Damp-proofing cellar - anyone had experience?

1 Sep 2004
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United Kingdom
I've read, with great interest, a lot of very informative posts about suggested methods of damp-proofing cellars / basements. Does anybody out there have any experience of having actually completed such a project? I know it's tempting to have a look on diynot.com for an answer, go off and do the suggested work, and not report back on your results.

I've got a 3.5m x 3.5m cellar which I use for storage. Unfortunately, it is damp (not flooded damp - I have a sump pump in a pit to prevent that) and some of my stuff has been damaged (slight mildew on furnishings and warping of paper/pictures). I found a product, Waterproof Mortar, by Hanson sold under the Supamix brand, which claimed to be the ideal solution when rendered onto the walls. Unfortunately I can't find anywhere that stocks it; I could order it directly from Hanson, but I'd have to buy a whole pallet-load! Does anyone know of anywhere stocking this? I've tried all the usuals - Wickes, Travis Perkins, B&Q, Keyline, etc.

I don't want to use a bitumen-type coating, because I would probably die from the fumes, using it in a confined cellar!

I've also read o these forums about SWS slurry. Has anyone out there had experience of this? With good/bad results? This sounds like it could be the answer to my prayers.

The external house/garden drainage is fine.

Many thanks in advance! :D
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Most houses with cellars are old houses. Old houses were built to designs that required the house to be able to "breathe".

If you have problems with damp, the first thing to check is ventilation. You don't want to go rendering walls with waterproof coverings, that will just be hiding (and possibly compounding) the problem. For example, can you see where there used to be a coal-hatch? It is likely this has been bricked up. That would have been essential to ventilate the cellar, so alternative vents will need to be installed (if they aren't already there)

Now, if you are just going to use the cellar for storage then ventilation is key. You need loads of it. Air flowing in one side, and out the other. The cellar will dry out over time. It might be a bit colder down there, but that is what you want from a store-room anyway. :D You can get breathable paints that are ideal for painting cellar walls (after they are dried out, of course!). A mate of mine did his cellar recently, the paint was some very specialised stuff that cost shedloads of money.

However, if you are planning to turn it into a room afterwards, it is a whole different matter. This really is an area where you need to get a specialist to work you out a quote. It isn't as cheap as just rendering the walls and putting down some carpet, but you will know that in a couple of weeks you will have a proper habitable room, complying with regs, with no damp smells. And you know if it starts to go mouldy or leaks, then you have a guarantee you can call on. And it will also allow you to sell the house as having an extra room. Which you can't if the building inspector doesn't sign it off as a "proper" conversion.

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