Capping off ventilation pipe to cellar

[jeremy rowe]

Hi, Apologies for dumping this query here but i don't really know where to post it as it seems to cover quite a few areas.

The question is really about how to cap off an old ventilation pipe into a cellar (which i believe is responsible for the cellar being more damp than necessary) which should have happened when i had my house renovated but the builders went bust......

By way of background the cellar had a ventilation pipe which was closed off in the cellar but not outside. This was so new ventilation could be put in with a humidity activated extractor fan (which is now all done). In the corner of the cellar where the old vent would have been the humidity level in the masonry is about 30% in the plaster and understandably the paint keeps coming off/ plaster starts flaking/ cellar smells damp. The cellar floor was dug out and a membrane installed. The walls were all given a double coat of thoroseal The rest of the walls have humidity levels at about 16%. The only problem appears to be in the corner where the old vent was.

Assuming the external opening for the vent is the problem, whats my best option for backfilling it so that its is as waterproof as possible in the hope that this solves the last remaining damp issue in my otherwise dry cellar? Concrete? Cement? waterproof render? some magical formula you guys know about that i have no notion of?

Any help gratefully received

Jeremy

 

[theprinceofdarkness]

Lots of info missing, is it a cavity wall with a plastic pipe straight through it? if so, cavity could be bridged. Is the outside air entry catching rain? or is it a buried air entry which is just filling up from ground water? Different arrangement require different solutions. Does the pipe actually go right through the wall and not just two stubs cemented in to make the hole look neat.
Frank

 

[jeremy rowe]

Hi Frank,
Thanks for your reply. Unfortunately id's not as simple as that. The house is mid Victoria cotswold stone. Internally I don't know what the builders did to close it off. It's plastered. Externally, there is a plastic pipe which comes up at floor level. There shouldn't be any rain getting in because that area is covered by an over hang, but I wonder whether condensation is forming inside the pipe and that's what is keeping that bit of wall damp. To be clear, the humidity level below the old vent is about 30% but the rest of the walls are about 16%. If I just back filled the open pipe with concrete that might work? I don't know for sure that that is the problem, but it seems like an odd coincidence if it isn't. I don't need the old vent opening for anything so I thought if I fill it it might improve. If it doesn't I might have to strip the plaster back and re thoroseal which I would obviously like to avoid if possible. Any thoughts?
Jeremy

 

[jeds]

I'm imagining a 4" external pipe coming out the ground which goes below ground and bends into your cellar some way below. If that's right I'd fill it with expanding foam, reduce it below ground level and cap it over with concrete, or whatever the surrounding ground material is.

 

[theprinceofdarkness]

When the builder installed this pipe he would have knocked a hole through the wall, I wonder if the damp from the soil is coming in around the pipe? One thing I would not do is to fill the pipe with concrete, it would make removing it very it very difficult. I would dig the pipe out, make good the hole with a waterproof concrete then back fill the hole to a level that is lower then the existing pipe hole, so any water finding its way down will drop to a level lower then your repair.
Frank