Hello Ive got a cellar with lime render on the walls. The cellar walls are largely surrounded by soil but in one area the exterior part of the house has had a buttress put on the corner and the interior of the cellar wall where this is a lot wetter and the render won’t solidify on the wall also the dampness has spread up from that area to other areas along the wall. Be grateful for any suggestions please. Tanking is not appropriate.
Hi, I have a Georgian cottage built in 1805 with a cellar. We keep ours dry with a combination of a good dehumidifier, good ventilation and ensuring correct materials are used on the walls e.g. lime wash, limecrete floors etc as appose to cement based plasters/renders etc. If I were you I would get a heritage surveyor to do a damp survey if it is causing significant issues. It is essential if you do this to ensure they are proper heritage surveyors as a lot of surveyors say they do listed/heritage buildings but lack a great deal of experience. I can recommend some that will travel to most parts of the country. You could even email them and ask for some free advice about the buttress.
Do you have pictures to help me get a better idea? There are so many things that could also be contributing to the damp even if it is on the part with the buttress. Here a list of things that can make period property cellars damp:
> repointing joints with cement mortar
> ground levels too high
> non-breathable materials on the inside or outside e.g. cement renders, cement plasters, masonry paint.
> air vents from cellar not far enough above ground - since cellars are below ground the air vents/bricks will always be close to the ground. Make sure there is a good gap between the bottom of the vents and the ground so that rain water cannot run in off the ground.
> A lot of cellars on older properties have concrete floors put in which is bad as it seals the floor and drives damp up the walls.
> Poor ventilation. Cellars need really good ventilation. That doesn't necessarily cost a lot either. We have a couple of humidity controlled extractor fans (£80 each). These automatically come on when the humidity reaches a certain value. If you have plenty of air brick vents then the drop in pressure from the extractor fans removing the humid air will drive fresh air in quite forcefully through these vents. We also have a whole house dehumidifier (can extract 25L per day) which cost £180 which we use if it gets particularly damp. You can of course have more elaborate systems like in line fans which bring huge volume of fresh air in and warm the air as they do so.
What signs is there that it is wet? patches? how wet is it> running water off the walls? running water on the floor? Always good if you do get a heritage surveyor to get them to carry out a calcium carbide test. This is where they drill into the centre of the brick to see the percentage of water in the brick.
Potential solutions:
Depends on the problem and how bad it is:
> If there is lots of water running off the walls and going onto the floor a membrane damp proofing course with a sump pump works very well for period properties. It is fully permeable and directs the water away from the walls and into a storage unit where it gets pumped out the cellar. However if the walls are not that wet it can be a bit overkill and not necessary.
> If there is lots of water getting in from the exterior you can have things like French drains installed so that water is diverted away form the exterior walls.
Hope that helps.
