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Level with outside ground Foundation for garden room.

Posted: Sat Feb 25, 2023 2:49 pm
by dai jinks
Howdy,
Like others i want to build a man cave livable room and the end of the garden.
Its gonna be 2440 x 2440 x 2500 plus a small side extention same hieght for toilet and shower. (very cramped i know but doable).

I share a solid rear boundary brick wall 215 with some extra piers my side in it. ( it used to be a cavityless factory outer wall)
Its has pertruding double flat tile drip and a soldier coarse on across the top. Total 2650 high from ground. My side, there is damp on 1/3 because the niegbour has build up all sort on the other (a small high disused fish pond ).

I'm to make up off this wall a standard timber frame and flat roof.
My question is this so far;

I already have 175mm poly slabs for floor insulation.
I want the threshold of doors and the floor to be say 25 mm up from level with outside ground on completion.
I don't want to pour one big slab but rather build a 215mm block perimeter on a footing, then infill with the insulation slab to levelish with the blocks and my floor cover on top of that.
What do I need to additional do to make this level floor water and damp proof from the outside ground ( and underneath i guess) before I build my frame work on top.

Anyway thats me and my dream for this years nice weather. Any tips and guides be great.
Thanks

Re: Level with outside ground Foundation for garden room.

Posted: Sun Feb 26, 2023 10:20 pm
by stoneyboy
Hi dai jinks,
Build your perimeter wall so the blocks are one course clear of ground level. Sand blind the floor base and lay DPM on it and up the blocks. Then infill with insulation and add wearable floor on top.
You should build away from the rear wall or you will get damp issues.
Regards S