Redbeard

Welcome! Judging by how much of the purlins (horizontal beams) I can see it looks like no extra depth has been added at ceiling level. Therefore if we assume the rafters are 75mm (they might be 100, but unlikely more) then, if a ventilation gap of at least 25mm (50 is better) has been left between the back of the tiles and the insulation, you will have 50mm of insulation at best, if PIR (polyisocyanurate - Kingspan or Celotex-type insulation) has been used. If no vent gap has been left you may get moisture issues (wet roof timbers) and if you wanted to comply with Building Regs (which for a loft conversion you have to) you would need 150mm of PIR, not 50. As regards the additional timbers you had fitted, everything depends on whether they were specified by a structural engineer, and whether they span from brick wall to brick wall (as additional supports) or are simply fixed to the sides of the existing joists. If the latter then they may have added minimal extra strength, but added extra weight for the original joists to carry. I am not a structural engineer, but you need one, and no doubt one will be along soon. As to the dormers, probably no problem in principle, but I am not sure whether they would be Permitted Development (i.e. you don't have to make a Planning Permission application) or not. I've no time just now, but search 'dormer windows - Planning Permission/Permitted Development and you will find guidance. Most of all: Will you still have room to stand up when (maybe) the floor has come up in height and the ceilings have come down in height?

I cannot be quite sure of what I am seeing here. I can see a black membrane under the OSB (which I take to be the bottom of the 'Warm Roof Sandwich') but I cannot see the detail of what happens downwards of that. It looks like there could be a gap between the roof 'sandwich and (???) a false ceiling below (???). Given what I cannot see in the pic could you sort of 'talk us through it'? Cheers. Edit: As @markc says above "you definitely don’t want your cold roof ventilation going under the insulation of the new bit". From what little I can see it looks like this might be the case. I hope not.

Are you doing all the work yourself? I am not sure where the £40/m2 for EWI came from, even at only 50mm. The '+' must be a very big +! For years 'around £100' has been the regular cry and it very rarely comes in at that. Including 'enabling works I have seen it well over £160/m2.

Just seen @ToughButterCup's post and reference in this thread too. Very clear.

Perhaps we can agree on another term for a roof with insulation all above the rafters? I wrote: and @scottishjohn wrote: If we change the 'title' of 'my' description (only 'my' in terms of my having used it above) to 'Warm Roof *Structure*' - meaning one where all the supporting timbers (or steels or whatever you like) are 'tucked up warm' below the insulation layer I think we've cracked it and avoided confusion. This means we can then also have a hybrid 'Warm Roof Structure' where some of the insulation is on top and some between the rafters. Thoughts and comments welcomed.

It's essentially a cold roof over room(s)-in-the-roof. A Warm Roof has all the insulation *above* the rafters. Whether or not the roof void is used as a room or just a cold void does not necessarily change whether it is a Cold roof - it is simply a Cold Roof on different planes. Then we can get onto hybrid Warm Roofs and interstital condensation risks, but we won't now!

Would you have wanted to change your current (soakaway) arrangement anyway, due to the drainage not being good in your clay soil? Or, if the house had not been built would you not even have thought of changing the status quo? You say: So you sold the land to the builder? With Planning permission? Which you arranged? If so then the position of the house on the site may have been set by you or your designers, in which case it would have been clear that the minimum 5m distance between soakaway and the new house may not be achieved. (I see @Mr Punter has just posted, so I'll stop now and see if we have said the same thing!) Edit: No we haven't!

Others will come along with different views and 'recipes' but I am a great believer in rigid (and in fewer cases flexible) wood-fibre as a solution (as both IWI and EWI)for older buildings. Many more details on request!

A metal fabricator will make pretty well anything you want assuming they have the right equipment. I have used edge trims and extension cills in white anodised aluminium. I got mine via an EWI supplier but they were made to order by a metal fab'r. Check out your local fab shop.

Welcome! In no particular order, you say: Does this mean the windows we see in the pic are replacements? If not I would consider giving the bay plinth a long hard look. It may be the photo or my eyes, but that brickwork looks like it has 'drooped' somewhat. Yes, one can argue that in doing so it has 'found its position' but given that it appears there is a lot of raking out and re-pointing to do I sort of wonder how much harder it would be to rebuild off a new footing. Of course I don't know what is on the outside, which may also have a bearing on your decision. Again, all this assumes that the windows are not new, and will be replaced. Ignore me if that is not the case - there are other ways of skinning this cat. Re lime mortar I might be looking more at lime putty rather than NHL but I am not a lime expert, just someone who sometimes uses it.. I have no idea where he is in relation to you but you might try Nathan Goss, who teaches at the Centre for Alternative Technology near Machynlleth. For external walls can I fly the flag for a lime parge coat (air-tightness layer) even if you do decide to batten. If you have not stopped all the air movement then 'hollow' finishes may simply become something for cold air to move behind. I am jumping forward to something you have not even mentioned yet but can I assume that you intend to insulate the external walls, either externally or internally. External is arguably much better (and 'safer' from a moisture point of view) but now, when you have the plaster off, is the time to make the call on whether you insulate internally or externally. Good luck with the 'project'. Loads to have fun with!

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