Redbeard

Contrary to what the Building Regs would have you believe (DPC should be min 150 above ext gr level) rain in some parts of the country easily bounces up 300mm, particularly off hard surfaces. If I am 'reading' correctly 300mm is about the level of that waste pipe. I had taken the internal floor level to be below that, but is it? Or is it way up by the stepped-out roughcast?

Looks too hard and too moist. If the crack is the dpc, I would hack off the render just above that level, and also look at 'softening' the horizontal surface. I take your point: ...but somehow you need to try to achieve some 'softening'.

London (yellow) brick? Possibly the right sort of area. I could not 'aesthetic' my way out of a paper bag but that on the lower elevs with something darker above seems nice-ish. I'd be worried about white brick.

I have not had a comprehensive read, so apologies if I am countering anything you have already said, but I assume your roof is finished, with tiles/slates/whatever already on. If not, can you increase the depth of rigid WF? As per others' comments it looks like, strictly, your roof is 'the wrong way round', in that, crudely, the 'conventional wisdom' is that you have more above the rafters than between (66.6%/33.4% is sometimes suggested). However I have seen some details (sorry, cannot remember where, but I have a feeling a colleague did this) using WF sarking and fulll-fill Warmcel (recycled newspaper) in deep I-beams, so clearly some people have different ideas. If you decide to 'go for it', why not just put counter-battens on under the rafters to achieve the depth you need, so you do rafter depth in one direction and between counter-battens in the other, which has the virtue of each layer covering the last layer's gaps?

Welcome. What are we looking at? Just the single-storey side bit, or is the front 'projection' part of the proposed ext'n?

I may be misunderstanding this, but I take it this is 1 storey only. What is your absolute limit on internal ceiling ('roof') height? If you build it as you suggest but with a mezzanine sleeping platform could that make it more workable for year+? How are you proposing to build it?

If that's the case the question then is 'where do you run the cables now?' I don't know what sort of house you have, but is a service void feasible? If it is, and you get the spark to pull all the cables, you'll still have to seal all the holes in the membrane, but you can then run all the cables *inside* the a/t layer, except those few which have to breach it, and you now know how to do even that with fewest risks.

Yes, my suggestion of 'grommets-with-a-slit' was effectively to give a substrate to work off, similar (but not as strong as) @Iceverge's ply. Each 'cut grommet-hole' would still require Tescon tape or butyl tape to complete the job.

My thoughts entirely. I am assuming the wiring is pretty well done and that it is far too late to disconnect cables and run them thro' grommets as should have been done. Therefore, as per @Iceverge's mantra above, separate out those bunches, get some OSB/ply behind if you can (as it's a darn sight easier to stick to something which doesn't move away from you!) and do the 'split grommet'/tape idea which I described above. *for each separate cable*. I have never used Pro Clima's butyl but still have some Pavatex butyl tape I use when necessary. It takes bends better than standard a/t tape, though Tescon ('cloth') tape is pretty forgiving. It is very tedious but do not despair. By the time you have 50% of those holes done it will feel like it's all downhill (in a positive way!) from there. And +1 to the DIY 'blower door' idea. That's on my list of things to make too. Best of luck.

You can make your own. I would not like to guarantee they would be quite as good as the proprietary ones, but I have had some success. Basically EPDM, as many holes as you need, and air-tightness tape around the perimeter.

Oh dear! You are not alone, though. Ideally the spark would have used purpose-made cable grommets. Would you have room to separate the cables and cut a square out of the membrane? Get a piece of EPDM (rubber roofing) bigger all round than the square you have cut out and drill holes a good distance apart for the number of cables you have, each hole slightly undersized for the cable. Then make a cut from each hole to the edges of the EPDM square and tuck the cables in. Then get short lengths of air-tightness tape and tape round each cable to the membrane. Finally, use air-tightness tape to tape the EPDM square into the hole in the membrane.

I may be misunderstanding the pics but pics 1 and 4 seem to indicate some 'local issues' more than just the beads. If it were me I would perhaps be allowing in my costings for getting the suspect areas (in particular pic 1 by the door) chopped out and re-rendered as well as the beads. As @nod suggests, use plastic or stainless beads.

Not the same thing at all in terms of aesthetics, but you might have a look at Green Building Company's Stirley Barn project.https://www.greenbuildingstore.co.uk/technical-resource/cre8-barn-stirley-farm-enerphit/

I mean weep-holes to allow water drainage from the retained land behind to reduce pressure on the wall.

It's not quite an answer to your question, but am I right that there are no weep-holes?

I like wood-fibre a lot, and have used it a lot, so it gets my vote. Unless you use the flexi stuff it is heavy, though - 140 - 180kg/m3. You could use an (expensive!) 'Intelligent' VCL like Pro Clima's 'Intello'. Used a lot of that, too. I am not plugging for Pro Clima. I imagine other manuf's make intelligent membranes but I do not know any - yet. Yes - did a quick search. There appear to be others. Search 'intelligent VCL'.

Agree with @ProDave re the vents, and as for the bay I think you ought perhaps to write to the developer explaining that they have effectively 'left your bay in the road' and ask them (with a suggested timescale) to install stout bollards (preferably ones which do not look awful) so that the vehicles hit the bollards instead of your bay. Is that a car-park at the top of the pic? Should trucks be going past your bay?

I would alter the slates/tiles and do the flat roof and cheeks externally, so that the insulation is outboard of the structural frame.

Cannot tell without a picture. Could you post one up, please? Is this a brand-new build?

Without a dwg of the structure it is difficult to be certain whether or not it is required, but if the option is there I would take it. If you are using WF why not screw it to the ply and lime-plaster it? How are the adjacent walls finished? I assume the surrounding walls do not have the finish boards on yet. With plasterboard it's easy: Use a plastic bead and simply skim the pl'bd up to the bead's 'nose' (or 'notional nose' - users of WF may know what I mean) with gypsum then 'all change' for the reveals and plaster in lime with a thin-coat reinforced basecoat and smooth lime finish. The lime plaster (at around 8-10mm) could be your airtightness layer here.

I supervised an EWI job for a client and, because they preferred not to extend the roof-line, we specified an 'EWI gutter', which was/is a double-depth (front-back, not top-bottom) alu gutter which forms a 'roof-ette' to the EWI and projects as far over the new wall surface as the gutter did over the original wall-line. It looks fine but since it is made of 2 lengths I worry about the joint in the long term. The contractor just said 'it's good stuff; it'll last forever' which may be slightly optimistic. I'd have the same worries with your set-up, and more, since 'un-building' the EWI gutter would not involve stripping off some of the roof. I think yours might.

Ok, I see what you mean that it's not damp, but that is not necessarily what the breathability thing is about. If you were using a modern non-breathable insulant which effectively closes off the breathability on the inside, you would want a breathability path to the outside so that if any water vapour *does* get through (via a faulty vapour control layer, for example), it can find a way out to the outside. Get it modelled in WUFI. I am not advertising them but a wood-fibre supply firm with a name rather like how you'd describe your position if you were sitting against a mud bank will do a WUFI assessment for you for free. Basically if you are assured that the insulant (wood-fibre or cork) is OK to let the wall breathe to inside then it may not be so critical if the exterior is less breathable. Better to have a moisture model tell you that than me, though.

I was searching back in Feb for a company which would supply windows using the 'standard' REHAU section, but with a 44mm unit. I had been in touch with REHAU a year and more ago and they sent me a sample of the small bead required to accommodate the 44mm unit. However I could find no supplier in my neck of the woods who would sell me the frames with a 44mm 3G unit. They would do a 36mm unit, but *would not* do 44mm. I have now found a firm in Worcestershire who will supply with a 44mm unit. They said they did not usually do more than 36, but were happy to do so. I know nothing of them but the bloke I spoke to was v helpful. They will apparently ship nationwide.

I agree with this, though how 'lead-free' the water is depends to some extent on mineral deposition within the pipe and how much disturbance there has been. If, for example, a lead pipe with limestone deposits in springs a leak it may well be scraped out to form a 'bell' for a sweated joint, leaving the water in contact with lead as it has not been (given the 'stone lining') for years up to then. It should not be your problem but I am sure you could get one of the companies which tests bore-hole water quality to test a sample from your taps. It won't be free but in the absence of action from SW it may be pragmatic.

Wood-fibre or cork on a lime 'parge-coat' (air-tightness layer) or a cork-enhanced plaster such as Diathonite. I do not think you can be certain that the external render and dash is breathable so I would suggest that you try to get the house modelled in a dynamic condensation risk assessment model such as WUFI which should give you a better idea of the 'safety' of your proposals. I am a great fan of wood-fibre and have used it a great deal. I have not used Diathonite but see some of Green Building Store's Retrofit case studies for details.