Redbeard

Possibly a bit thin, as shown in your pics. Thinner than I'd do, but then I trowel on, not brush, so can get it a bit thicker in one pass. Don't assume that just because you have a VCL you don't need a condensation risk analysis. VCL works well with assumptions that all moisture in a wall comes from the room, and also assumptions that the VCL is perfect. Neither case necessarily applies. EDIT: Was typing that while @Iceverge posted. We are in agreement re VCL. (Perhaps less so re WUFI, which has done well for me).

The plastic sheet IS the vapour control layer. It sits on the warm side of the insulation, immediately behind the plasterboard (or wood-wool or wood-fibre - choose your weapon!). These days I prefer intelligent membranes, which are reckoned to be completely vapour-closed in cold weather. (well, so is plastic...) and somewhat vapour open in warm weather (plastic isn't) so in my view it is a 'pessimist's membrane- (i.e. It should be 100% vapour-tight, and no let any vapour thro, but if you take the view that few things are guaranteed to be 100%, if any w.v. has got thro it can 'breathe' back out in summer.

I do not have reference reading for you, but at the moment that wall between the hallway and the garage is giving some restraint (resistance to 'wobbling') to the front wall. If your new door is as tight to the front wall as it appears it might be there would be no right-angle 'strutting' to the front wall.

EWI-grade Rockwool, yes. The adhesive is usually cement-based (I used EWI Pro). It allegedly has 'some breathability' but I have no figures. Given that I would not trust the adhesive alone, for EWI and for 'straight-to-the-wall IWI' you use hammer-fixings (Ejot or similar), so no reason why you could not use them here too. I have not read back through the whole thread, but why do you even need studwork? Is it already there? Is the wall 'wibbly'? Edit: Looked at the pic: No, the wall is not 'wibbly', therefore more than ever I feel you do not need the studwork. I have no experience of IWI with rigid Rockwool, but others may. Subject to a condensation risk analysis I do not see why you could not use it like WF. Can't remember the density but go to one of the EWI suppliers' sites - it'll be on there. Your parge coat at the thickness shown may perhaps crack and thus not be airtight, but as long as it is airtight I would just 'butter' the back of the WF boards with lime plaster with a 10mm toothed trowel and push it on', followed by the mechanical fixings described.

Note that (unless stone was at great risk of becoming moist) I would not necessarily have been suggesting membranes if I were suggesting rigid (140-180kg/m3) WF. Flexi WF is about 50kg/m3; a different proposition and with a great deal less scope for moisture buffering. I was, however, not suggesting rigid as the stone sub-strate seems v uneven. What max depth do you think a parge coat would have to go to to flatten those walls? Hard to tell with photos. sb1202 said: "Is the solution this - breathable vapour barrier on the cold side, 50-60mm insulation between the battens then a breathable vapour barrier on the warm side, plasterboard and breathable paint?" The membrane on the cold side (if required) would not be a VCL, but a breathable membrane ('gore-tex for buildings') rather like roofing membrane). The inner membrane is an Intelligent VCL (such as Pro Clima's Intello). Final finish for me would be lime plaster on 20mm rigid WF or wood-wool ('Heraklith')

Seem to have lost the 'quote' function: OP asked why membrane on cold side and whether it would trap moisture. I had said: ''+1 for WF, but the existing structure will make it difficult for you to get a membrane on the *cold* side between the stone and the insulation, I think. It's ar*e-covering, but I would not want to risk moisture in the wall being 'wicked out' by the insulation. I would use flexi WF with a lambda of 0.039W/mK. Get one of the merchants who offers them (I am not sure Mike Wye does) to do a WUFI dynamic condensation risk assessment. Knowing nothing of your building I'd guess that 100mm maximum would be deemed 'safe', and possibly as little as 60-80. Intelligent VCL (e.g. Pro Clima Intello) on the warm side. Then plasterboard, 20mm rigid WF or 15mm woodwool. The membrane would be breathable ('Gore-tex for Buildings') letting the building breathe out but keeping *liquid water* at bay. Yes, it is for a worst-case scenario, but worst-case scenarios are why sometimes work has to be undone. 100mm is not the gap, as queried, but the suggested maximum depth of insulation. As stated others may be even more conservative and suggest 60-80mm Thanks, @lookseehear, that's what I was saying. Remember that when you add or replace a layer to a thermal element (any bit of the building fabric which gives onto a cold outside - such as walls - or even a cold space - such as a ventilated roof void) you are within the remit of Bldg Regs and have either to meet the target U value (0.3 for walls) or come up with a jolly good reason why you cannot (interstitial condensation risk in this case. (Sorry, that's English Regs - I have just read that you are a former croft. Not sure of Scottish regs just now. I would normally do a parge (air-tightness) coat of lime plaster over the wall (when I am doing rigid wood-fibre), but your wall is a lot more uneven than a brick wall (e my suggestion for flexible insulation between/behind studs) , and it does seem to be well pointed (is it sand/cement, though?), and if you do a breathable membrane (taped at all joints and perimeters) there would be less need.

+1 for WF, but the existing structure will make it difficult for you to get a membrane on the *cold* side between the stone and the insulation, I think. It's ar*e-covering, but I would not want to risk moisture in the wall being 'wicked out' by the insulation. I would use flexi WF with a lambda of 0.039W/mK. Get one of the merchants who offers them (I am not sure Mike Wye does) to do a WUFI dynamic condensation risk assessment. Knowing nothing of your building I'd guess that 100mm maximum would be deemed 'safe', and possibly as little as 60-80. Intelligent VCL (e.g. Pro Clima Intello) on the warm side. Then plasterboard, 20mm rigid WF or 15mm woodwool. What about the window reveals? ''Floor is concrete/dpm and chipboard on 50mm (battens??) and not insulated'' . Is that to come up and be insulated? Could do a floating floor and lose the thermal bridge of the battens, and get tight insulation-insulation contact between floor and walls. **Ah, sorry, just re-read re UFH. How much insulation underneath. Remember the greater delta T at the floor level. Don't forget to ensure the wall ins touches the roof ins too. Any egg-sucking tuition is not intended!

I have not used K118 but I have used Gyproc Thermaline Super, which is a phenolic board bonded to foil-backed phenolic insulation similar to K118. If, like the Gyproc board, the Kooltherm K118 has foil on both sides (as I am sure it does, otherwise it would be banana-shaped) then you could argue that it has a VCL on the warm side. But when you put 2 boards together where is the VCL? For this reason when I was using petrochemical boards I preferred to do a lime parge coat on the wall, approx 6mm min thickness, then use the 'raw' boards, taping all the joints and perimeters (I used hi-spec air (and vapour-) tightness tape, not cheap foil tape. Then battens then plasterboard. I would go with what you describe as 'manic'. You cannot have too much attention to VCL tightness. Note I used battens on the warm side, not the cold side.

Hoo-bl***y ray!!!! I have had some worrying times but I cannot begin to think what the prospect of 'losing' £130k would have done to me. Now BREATHE! (And God Bless the LA).

21 Degrees is the new name for Green Building Store.

I don't know the relative SD values, but 'Contract Matt' is effectively designed for painting walls which shouldn't be painted yet.

''So basically I still need to know which you'd pick out of these if you HAD to: ! The M-Fires Tinderbox Medium The Ecosy+ Hampton 5'' Sorry, neither! If I installed another WBS (which I won't, but that's a long story and I agree with @Iceverge's exhortation) it would have an external air supply for sure. I'll dip out.

Your stove needs so much air to burn safely, wherever that air comes from. The 'normal way' is either a fixed vent in the wall, of a given size, or to assume that all houses leak air like a sieve and that therefore enough will be pulled through 'gaps' to satiate the stove's appetite for air. That means that when the stove is lit it will be exerting an active 'pull' from the gaps in the building fabric to the stove. That's skirting-board and floorboard draughts being whipped across your toes etc. etc. from almost anywhere in the room - an effective cooling system while your upper body toasts. If you do not have a dedicated air supply duct to the stove's combustion chamber you could still put a ducted air supply close to the stove, so that the 'route' for cold air from duct to stove is as short as possible. A raised grille set just next to the hearth and ducted below the floor and out to atmosphere would do the job. However, a room-sealed stove with its own air supply (as, for example, your modern gas boiler would have) is the best option. As regards your house being a terrace I am sure you can still duct to a spigot on the stove - it's just a longer duct under the floor to the front or rear. Ventilation generally is covered in Approved Doc F of the Building Regs and Solid fuel appliances (and ventilation provision to them) is in A.D. J. If you know all this already, please accept my apologies. EDIT: I was typing while you posted yours above. Given the price-range you give I take it you do not need a flue liner. That (professionally installed) could add a lot to the cost.

Welcome to Buildhub! Sounds fun. Belt and Braces is good, and mistakes are learning opportunities.

Double post

You need a heat-loss calculation. Your SAP assessment should help when it has been done.

Welcome. I was going to suggest that you look to stay in a holiday let built of straw (I remembered one in - I think - E. Yorks) but I find from a search ('strawbale holiday let') that there appear to be several of them (or maybe just a lot of agents 'selling' the same place??), including a couple not far from Fort William. Do you want to do load-bearing or timber-framed? There are arguments for and against each approach. I take it you already have Barbara Jones' book? There's a PDF of an earlier draft around too at https://baubiologie.at/download/strawbaleguide.pdf.

You don't mention the 2nd membrane, above the insulation. Will you be using the DA membrane as suggested? I think I would use Intello Plus instead of the DA, but otherwise I support the system. No combination of membranes will make up for inadequate sub-floor cross-ventilation, so sort that first. Before this Best Practice recommendation came out I used to use generic roofing membrane as the under-layer and as far as I can tell it behaved OK.

There are firms which offer closed-cell, and those which offer open-cell. Icynene is open-cell, I gather.

I always shiver slightly when I see PIR used (v rarely) as EWI - a few 'Grand Designs' have had it on TF construction. Some degree of breathability is desirable, and 2-4 sheets of foil will militate against that more than somewhat. Would be interesting to model where the dew-point will be, but we also do not know yet whether it is heated, or really a 'shed', with no heating. The insulation strategy suggests the former, not the latter.

+1. Is there anything quirky about the outbuilding? Less than 1m from a boundary, for example? Still no reason not to approve it, but I wonder if they have other considerations (of which they have not told you) than the amenity space. I take it they will not discuss the matter with you? Were there any objections? Also have they defined what amenity space they would like? I imagine not. Basingstoke and Deane Residential Amenity Design Guidance (2012) says 50m2 for 1 & 2-bed and 60 for 3B. I looked to see if that was net or gross and it appears net, so your shed's footprint would be deducted from your total amenity area to give the available amenity area AFAICS. BTW I am not assuming you live in B & D; it's just the first one which came up. Do any other houses on your dev'pt have sheds?

I can see that the board supporting the flashing has been wet, but does not appear so now. I cannot see the rotten rafter end to which you refer. Despite being rotten does it now appear dry? That would support your suggestion that the ingress may have been fixed. If you can get to the rafter end splice on a new piece and cut out the soft end and then, if it ain't broke, don't fix it. Just keep a watching brief during any wet periods in case any past leak recurs. I had a similar issue when I first moved to my house. Sorted the lead-work and decades later it's still dry.

Trowel more reliable in terms of uniform (and 'useful' -from an air-tightness point of view) thickness, I feel. I have never done parge costs with a broom, though.

Further variables: Heated or unheated? Is the roof oversail big enough to accommodate 'EWI'. If not you need either to re-roof or 'improvise', and the latter is not necessarily good. Good point. @Iceverge, thinking about your lay-up. The ventilated cavity is formed by the 25 x 75 battens, yes? What insulation had you in mind, or just any rigid insulant?

In the circumstances I think losing them in the first place, as I usually do, is good.