Basements, Cellars And Brick Waterproofing
The options for applying brick waterproofing in an existing brick built basement or cellar are cavity drain, or cement renders and slurries.
What to look for in brick basements
The walls will very likely be friable due to sodium chloride in water evaporating from the walls. The brickwork can be soft, spalling and laid in Lime mortar. It is often heavily contaminated with salts. This contamination completely rules out any previously applied brick waterproofing efforts such as cement renders, epoxy, or cement coatings.
Lime render is an excellent traditional method of plastering when we consider the brick waterproofing techniques at our disposal. We will always advocate lime to encourage a building to breathe however, it is totally unsuitable for earth retaining walls. The walls will breathe for a short period of time but after that the lime will discolor and capillaries and pores will be chocked with salt left behind after the evaporation of water from the wall.
This will lead to further issues with damp as salt is hygroscopic (will attract moisture).
All applied brick waterproofing finishes rely on the strength of the substrate which in a brick building is normally a weak lime mortar joint and soft brick.
Sometimes the walls appear dry, however, that is likely to be because moisture is evaporating from the surface. As soon as you apply plaster and finishes they will appear very damp.
There is always a risk of flooding in this type of basement.
You have to design brick waterproofing for what could happen and not for what has happened historically.
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The only suitable brick waterproofing system for brickwork basements and cellars is a cavity drain system
The cavity membrane will not damage the substrate and is de-mountable so more likely to be acceptable to conservation officers.
It does not require much preparation and will accommodate normal movement.
You do not need huge amounts of preparation for cavity drain and it does not rely on the strength and integrity of the substrate.
It can be finished with any plaster or dry lining system so can be redecorated as soon as dry. Cement based systems have to be left to dry for many months before decorating.
Cavity membrane is quick to install, less mess and should be less expensive than any properly installed cement tanking system.
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We Design, supply and install. There's no split responsibility with MacLennan.
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What else do you need to think about when waterproofing a basement?