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Hi all. Have a nasty problem with damp in our basement. Getting worse and quite a nasty smell. Some rising damp at ground floor level too but early stages and only in spots. Had a quote but not sure about it. Can anyone recommend someone to help me get this sorted before the Winter?
Brendan
I am certainly no expert, & not knowing your personal water situation ( water ingress, condensation etc... ). It's not normal to have damp proofing in many houses. Start first with ventilation, so any moisture may escape. See if that helps the problem. V
Posted: Wed Sep 2, 2026 1:18pm
Super helpful member
Agree with previous post put in a few ventilation holes so air can circulate, it will help, at least it will do away with the smell of Dampness, 4 inch/ 100mm is adequate
Villas wrote on Wed Sep 2, 2026 12:45pm:
I am certainly no expert, & not knowing your personal water situation ( water ingress, condensation etc... ). It's not normal to have damp proofing in many houses. Start first with ventilation, so any moisture may escape. See if that helps the problem. V
Thank you. I think more serious than that. Apparently there is an underground river nearby that is probably the main cause. Ground floor is less of a problem but the basement is pretty bad
Sligogent wrote on Wed Sep 2, 2026 1:18pm:
Agree with previous post put in a few ventilation holes so air can circulate, it will help, at least it will do away with the smell of Dampness, 4 inch/ 100mm is adequate
Thank you. Ideally looking for a contractor to deal with it but no idea what it entails.
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BY 2026 wrote on Wed Sep 2, 2026 1:27pm:
Thank you. Ideally looking for a contractor to deal with it but no idea what it entails.
I had a similar situation ( & others) in the campo years ago. Diverting the water ingress ( away from your property). Use a local who knows the situation, may help. If your property is on an incline, it makes it simpler. (eg: Channel away). V
Posted: Wed Sep 2, 2026 1:51pm
Helpful member
Probably a waste of money but you can try a French drain on the exterior.
As this is an earthquake region, impossible to do anything with the point between the foundation and wall except bring it down to block and spray a waterproofing liquid on it, then render it with a waterproof render. You can also remove the floor, place a plastic or fabric barrier (this can go up the wall also) then re screed 7-10cm and add your tiles with swimming pool grout.
As said, ventilation is important.
Posted: Wed Sep 2, 2026 6:29pm
Very helpful member
Assuming your basement is only used for storage as designed, I would suggest a dehumidifier which is adequate for the size of the room and once that has dried out, then look at the floor above. IMO it is no good doing anything with upstairs before the basement is sorted. Once it is, it is possible that by cleaning where the mould is with a suitable cleaner and using anti-mould paint, the problem will go away as long as there is a lot of ventilation.
If it doesn't, I think you will have to bring the professionals in at a much higher cost.
If you are not a resident and will be leaving the property for some months, you will need someone to empty the dehumidifier regularly, from every 6-12 hours to every 2 or 3 days.
Basements/underbuilds are a constant pain from what I have read.
Are you on low ground or hillside and is your property shaded by Montgo for much of the winter?
If you think it is caused by a nearby underground river you can do as Ray Benidorm suggests.
What did the quote include?
Flyingduck81 wrote on Wed Sep 2, 2026 6:29pm:
Assuming your basement is only used for storage as designed, I would suggest a dehumidifier which is adequate for the size of the room and once that has dried out, then look at the floor above. IMO it is no good doing anything with upstairs before the basement is sorted. Once it is, it is possibl...
Read more...
...e that by cleaning where the mould is with a suitable cleaner and using anti-mould paint, the problem will go away as long as there is a lot of ventilation.
If it doesn't, I think you will have to bring the professionals in at a much higher cost.
If you are not a resident and will be leaving the property for some months, you will need someone to empty the dehumidifier regularly, from every 6-12 hours to every 2 or 3 days.
Basements/underbuilds are a constant pain from what I have read.
Are you on low ground or hillside and is your property shaded by Montgo for much of the winter?
If you think it is caused by a nearby underground river you can do as Ray Benidorm suggests.
What did the quote include?
Thank you for the reply. Am a resident so doing nothing isn't an option. Dehumidifier would only be a temp solution I think. I would prefer a more permanent solution. Speaking to some builders at the moment and trying to get a handle on what is best. Going to take in as much info as I can, take my time and try to find the best option. B
Posted: Wed Sep 2, 2026 7:10pm
Very helpful member
BY 2026 wrote on Wed Sep 2, 2026 6:37pm:
Thank you for the reply. Am a resident so doing nothing isn't an option. Dehumidifier would only be a temp solution I think. I would prefer a more permanent solution. Speaking to some builders at the moment and trying to get a handle on what is best. Going to take in as much info as I can, take m...
Read more...
...y time and try to find the best option. B
Good move. Please let us know what options the builders are giving as I know this type of problem has cropped up before and someone may be able to say what did or didn't work.
Best of luck
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