Redbeard

It's a tiny point, but that's arguably what the sand blinding is for. I guess no harm having belt and braces!

Out of interest, why 30mm EPS below the DPM?

Where or what is your Vapour Control Layer? The only thing I can see in the right place is If that's a VCL is it taped to within an inch of its life at all joints, penetrations and perimeters?

Is this new-ish render or old? Looks like modern thin-coat, in which case I am surprised it's a metal bead, not plastic. The rust will probably come back eventually, whatever barrier paint you use, and trying to paint over it in render colour may leave the bead exposed. Why not dig out the angle bead and buy a plastic bead and a bag of base-coat render, and then cast around on here for someone with a part-tub of 'gritty top-coat' left. If the colour is not a perfect match you can get some masonry paint to go over.

I imagine the is armoured in some way, and not a PVC-sheathed cable. Just in case any PVC-sheathed cables are involved, remember (a) that polystyrene (expanded or extruded) leaches the plasticisers out of PVC cable sheathing (symptoms include PS insulation 'glued' to the cable) and (b) that cables (particularly 'grunty' cables, whatever they are sheathed in) are not meant to be 'tucked up warm' in insulation.

Even when I have been doing stuff on a Building Notice I have had to provide SE calcs for lintels, footing pits etc. Likewise they can require wired linked smoke alarms (which in my particular case have been a PITA) and will ask you to answer requests for fire rating details. I have found, since the 2022 regs, that some BCOs are not 100% sure what they need to be asking for. I was asked re surface spread of flame for rigid wood-fibre-board with 8-10mm plaster on. I Q'd it and they withdrew that request, acknowledging that the board was completely covered, with approx 30 min fire resistance in the plaster. I agree wholeheartedly, though, that checking is important. I used to get a bit fed up when BCOs did *not* check and ask Qs re my work.

Good to hear that. Sadly the company I used to use had a 'no foreign sales' policy as soon as we left the EU. If you bought abroad who did you use, if I may ask?

All the other bits seem feasible provided that they make their peace as required (for example a build-over agreement with the WA), but no Building Notice? Have they started on site yet? They don't have to submit it in advance. Soakaway is allowable if they have permission to discharge to the main drain. I was expecting to get refused permission as it's a combined sewer but my WA seemed quite happy. Nevertheless since it appears that the neighbour may not be as 'sharing' as you would wish, I sympathise and hope that it is not too stressful.

My ext'n was post-and-beam, EWI'd with 160mm rigid wood-fibre, and a further 100 (or maybe 80 - can't remember) between posts. Thus the majority of the insulation outboard of the structure. Could you do that?

I had some clients pay the window installer to tape. Much of it needed re-doing. It appeared that the fitters in that case did not have a full understanding of the (taping) job. It has been made more difficult by EU-exit, but I used to save a lot buying tape from Germany.

Off-topic, but out of interest, is the v shallow roof pitch as a result of using PD rules? ... or is there a window in the main elev just above ext'n ridge height?

What is the relationship like with the neighbour and/or the neighbour's contractor? I would set out very clearly what you would like any protection to achieve, and ask them to make a proposal for your agreement. Make it clear in writing that if the arrangements they make are deficient in any way, and your property is damaged in any way, your course of action will be (xxx). If this is all done in advance, in writing they cannot say later that they were not warned. (I fully accept that if there is less than 100% co-operation this is a lot easier to say than to achieve).

I would probably not be remotely bothered about the chimney - there's not much of it and you might not keep it anyway. But 'nothing wrong...'.?.. till it droops?

Note there is a difference between an RICS 'Full Structural Survey' (or whatever it is now called - I cannot remember) and a Structural Engineer's Report. The latter will, if you so instruct, report simply on the issue in question.

Is this a single-storey property, or 2-storey? Can you post some general pics of that elevation externally? Those bricks look weirdly long, unless the internal pic is somehow distorted.

How about: Take the gutter off, fix notched uprights to the existing uprights, the notches allowing them to protrude up above roof level, and fix a horizontal bearer across. This stops your scaff planks falling off the roof. In fact if you take some timbers from there up the line of the roof to where you want to stand, you can them use those timbers to hold your 'stand-on' timbers. I take your point re installing 'cross-noggins', but are you not still standing on the polycarb even with those underneath, with point-loads of feet, instead of spread loads in my 'model'? See my suggestions above.

I'd go with your gut feeling, then, and go for LA.

No, but my general experience of LA vs private BC has been that LABC are more thorough, though to be fair, see-very-little 'fly-bys' can be common to both, and the use of photographic evidence is, in my view, at very least a mixed 'blessing'.

If the flashing remains intact then it seems to me the top (although not where it should be) will not leak. Do you think I am correct in this? If so... cut pieces of 45x45 PSE to fit in each 'bay', fixed to the ledger-plate at the top to prevent 'droop', then make 'tingles' (glorified 'slate straps') to hold the bottom of thhe sheets to stop them falling further. So, 'downstand' down the face of the wall-plate, horizontally across the wall-plate towards the lower end of the poly sheets, then an upstand holding the sheet in place, with a drip-end on it (a little - 15mm? - 'turn-down). Or maybe I haven't read the OP well enough... Yes, I hadn't read the OP well enough!! I see the flashing tape is damaged. Scaffold planks across the lot to support you and spread the (otherwise) 'point-loads'. I would suggest do this *after* you have put the restraint straps on the bottom. Then repair the flashing. (Assuming it is 'flashband' perhaps take the opportunity to do in lead - don't forget the patination oil. Unless you feel you have to I don't think there is any need to hammer the sheets back up as you suggest. I think my 'remedials' suggestion sorts that.

I suspect the more important Q is how far down will his wall start? If it is genuinely 3m tall it will have to start in a trench probably 900 (all right, maybe only 600, but I am Not A Structural Engineer) deeper even than that. If he does not start below the level of your land then, as far as I can see, it may be able to behave like a snowplough over the years, slowly moving his garden towards yours! But I may be wrong!...

I have had many more problems with nuisance tripping with my 3 linked mains-fed alarms than with any battery alarm over 30+ years. I now use the 10-year sealed ones. Mains-fed was a stipulation of BCO but they did not have to live with the jolly things going off at random times. We have not-linked but functional alarms in the relevant areas which do not nuisance-trip.

That's incredibly well camouflaged!

I wondered if maybe you'd got too much caulk. That won't rough up without looking like it's been attacked by a magpie. I cannot explain why the top and sides peeled. You mention plasterboard. Was it joint-filled and then paint straight on the plasterboard? That should adhere OK, but if it was skimmed it could have been over -'polished' - again, potential poor adhesion. Come to think of it, if it is just joint-filled, that may account for your top and sides if the joint filler was over-trowelled. Have to say I have never had adhesion probs on tape and fill pl'bd. I have no idea bout the colours of masking tape I'm afraid - all a bit hi-tech for me! It was (and is) all buff for me!

It looks like just inadequate adhesion/'keying' of the pink paint to the white under-layer (what is it?). Can I guess that you have maybe run the skirting paint (a top-coat) onto the wall? If this is the case then it's your reason; gloss (or satin or whatever) is a top coat and not designed to 'hold' another coat on top. Fine sandpaper, rough it up, preferably use an undercoat, then gloss/satin on top. (Alternatively I may have misunderstood the issue, in which case please tell me where I have 'mis-assumed' and correct me).

+1 to @Iceverge's a/t tape. Unless there is a solid layer behind the membrane I do not see how a squirt of sealant can be relied on to actually seal the hole. (And, come to think about it, if there is a solid layer you can't get to the hole itself anyway (to tape or to 'squirt' - You'd just have to squirt sealant down the batten-hole and hope. All a bit 'loose', perhaps.