Redbeard

Hmmm... a) I share your pain! b) Maybe there is (though I am not certain for refurb) due to the feeling that mortar and gravity are not going to hold your ridges forever. I wonder if you could satisfy them if you did some clever metal strap-wrangling so that you could trap down each 'plain' end below the 'oversail' of the next. If you used, say 3mm steel and worked it hot (or got a fabricator to do so - all they need is your sketch and dimensions) this could work. But it would have to 'work' for roofer and BCO. If I had such lovely ridges I would be happy to finish that myself if BCO would accept it.

The lack of a completion cert suggests it has not been signed off! (Surely). I always received completion certs for my jobs. The heading says 'Date of Completion Cert (If issued)' and the comment is N/A. I would read that as 'It is not applicable because there is no date, because there is no completion cert', but I see that in this case they use it as 'not available'. Either way I don't think that helps you, as it could be 'not available' 'cause they lost it, or because there never was one. Of course I could be wrong....

If you go with Wood-fibre you could go to a merchant which offers (dynamic, more accurate, condensation risk assessment) WUFI for free. Building Control depts are very variable. Mine used to be quite hard to get a conversation with, so if you were doing anything with any element of doubt you just had to go with your gut and hope the BCO agreed. Since they may only do 2 (or even one) visit(s) you don't, ideally, want to wait till you have done something (based on your best researches) to get a BCO opinion on whether you've done right. They should have no problem with an area-weighted calc, and should also be OK with you not quite achieving 0.3W/m2K (0.3 with WF may be an IC risk). I used to use the WUFI calc to back me up on that. On the other hand some merchants do a cost/benefit trade-off and suggest even less than I'd use. Not sure always how you get that past BCO. My feeling re WF is that if it functions without a VCL then you don't have a VCL to get wrong. Just go tight as a tight thing and stuff any gaps with 'fluff' (cutting 'swarf' mixed with water). Always use a (lime, in my view) parge coat. Views about gypsum as an under-layer vary. As I say, I have used PIR when the client cannot pay for WF, but I'd much rather use WF.

But surely the hole will be in the right place

I am sorry you have had a rough time. I picked up on the words 'acting as my electrician'. Are they one? If it were me I guess I'd be looking at the terms of the original agreement (which might be the 'feel' of it if it was verbal). Did any particular thing precipitate the decline of the relationship? Have they done of not done anything which might be of interest to Trading Standards? Oww! 'Multiple more thousands' sounds painful. I don't know much about the Small Claims Court but is there a clear breach of what you thought they intended to provide?

If I were doing something like that I would use Pro Clima's Intello (which is vapour-closed in low temperatures but becomes slightly vapour-open as te weather warms up, allowing 'dumping' of any accumulated moisture) as VCL, not the foil on PIR, so just make the wall as thick as you need to get the U value you want without the PIR, then it could 'breathe' (a bit) both ways instead of being 'blocked off' on the inside.

Sorry, that's drivel!! Reaching the dew-point on the inside of the external wall is more likely with thicker insulation, not thinner. I know that! I think my brain must have gone on holiday for a few minutes... Oops! Try this: I would not recommend having no insulation at all in the shutter-boxes. If you can use a high-grade insulant (such as the aerogel you referred to) to ensure that the surface is warmed up sufficiently in the shutter-boxes for condensation not to occur then (though the insulation value may still be cr*p compared to the rest of the newly-insulated wall, you may avoid a local mould problem inside the shutter-boxes.

Welcome! Showing that an impermeable insulant works is generally done with the aid of a 'Glaser Method' condensation risk assessment (henceforth CRA so I don't have to type that again). Glaser method is the British Standard method, still, AFAIK. It is not a 'dynamic' tool and is a bit of a blunt instrument. Again, AFAIK, it always did assume, and I think still assumes that all moisture in a wall comes from inside (in the form of water vapour). Therefore a sheet of foil will stop all moisture and everything will be hunky dory. Each of your composite boards has a VCL. Where is the VCL at the joint? I have favoured wood-fibre (and a request for a waiver on the U value) for a long time, but if I was doing PIR for clients I would use 'raw' PIR at 50mm, taped at all joints and perimeters, battens to fix it to the wall and a further 25mm PIR before plasterboard. You have to be really picky to get the VCL right. I prefer WF which has no VCL. No VCL = no VCL to get wrong. Just a pedantic point -sorry! - you say 'high U value'. High insulation value, which is a low U value. Also, to get 0.3W/m2K on a solid brick wall you will need a board of about 70mm (60 insulation and 10ish plasterboard) so your shutters won't work anyway. What thickness is your builder proposing? Who is doing the Building Control application. (In case it has not been mentioned, you need one.) You could claculate the area-weighted U value so that you could have 'fat' insulation away from your shutter boxes and thin at the boxes, but you would need to be sure that the thin insulation would not give you a dew-point. I am not sure how that would help? Do you think your bricks leak water? If they do, they'll leak with a thin thing or a thicker thing attached to them. Re the bathroom XPS will give you a VCL (the XPS is its own VCL) which you need, unless you use Wood Fibre (which is not recommended for wet rooms). But thin board won't achieve the target 0.3W/m2K U value. I hope this sounds positive, not negative! Queries welcomed.

I have done something vaguely similar, but with wood fibre. Just stagger the outside and inside verticals and make it as 'fat' as you need to get your desired U value net of the timber fraction. In my case the external members were structural and the internals not so, but it can be either way round, or indeed the load can be shared.

Beading, mesh, render I'd normally have said EWIstore... Do you feel they are expensive for those as well as for EPS? Obviously let us know, please, if you find somewhere cheaper.

I second @marshian's comment re the chipboards weetabix/digestive biscuit. I would not put chipboard within a mile of a wet room, but I realise that opinions vary. But cut out that soggy bit, please!

How are your lungs? I would not like the idea of 'boxing up' that much mould. As I said before I don't like the other alternative (treating with effectively chlorine bleach) much more. Get shot of anything with a hint of mould on it and splice in new.

The mould-ridden plasterboard we can see - Is that the back of the wardrobe? The last 2 pics suggest that the wardrobe has its own (hardboard?) back. So has the wet got through that plasterboard and then hit the integral back of the wardrobe? Is there any space between the 2? I'd like to understand the 'mechanism'. You can either jettison the mould-affected timber or treat it with fungicide - possibly based on chlorine bleach. With that as my option I'd choose replacing the timber.

OK, I'll chip in in the light of the above. Obviously none of us (except the OP) has seen or felt the surfaces but, as it's lime, you could consider something like Baumit RK70 - maybe with mesh; it's early and I have not thought that through enough yet. First stab is yes, rather than no, to mesh. And if you want a really smooth finish (think silk gloves) use Baumit Kalkin Glatt - goes on extremely thin, almost like a polish, so the RK70 has to be good. I'm not advertising for B----t, I just used the stuff for 10+ years with great success and I am not a plasterer. Other companies do lime products that do a similar job but I have not used them enough to be used to them. I note that you refer to Blue Grit and PVA. If the existing surface is very friable then no amount of nice lime plaster is going to hold onto the wall, necessarily. If it's sound but pitted, perhaps do something like I have suggested, without 'artificial aids'. You could do a 'test piece' of both... These lime products are not generally available at mainstream merchants, but they are available easily from specialist merchants.

If you do have bigger gaps cut down each side of the joint to the base of the PIR, so you have an open V with the wide (not that wide!) part on the top of the PIR, facing you. Then it is quite an easy job to start foaming at the bottom of the V and slowly bring the nozzle up till you have filled to the top. Of course you can stop before you reach the top as each squirt expands, but knowing when to stop takes a bit of experimentation. The tape over as VCL. I prefer to use air-tightness tape rather than foil tape.

I have never used them but I believe others on here have used: https://www.daemmstoffhandel.de/de/luftdichtigkeit-dampfbremsen/feuchtevariable-dampfbremsen-73/. I don't know the practicalities, but someone who has used them may chip in.

I'm not quibbling with that as a general principle, but it was my N-facing one which 'died', not the W-facing one installed at the same time which gets extremely hot in the afternoon sun (even as I type, in early March).

Oww! Yes, definitely failed unit. I'm gloomy enough about one of mine failing in year 11 of a 10-year warranty 😞, but yes, you should be covered without question. Who installed them - you or the supplier?

Any metal fabricator should be able to make you what you need. Try EWIStore: https://ewistore.co.uk/shop/external-wall-insulation/cms-810-120/

Definitely sounds like it!! What 'mechanism' are they invoking to claim that interaction/result? Sounds like a possible boat-lifting/dropping device in an area of London in the Tower Hamlets area.

Thinks... Or are the tiles on counter-battens and battens so that the vent path is from eaves to top of wall?

But the dwg shows a ventilated void. One assumes that is to keep the timber frame 'happy'. You have not got that, it would appear, and the architect, not having seen the builder achieve what the dwg says they should achieve (a ventilated void), as far as I can see, is of the view that it's to a 'satisfactory standard'. I can accept that a cut-in flashing can be OK (though see my earlier comment re render-board and the likely depth of the 'chase') but it neither satisfies you aesthetically nor provides the ventilated void (AFAICS) which the architect specified. The 'finish' may be to a satisfactory standard (to the architect, but not to you, the client) but the 'middle' -the provision of a ventilated void - isn't there, as far as I can see from a none-too-close-up pic. Please correct me if there is some other sort of vent provision in what has been provided. Oh, and almost as an aside, out of interest, what happens at the other end(s) of the 'continuous vent' marked on the detail? To explain, while it appears that you may not have the 'in', do you have the 'out' at the top? The pic does not go high enough for us to see.

... or is it just out of sight? There appears to be a slight 'shadow', which might be a flashing, but the camera angle is not quite right to see. Is your architect engaged to draw and specify only, or to have a supervisory role? If the latter then the arch't should be able to tell you what has been built and what should have been built. How was the contractor engaged? If it was effectively 'build this (house) according to these (plans)' then you can reasonably argue that they haven't.

I may have misread the dwg. It seems like, as drawn, there's a ventilated void, meaning that the render must be on a renderboard on battens. If a typical renderboard is no more than 15mm thick (and often less) then there's precious little to grind into. Or was the detail changed and the EWI was rendered directly onto the insulant, in which case it is not built as drawn and cannot function (in a 'vented fashion') as intended. Or have I read it all wrong? Is the answer to the mystery in 'E.W.3'?

How thin is thin? My 'go-to overlay' used to be 25mm PIR and T&G OSB floating (not fixed) on top, but I always used 18mm. 9mm might just be OK (I don't know - I have never tried, and of course you don't get the T&G) but I think 6mm over PIR might feel a bit like walking on a blancmange.