ok crazy idea, but im thinking of building a new shed and the bottom couple of foot would be below ground with a concrete base and brick wall around up to ground level so i could gain mor internal height but the shed would not appear tall.id rather not have an air space around the shed to keep it dry as its a waste of what little space there is,so what would need to be done outside the brick part to prevent the bricks becoming wet overtime if it had earth up against it.what would be used and how is it done?
Engineering bricks.
Engineering bricks might be a partial solution but are they not primarily designed to be frost/fire resistant and take structural forces? I'd suggest you need a water proof barrier e.g. a waterproof membrane.
Tanking
Yep, Tanking.
tell me more about membrane? is that just another word for very thick plastic sheet? is the whole thing build in/on what is effectivelly a pond liner?
and whats tanking?
Tanking, in simple terms, means the installation of a waterproof membrane to make the area impervious to water.
To just say "you need tanking" is a little dumb as it's a word for a goal in construction not a product. It's also what you would call waterproofing the walls in a shower but using a different method.
There are several methods you could use something like Vandex can be applied to the walls / floor internally once built. This is ideal for waterproofing an existing cellar or similar.
The other option is to apply a membrane to the external block work during construction. Different products have different application procedures and requirement but look at something like RIW Sheetseal 226.
the key question is how waterproof do you want it?
cheep are cheerful - paint the wall and base with loads of blackjack prior to backfill. prone to leakage after a time
less cheap - poly sheeting. under the base slab and brought up the sides of the shed. its important you do under the shed otherwise it wont work. the poly sheet should be solvent welded at the joints to ensure its watertight.
you can put in a cavity as per house construction but this is more expensivce again and you still need a DPC
Vandex (a waterproof concrete screed trade name) is Ok for existing basements but you wont be able to fix to that area vandexed and also if you have a high water table it can leak as the water pressure pushes it off the wall.
engineering bricks wont work. the mortar is permeable too.
oh - the poly sheet wants to be tied into the DPC in the brickwork above ground level. you may want to face/hide the poly sheet externally to prevent accidental damage in the futeure as it will be a bugger to fix at a later date.
so basically the poly sheet means nothing outside the building can ever come into contact with the bricks below the dpc.
I live in a very old house (160 yrs) with a much older cellar (probably 250yrs - I guess it must have taken them ages to get planning permission). The cellar tends to flood when the water table rises.
A surveyor warned me not to get the walls tanked as if the water table rose it might blow the cellar walls in.
Waterproof concrete faced externally with some form of tanking membrane.
Think ££££'s