Questions regarding Foundations, Slab and DPC for outbuilding

[plunketyplunk]

Hi,

I am looking to build an outbuilding on the boundary of my property. I'm on a hill (with ground raising to 1200mm on 3 sides) and to maximise the internal headroom whilst maintaining the max overall height of 2.5m I intend for the internal floor to be about 300mm below the level of the garden)

the walls will consist of 2 x 100mmm high density concrete block with a 100mm of acoustic insulation (R45).

The image below illustrates my thinking in terms of the structure. I'm particularly keen to understand if I'm in the right ballpark regarding the DPM, DPC and the Foundations. I'm hoping that someone can give this an eyeball and let me now if I'm over/under engineering it, missed anything or even got something totally wrong>

Any guidance would be greatly appreciated.

Ben

 

[George_engineer]

There's a very easy route for water to enter through the cavity wall.

You need to have at least a ventilated cavity below ground level, or if significant water is anticipated, a drained cavity.

A max retained height of 1500mm will mean you need help from a structural engineer (Part A allows only up to 1m height difference). They can also assist on drainage

 

[Notch7]

With ground level being 1200mm above internal floor level, the damp arrangements need to be more in line with a basement construction

 

[plunketyplunk]

thanks for your answers @Notch7 & @George_engineer. I will indeed consult a structural engineer.