JamesP

That is an image from google. I battened then counter battened before fixing cedar. Only 50mm gap here. I assume you will use larger timbers. I think it most cases the timber frame would have been designed to accommodate the overhang. Can the gable end fascia / soffit fit the extra 200mm?

From a practical point of view running the cladding proud would help keep water off the top of the stone work and clean edge. Do a quick search, mostly forward of stone work. Lots of great examples.

I would be inclined to run the cladding above the cill height as the horizontal line would be very dominant.

I did tape all OSB joints as well. The VCL was fitted to the timber frame using double sided tape. This was to prevent the warm air migrating to the insulation. All works well, have been using about 1200 - 1400kWh per year for heating in a 275 sqm home. Mild winters though. We can cope during the day but night was a challenge. Would consider Solar glass and external blinds next time. The AC is great especially if you have PV. Perfect timing from Gus, On top of the 200mm rafters I counter battened 70mm C16 to then fix the Fibre board and add another layer of insulation. Every external wall and roof had 11mm OSB fixed on the inside before batten and plasterboard. That was our racking layer.

We have a metal seamed roof so on +25c days we overheat in the summer months in the 1st floor bedrooms, I think mainly because we have zero shade and the building gets 16 hours of direct sun during the peak summer months. I plumbed for AC. We have T&G fibre board over both roof and walls, would not build any other way now. I put the VCL inbound between the insulation and OSB, lot of attention to detail and plenty. of airtight tape.

Similar warm roof build up to mine, though have an additional 120mm insulation and 11mm OSB( for racking) instead of your 30mm PIR. I would avoid Multifoil, I saw some after installation in a new property and it had sagged and no mass. I also would not use PIR between the rafters, never seen a decent fit. Steico, though costly are great products.

We were in for 3 years before private BC got pushy. Just go for it. Have a read :

+1 for airtight tape. Worth spending some time and money on covering all holes. https://passivehousesystems.co.uk/shop/airtight-tape/gerband-586/ No comment on "a contractor".

From memory I probably allowed 25mm on each side as I then fitted Pavatex 20mm reveal board around all openings for windows.

@Bramco That is a fab project and build, the flush roof lights very smart. All our triple glazed Velux are on the 1st floor, bedrooms, bathrooms and landing with fitted internal blinds, just about accessible if you are 5'9" +. Would consider solar glass or external blinds and in hindsight have the large fixed window at the gable end opening. 2 in each bedroom to provide some cross ventilation but will be connecting (plumbed in during build) AC to provide proper cooling.

I used EDW for fitting 7 Velux in Tata Standing seam roof. All I can add is take your time with the detail and an extra pair of strong arms for the lift. Have a look at this for starters.

I agree @Roger440. Its a grift, the ultimate pathological altruism.

Have had a quick look and the dpm is mostly cut short next to bottom of sole plate. I would just try and protect soleplate from water splashes, also fitted rodent stainless steel mesh behind cladding. I wrapped the breather membrane underneath the 40mm pavatherm, green. I extended the Cedar 50mm below batten to protect the sole plate. Once board, 2 x batten and cladding fitted probably 75mm proud of render face. Dodgy drawing enclosed. I would not create a pocket where damp could remain in B.

Enclosed a drawing of sole plate detail on my build, not a builder but I brought the 40mm pavatherm flush with the sole plate and lapped the dpc under. Then batten, counter batten and Cedar. I would not leave it exposed. Would bring the medite board level with block and sole plate. Others will have ideas.

With a tray 1200mm is fine as @Kelvin.