will but there is a risk.

Cellars are variable to say the least and whilst you may get away with doing something on the cheap such as dry lining or coating wall surfaces in one basement if it is inherently constantly relatively dry to begin with you can just as easily be wasting a lot of time and money doing so in another making the area smelly damp and a heaven for dry and wet rots.

Even if you choose to ignore their advice I would recommend you have somebody come and physically have a look who knows what they are on about with regard to basements and as such somebody who is not a contractor but who is a Certified Surveyor in Structural Waterproofing (CSSW) qualified. Such surveyors can be found upon the Property Care Association website under the heading of Freelance Surveyor (the rest are contractors) for one in your area to have a chat with.

Hope this helps,

Kindest regards, David Aldred Independent damp and timber surveyor

DVardysShadow

Cellars and damp are a mystery to me. Our cellar felt very damp and smelt very cellar like - and a nasty whiff with an element of ammonia. But then we took up the carpet and underlay left by the previous owners. We expected to have a damp floor, but the concrete slabs underneath are as dry as a bone. It still smells of cellar, but in a much nicer way.

Claxton_Blaine

Thanks very much for your help everyone (as always on here!). David I'll take your advice and get someone in to take a look.

DVardysShadow - too right - they are definitely a mystery. Feel better now we've been through it and not found any bodies!

Thanks again.:j

PatsyMcM

Hi Claire,

You must CLOSE ALL VENTS to your basement. Stuff them with insulation and cover them permanently.

Fresh air is great upstairs but not in the basement. Because the basement is protected from sunlight heating and from the warmth of outside air during the warmer months, it will always be cooler and will attract humidity from the outside air as it shrinks in the cooler basement. Keep all doors and windows to the basement closed year round also.

Run a dehumidifier in your basement hooked to a drain hose so you don't have to empty the water out. Once the excess humidity is removed from the air, your dehumidifier won't run so much until the humidity is replenished from outside air entering the basement. There is no problem going in or out of the basement, just close the door behind you to limit how often your dehumidifier runs.