Redbeard

I had based my comments (as had @joe90, I think, on your post above: So 150 is the max, but due to the random wall construction it goes down to 50? I now understand why you are concerned about losing more space.

Have I misunderstood? I thought you said your studding was 150 from the wall. A reasonable gap would be 50mm, so you could get 100mm insulation in and add a service void while losing 40mm at most. If you are prepared to have wiring on internal walls only you don't even need that.

Looks good, particularly if you do not need much. Otherwise you buy 25kg NHL 3.5 and a fair old lot of sand (depends whether you are mixing by weight of volume, but crudely 25 kg, or 4 small bags from DIY stores. Fine if you need that much.

Yes, I gave the example of 'dot 'n' dab', but if there is any external air-leakage into the cavity behind the plasterboard then you have brought the 'outside inside, and potentially you could have just a half-inch of plasterboard between you and air at external temp. I was going to suggest insulation, but @saveasteading already has. I more usually used to insulate 'hard to the wall' on a lime parge coat, but fixing through granite sounds like it would be ... fairly challenging!

It describes a 'syndrome' where you get unwanted cold air circulating on what should be the 'warm side' of the wall lay-up. The most typical manifestation is 'dot 'n' dab' - plasterboard fixed to a wall on blobs of adhesive with lots of hollows between. Any air leakage through gaps in the wall may get through to those hollows - That is a 'plasterboard tent'. In your case I think @joe90 was referring to the apparently very (air-) leaky stone wall with the void betwen it and the hollow-fixed pl'bd. *Ah! I see @joe90 has just replied. I'll post this and maybe find we have said the same thing!

Possibly 3: 1 grit-sand and NHL 3.5 hydraulic lime may be easiest to get. If you have a lime supplier near you you could ask their advice. NB: *Hydrated* ('Bag-' lime) is not what you want. That is used mainly as an admixture in cement/sand/lime mixes.

Struggling to work out what bond that might ever have been. What does it look like on the outside? The reason I ask is that on the inside the RHS of the lintel seems to be sitting on a pile of bricks. I suspect that half of those I can see are through-bricks, which makes it less scary, but it still looks like it's not held together by much! In the light of this then any mortar is better than none at all, but you are right, the original is likely to have been lime. The lintel bearing would not meet today's standards but neither does that automatically mean it is 'going anywhere'.

You may find you need a surprising no. of holes. Typical 'strip' eaves vent allows 25mm of clear vent path, so 25,000mm2 for each linear metre. If doing holes a typical 70mm round fascia or soffit vent gives 2000mm2, suggesting you'd need twelve-and-a-half per m. I don't usually use round vents but when I last checked them out we were amazed how many we'd need - many more than the contractor had proposed to fit.

To what insulation standard? If it's a refurb then the U value targets are elemental - a wall needs to be this, a roof that, etc. New-build is treated differently and it's done via a SAP (Standard Assessment Procedure -for the energy rating of buildings) assessment, comparing the CO2 emissions you will achieve in your build (the Design Emissions Rating - DER) against a minimum target (The Target Emissions Rating - TER). Can you confirm what thermal standards the walls, for example, have been built back to? The extension is not an issue because extensions are assessed elementally, too, and the target is 0.18W/m2K. How about the walls which were 'existing' till they got knocked down?

I was just thinking how nice it looked, and how little the Fire Officer would like it... Edit: And then I saw the other posts below! Sorry! Been there; done that.

OK, so currently you have a site, and the party wall is temporarily a gable wall. Pictures would help but if I am right in my surmise I am not sure that you can argue that anything remains. You can argue that *your* party wall remains; they can say 'no, that's the neighbour's'. The neighbour has a house to back up their claim and you don't, as far as I can tell from your description. Or does some of the gable wall remain? You refer to a 'cleared site' which suggests not, but you refer to only demolishing the *front* wall. You could definitely plead ignorance of the rules and explain that the builder deemed to front wall unsafe (??) and 'ask for forgiveness' but in the light of @TommoUK's post I am not sure how much success you will have. Full contact; full disclosure, I guess must be the approach. Get onto the LA and explain the circumstances very clearly. I also think you and the owner probably need expert 3rd party advice. I am not sure if that's from Planning Consultant or what. I do wish you luck. This must be extremely distressing.

On the positive side that really is a beautiful 'duct-forest'! Doesn't need boxing (not that I think you were going to); it's a sculpture!

To make this more bullet-pointy see interjections* above: I will be delighted if others come back and say 'No. You could do it far cheaper than that' but really until you have 'laid it bare' and got plans done you cannot get an accurate price. Edit: Forgot re stair. To get a stair in you are likely to lose something off a 1st floor room, unless your landing is very 'generous', and because of the sloped ceilings and the need for a min 1.8m (IIRC) headroom your stair will 'chop up' the space somewhat. Basically, as far as I can see, it is going to have to come up under the ridge (in the middle of the space).

Almost certainly not. It depends to come extent on the insulation strategy for the dormer, and how far down the existing roof you have to come to get a good structural 'connection' between the dormer roof timbers and the existing roof. You need the existing ridge to 'work' with the dormers, so the likelihood is that you'll have a small bit of pitched roof below the ridge tiles (let's say an absolute minimum of 300mm), then the roofing felt/membrane (I am 'building' the dormer 'backwards', from the top!), then - if you choose a 'warm roof' with the insulation above the deck - 150-250mm of rigid insulation, then say 175mm rafters plus 15mm skimmed plasterboard, then the internal ceiling below the apex could be as much as 625 - 725mm below the very top of the ridge tile. That is like taking your 'outstretched arm' out of the equation, so if your fingers would reach 150 or 300 from the top of the space, now that would be the top of your head 150-300 (total guesswork figs) from the top. If you do a 'cold' roof, with all its possible attendant condensation issues, you could perhaps lose 100-150 of that 625-725.

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?