How to set footings for a stepless level floor in a timber garden room.

[dai jinks]

Howdy, this has proberbly been discussed but I think I'll ask again for my own particular needs in my planning.

Like others i want to build a 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 max 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

 

[foxhole]

Do you have planning for a habitable dwelling?

 

[dai jinks]

No not yet but will have once I've submitted application and drawings etc.

 

[big-all]

keep in mind whilst sheet material is imperial timber is metric so your 8ft roof span may not work with nearly 2" missing from the joists meaning you need 2.7m timbers or 5.1s in half or plan well and use the bottom or top plate to pad out the 2400 to eight foot to give you the height on the walls

 

[dai jinks]

OK will do. The structure will be made in metric but I can also speak in imperial but that's not of importance, neither is the exact dims of it for permitted planning consent as long as everything on the plan is to size or smaller then all will be approved. Its no big deal a small end of garden hab space here in London.

I wanted comments on the technical side of setting up a level garden to the building door threshold.
Let's see. I guess blockwork to a coarse above ground (apart from the
level door threshold aperture ) will be the way to then frame out the rest of the structure.

 

[foxhole]

I would avoid same level as garden , you will be forever clearing leaves and rubbish which blows in and difficult to avoid damp problems .

 

[dai jinks]

Thanks for all this sensible advice. I'm gonna raise it for sure.
I've got a really weird question hanging around me about something else but don't know where to post it etc and it is, I've converted the loft with a shower bathroom about a metre of flat ceiling ( for door and shower unit etc) then it rakes about 30 degrees down to the from, passing by the toilet and opposite sink, leaving 2 m of rake space until the supporting wall on the steel beam for the existing roof etc.
In this approx 2m x 2 m space, am I allowed by regs to have a single bed to use now and again?
It could have a sliding barrier or similar ( like in victorian times when people slept in inclosed wooden compartments within he room occupied. Are there regs basicly to stop this practice of resting in such a spot.?
There is a velux above and the door could be changed to an fd 30.
OK just a thought.
Cheers