Tony
I'm 36 and this will be the last house I ever live in. I've designed it so it can be extened in two directions to increase the size of the living area and add a bedroom and bathroom easily. Infact, it was designed to be larger, and then trimmed back to what i'm actually building now.

I have to get the materials right now for where building efficiency will be in 20 years time, so maybe 0.1 Uvalue walls from the get go aren't a bad idea....

Posted By: TullichDoes anyone think it would be worthwhile splitting this into two threads, one for floor construction and one for wall construction?

I doubt it at this stage. With hindsight, it might have been better to start two separate threads originally, but I think most people on here read most threads and will join in if they have anything to contribute.

I'd suggest that the next thing to do as regards the floor is to contact a few engineers that specialise in passive slabs and see what they have to say about what's practical and what the likely costs are.

Probably similar for the walls, but you've more chance of getting a supplier to provide the condensation calcs etc as part of their supply, or their bid for supply.

I'm probably not understanding your design approach, but as regards structural engineers, I think I saw you mention that you have a SE on board already? I'm guessing he's from the timber frame company, as you mentioned the need to get another SE to cover the entire build (foundations AND frame), which would be correct in that case.

If you get a specialist SE who does fully insulated rafts, you'll need to be sure he also will cover (or do an SER for) the whole building, or you'll need a 3rd SE...costly, and very confusing as to who has what responsibility.

If you're still unsure about ground bearing/solid slab versus suspended, one thing that might help make up you mind is (as has been mentioned a few times) the fact that the finished floor level will be much higher for a suspended floor as opposed to a ground bearing...like 300mm higher, assuming you don't want the solem to be below external ground level. Can you adjust scaping to allow for that? Probably need a planning amendment at some point to cover that.

Also, building over the winter (as your timing suggests - design, warrant approval, start maybe Nov if lucky), likely the suspended timber floor will go in as the first stage, prior to the frame...keeping the floor joists and it's insulation dry for a couple of months would be challenging.

Ok, so that's not very helpful in terms of moving you forward!!

So here's my tuppence worth, as someone who designs and builds low energy houses in the Highlands...keeping it simple in terms of who you can get to do the work, and supply materials, rather than just looking simple on a piece of paper...

- strip foundation, prob 600 wide, 200 deep, at a depth of around 600mm below grade, steel mesh on bottom.
- blockwork underbuild (could be 100mm if not doing 140mm frame)
- 150mm compacted type 1 solem
- DPM over sand (are you in a radon gas area - check)
- 300mm EPS70 with 50mm kingspan vertically against the inside of the block underbuild
- second DPM over the EPS, mainly to stop the water from the concrete running through the EPS gaps
- steel mesh set on stools with 80mm top cover
- cable tie your UFH pipes to the mesh (if you want UFH)
- 125/150mm C35 concrete
- timber frame (can be 100mm don't need 140mm structurally)
- walls; plasterboard/25x50 battens/VCL/rockwool/OSB/125 PIR/battens/cladding
- add 100mm EPS on ext face of block underbuild and render it (use your offcuts from slab)
- roof; plasterbaord/25x50 battens/VCL/300mm JJI/full fill with wool32/22x150 sarking boards/highly breathable membrane

Lots of ways to skin a cat (sorry PETA supports), but the above will be understandable by any SE, most contractors, BSO's, gives Uval 0.1 or very near, no condensation, no cold bridging so very low psi values for your SAP calcs, and something you have half a chance of getting started this year.

Posted By: GreenPaddyIf you get a specialist SE who does fully insulated rafts, you'll need to be sure he also will cover (or do an SER for) the whole building, or you'll need a 3rd SE...costly, and very confusing as to who has what responsibility.

Could you explain that a bit more, please? I had one engineer for the foundations (Hilliard Tanner) and one for the wall structure (Paul Rose). Neither of them took responsibility for the other's work AFAIK and that didn't seem to cause any problems. FWIW, supplier's SE was responsible for the metal-web joist 1st floor and yet another SE was responsible for the curved timber frame roof.

Hi Both,

I have a very red face this morning....

I'd never actually discussed the raft/slab idea with my SE, assuming (incorrectly) that it would need seperate specialist input. Turns out he's done dozens of them and, what's more, he's confident he can engineer a diyable solution that doesn't use proprietary forms for the edges. It's looking likely that we'll have a bespoke solution shortly using standard sheet EPS and some clever shuttering.

I'm incredibly excited. Updates to follow.

Posted By: GreenPaddydjh - If using an SER, then that struct engr checks all the calcs, loadings etc, so it's bound as one design. It may be different in England

I don't even know what an SER is, and a search finds 'SER Scotland', so yes I guess it is different in England. For that matter, Wikipedia doesn't know what it is either, so it seems to be a closely guarded secret.

Seems like good idea at first glance though.

Ah, there's an explanation at http://www.aed.consulting/design-certification-ser-certificate/

edit: Tullich, that's very good news. Hope you make rapid progress now.

Residential
Exterior
Membrane
Outside insulation
TEchnique

Slightly tenuous, but good to give a build type a name I think! The video series whilst looking a bit dated is excellent for the self builder. Take a look at CCHRC's "Integrated Truss Frame" (roof truss manufacturers in this country take note of the potential to expand into this area!) and the adjustable piles/steel ringbeam they use in lieu of conventional founds on the Tundra. Excellent stuff.

In a similar vein there's also the PERSIST wall:

Pressure
Equalised
Rain
Screen
Insulated
Structure
Technique

Oh, along with Matt Risingers "Perfect Wall" as seen on YouTube.