The way I've seen it done in Germany, some time ago mind, was to dig out the wedge lay the suitably insulated DPC'd raft build the blockwork wall,-some distance off the sides of the excavated hole, waterproof/tank the exterior, tied into the raft DPC, then insulate then geotextile then backfill with French drain around. The stuff they tanked the exterior was quite similar to flashband but on 1M rolls it was literally stuck to the primed blockwork. The thick exterior insulation was a type of EPS/EWI but seemed to be impregnated with bitumen. In the UK I'd be tempted to bring in a specialist firm for the job and hopefully with it the guarantee.
The idea of building into a slope is great though, with lots of interesting design possibilities, good luck.

As it's a simply shed I'm hoping to keep the design and execution simple, blockwork walls, exterior cladding, slate roof (to keep the planner happy). The ground is mainly limestone with a thin cover of soil so is stable and requires little retaining.

<blockquote><cite>Posted By: Nick Parsons</cite>I distrust tanking and tanking-type solutions so much that I would rather build a retaining wall and then build an 'ordinary building' 'on the flat'.</blockquote>

Second that ...

I guess the water table should be considered, bottom of a clay valley oozing water versus near top of hill in chalk?

Triassic - I did a similar thing about 30 years ago in my previous house. We built a new garage alongside the old one and turned the old one into a utility room and workshop. The LH wall of the new garage was a retaining wall. The garden was mainly clay which supported itself when excavated even though the "cliff face" formed was about 6 foot high! The retaining wall was built of concrete blocks laid on their side as it were, so as to form an 18 inch thick wall and we left about a 6 inch gap between the wall and the clay "cliff face"; a french drain was laid at the bottom of the gap below DPC level; the inner skin was blocks laid in the conventional manner to form a 4 inch thick wall and we formed a 2 inch cavity between the two. We used about 1000 blocks as I recall!

The back of the retaining wall was treated with black bitumen paint as it went up. When at the required height we put corrugated PVC sheets vertically behind the retaining wall and filled the gap with 20 mm gravel. The top of the PVC sheets was covered by lead flashing.

We never had any trouble with damp; note: we lived there for about 23 years after doing this work.

Posted By: Triassic

Posted By: Jeff BThe back of the retaining wall was treated with black bitumen paint as it went up. When at the required height we put corrugated PVC sheets vertically behind the retaining wall and filled the gap with 20 mm gravel. The top of the PVC sheets was covered by lead flashing.

I like the idea of the PVC sheets and gravel drainage, oh and not forgetting the bitumen.

Just a thought, where does the insulation go in a semi-basement concrete floor and walls - inside, outside, between?

Sorry, I don't know what you mean by semi-basement concrete floor and walls?

On all the ones I've seen the insulation is exterior and is part of the overall waterproofing/tanking layer.

Would this be any good?

http://www.tidl.ie/files/Foamglas_Wallboard_Underground.pdf

As someone said to me in another thread, be careful your Floating Floor doesn't become a *floating floor*!

You say EPS over VB. Assume you mean DPM, as the VB would be on the wrong (cold) side.

Nick

Posted By: Nick ParsonsAs someone said to me in another thread, be careful your Floating Floor doesn't become a *floating floor*!

You say EPS over VB. Assume you mean DPM, as the VB would be on the wrong (cold) side.

Nick

Nick - actually I should have said VB above and below the EPS, which is what I did in our chapel building recently. Belt and braces approach with the benefit of eliminating the possibility of T&G Weyrock squeaking when walked on. It worked!