Cobbles in Basement (damp smell)

[Matty0682]

I live in a 200 year old property with a basement. The basement floor is s combination of flagstone and cobblestone which have been sealed (not sure what with but is transparent, see first pic).

There was a smell of damp coming from beneath the basement stairs (the area was sealed off). I have exposed the area under the basement stairs. and there are more cobblestone but not sealed with anything.

What can I use to seal these cobblestone? At the moment I am using a dehumidifier and letting it breathe.

Or do I leave it as is? (I have removed as much soil as I can and washed them)

Thanks

 

[Kearn]

Leave them be. And get as much airflow as possible - if the rest is sealed, that’s the only area of your basement that’s able to evaporate moisture.

Sealing is the incorrect approach. Basements were never intended to be habitable spaces, they were intentionally cold.

I’d be inclined to remove the mortar lines on the flags and repoint in lime and remove the muck that’s filled in around the cobbles. This will help a bit with incremental moisture management.

 

[Cubist]

Fully and firmly concur with Kearn but would add that what you've been doing is rather pointless and will do nothing to help improve the situation - you've already done that simply by exposing this area to the rest of the basement.

Also, that is a perfectly natural outcrop of rock rubble exposed by the builders when the basement was dug out. Cleaning out the centuries/millenia of silt and soil washed into the crevices between those rocks can only weaken the conglomeration and cause elements to come out. You're doing the wrong thing, please stop and brush the waste back into place.

 

[Stevers]

Under the stairs reminds me of a natural stone wall laid on it's side, so I think 'cobbles' would describe it best, and yes 'sealing' it is not an option - ventilation is the way to go.

 

[Matty0682]

Thanks all. I will remove the mortar lines on the slabs in the rest of the basement.

I may even lift all the slabs in the future to let the whole basement breathe (prob in the summer).

 

[Kearn]

No point lifting slabs. You’ll just have a mud floor! And possibly damaged slabs. Remove the surrounding modern crap as above, that will help them release moisture. Then get ventilation. Cross flow essential. Forced possibly. A humidifier you will simply be emptying daily!