Cellar damp proofing in mid-terrace

theoretica

It's a mid terrace - my cunning plan in such situations is to let all the neighbours know you are puzzled over your cellar and see who wants to show off about what they have done/how good theirs is.

Apodemus

If you put a dehumidifier down there, you would need to keep the windows shut and you will just be sucking more and more water out of the ground (and your neighbours cellars), which is likely to be an expensive, losing battle.  Providing heat and keeping the windows open, might be better, but very expensive.  Cheapest option would be to spray the bikes with WD40 every time you put them away.

Jeepers_Creepers

Jd843 said:

We kept the window open for a while to try and keep it ventilated, but obviously this makes it colder too, which won't help with the damp (?).  What would be the best course of action, if any, to be able to store things down there? Is a dehumidifier a good idea?  Keep the window open or close it?  And what about heating it?

It seems counter-intuitive at first glance - the cold/damp connection. There is often a connection, but really only where the moisture is being generated in a warmer area, and then condenses out on cooler surfaces. That is not the case here.

With the situation in your cellar, the moisture is coming through the floor and walls. You aren't going to stop that without extensive works. So, your cellar has 'damp'. How to sort/remove/control this? By blowing it away - ventilation. Ideally a through-flow from one end to the other. Can you arrange this? If so, try it.  Give it a day, and try the hygrometer again.

Won't this make the cellar feel colder? Yes, but so what! It'll be drier, and that's what counts.

Would shutting off the ventilation and putting a heater in there work instead? Think about what this would actually do... Would it stop the damp coming through the walls? No, of course not. Would it make the air in there drier? No - wetter! How? Because warm air holds more moisture than cold air - I think you'll find the hygrometer will go off the scale...  It'll be warm and clammy - like a sauna. Will your bikes remain rust-free? Only if you heat them too, to a point where this huge humidity cannot condense out on them.

But the coolest surfaces in this warmed and unventilated cellar will be running with condensation.

Will adding a dehumidifier help? Yes, to some degree - it's hard to work out how much (depends on how big it is, I guess). Does this make sense? Only if you can tap into next-door's mains supply, because you'll have to keep it running constantly for any benefit. As soon as you turn it off, the humidity level will soar again.

Is your garage damp? No? Not even on wet days? No - because it's also draughty. Is it chilly in there? Yes. Is that a prob? Nope.

If your garage floor gets wet (left the door open during rain, burst pipe etc), how do you dry it? Stick a heater in there? Install a dehumidifier? Open the garage doors/windows for an hour and just leave it?  One of these will work faster than the other two, and cost nothing.

Whether your cellar can simply be tanked, I cannot comment on this. As said by others, you need to be really careful that this doesn't add different - and more serious - problems to your house. For instance, at the moment your floors and walls have damp coming through them, but this presumably evaporates before it gets too high up the wall - eg to your house's floor joists or soft bricks. What would happen if you tanked the visible walls and floor down there? Almost certainly it would give you a drier cellar, but would the trapped moisture in the walls now travel further up to escape? (The answer is - I don't know.)

Meanwhile, prove to yourself the difference good ventilation will make. How many windows and vents do you have down there? If only one, the effects will be limited (tho' should still help). Is there any way to add vents on the opposite wall? Could you bore holes through to the outside?

FreeBear

I might be tempted to put a small extractor fan in on the wall opposite to the airbrick (and shut the vent in the door). That would ensure that there is a good through draught and wouldn't cost a huge amount to run, unlike a dehumidifier.