Redbeard

Expanded metal mesh, galvanised if you have normal-depth pockets or stainless steel if you are rich! I used lime over galvanised expamet 16 years ago and nothing has fallen off!

Good Qs, @Iceverge. @deuce22, you had said: " Merely so my mental picture can be complete, are those boards there? You had referred to this as a warm roof. Strictly it's a hybrid warm roof, as (in my view) it is generally accepted that a Warm Roof has all the insulation above the roof structure. Precautions need to apply where some of the insulation is above the rafters and some between, lest the 'between' insulation should cool the 'interface' (the boards or 'not-boards' referred to above) between itself and the insulation above the rafters. Has an interstitial condensation risk assessment been done on this basis? If a CRA has not been done then a 'rule-of-thumb' from a highly-respected colleague is that two-thirds of the R value should be over the rafters and on-third between. (Reverse that, for example and the interface gets potentially too cool). Taking PIR as 0.022W/mK lambda value the R value of the PIR is 6.81m2K/W. Min wool lambda values vary but if we take a worst-case at 0.044W/mK that gives us an R value of 3.41m2K/W BUT we have rafters 'interrupting, which I am not calculating at this point. With no real justification let's say the 'timber fraction' lowers the R value to 3.0. That about fits the rule of thumb, but there's still the outstanding question-mark - the subject of your thread - vapour control. @Firsttimer I like the dropped ceiling idea. Still needs excellent attention to detail on the VCL above, though - a job for an obsessive! Even the fixings of the dropped ceiling become potentially-leaky penetrations.

How 'very' is 'very'? Have you had a test? You say So is the stuffiness in the bedroom happening even with dMEV running and trickle vent(s?) in that room open?

Wow! Think I'd be fed up too! I regret my patented (not) 'Spotlight condom' does not exist (though I think it should!). However Partel make this: https://www.partel.co.uk/product/airtight-downlight-cover/ which might work (???) (Actually, now I have looked at it I don't think it would work, as it's obviously made to sit down on a ceiling, whereas your lights will, I think, be pushed up into holes in the ceiling). I feel you are going to have to fabricate a version of the 'spotlight Condom' which can be fitted with a/t tape from below and then pushed up with the spotlight.

Not easily, no, if I follow your description correctly. I assume the ceiling is not up yet, although the 'lots of spots.. etc' seems to imply otherwise, since you need a ceiling to fit the spotlights in. If the ceiling is not in you could *hope* to achieve vapour-tightness IF you can get vapour-tight shrouds for every 'intrusion'. This will effectively be a 'spotlight condom' with a grommet to fir tightly over the cable. And remember that if you pull an EPDM grommet over more than one cable it will not be air- or vapour-tight. 2 wires, 2 grommets. I hope you can make it work.

I got confused re this, but assume that in this sentence 'cork' should actually be 'core'??

This is UW (while unit U value - good, as it includes everything) not Ug (centre-pane U value - less good, for obvious reasons), is it? I have some scepticism re alu windows and doors but they are undoubtedly a lot better than the old 1970's and 1980's non-thermally-broken ones. I was pretty surprised to see how 'vestigial' the 'thermal break' was on one set of alu windows but (after a bit of a shock when the new-build was still pretty 'moist' and the windows were pouring with condensation) they seemed to 'settle down'.

...with the mansard section, do you mean? Is the lead new, or is that what was there before. If the latter then I doubt the new roofers have got it wrong, and if the lead is new I would imagine they would simply have replicated what was there before. No obvious reason to worry, I should have thought, but that's from an assumption that it's a fair roofer, not from anything the pics show (or don't).

Urghhh! If the only problem they have left you with is a scrappy sticky-out membrane then it is arguably just an aesthetic consideration, but it does make you wonder whether they have done anything else 'non-standard'. At least there is an iron on the end of the hip.

Sorry to hear of your problems. How about phoning or writing to RIBA (Royal Institute of British Architects) and ARB (Architects' Registration Board), explaining the paternity leave matter and ask them if that is normal behaviour. What explanation was given to you for the charge? Presumably that hours were taken in effecting the transfer of work, but if your contract is for provision of a service then it should not matter who does it, and if they have to faff around behind the scenes because of personnel issues that should surely not be a problem you should have to *pay*' for...?

Are you expecting it to pick up much water? (Does the path fall towards it, for example?). I have incorporated a perforated pipe, with the gravel over it, (and a drain connection at the end) at the base of my EWI.

It is hard to come up with possible answers without fully understanding the construction, but I'll make a guess that the top of the offshot gable/boundary wall (where you need the gutter particularly) is 'capped' with the metal detail, with a 'downstand' down the wall as shown and, presumably, and 'upstand' behind the vertical sheeting. I would be asking myself 'how easily could the vertical sheeting come off so that the 'downstand/upstand detail' I described (however badly!) could be replaced by an 'upstand/upstand' detail, basically a wide gutter, which sits on top of the wall where the existing detail sits?'. So you said: I think that if what you describe as the 'ledge' is what I describe as the 'upstand/downstand detail' then it's not about sitting a gutter on top - it's about replacing one with the other. In terms of liability how tight were the stipulations in the design/contract? Was it 'positive performance-led', insofar as 'it must do this and that'? Were there any negatives - 'It must not do that', for example where 'that' may be tipping water down your wall and onto the heads of the neighbours. And who designed the 'metal top'? Contractor's designer or your architect? Somehow the issue of liability needs to be raised with all parties. Plainly what you have (though it looks quite nice!) is not performing properly. I quite understand your neighbours not wanting to agree to an 'aerial trespass' (no, I am sure that does not exist in so many words, but I hope you know what I mean)

Hello. Your penultimate pic appears to be an earlier one with a red line added, but no apparent explanation of the red line. Is it meant to say 'should this have been a gutter with a fall-pipe at the RH end?'. In which case 'yes. You seem to refer to this wall as the 'party wall'. I can see it appears to be the boundary, but then (single-storey, I assume) bldg at the bottom appears to be a garage. Does it share that wall? Seems to me there ought to be gutters at the bottom of the metal cladding all round. I cannot read the pics too well but it looks at if the builder has assumed that if it's in line it's all one wall and does not need a gutter. I think the different behaviour of the 2 materials - one completely impervious with no 'buffering' and one (the brickwork) somewhat absorbent and thus 'buffering' - means a gutter is necessary. I cannot see enough to know that this would solve all your problems.

Thanks @Ferdinand, that makes sense!

Hi Lewis, It would certainly help me greatly (and probably others too) if you defined the types of social relation(s?) you mean, rather than having to open the file to find out. Is that possible? (By the way, I have just received a request to take part in another survey and I cannot read the pro forma to see if it's for me or not, since I cannot get past each page without filling it in! If yours is like this it may put people off starting. Hopefully it's not!)

What about pre-fabricated straw panels? "If you’d like to get in touch with Barbara about consultancy, EcoCocon’s prefabricated panels, or anything else, you can email her at barbara@strawbuilding.org.uk or contact her by phone on 07720 716 589."

Cork board, perhaps? Or perhaps not is low cost is a criterion.

I may be wrong but I am sure I have wrung water out of Rockwool like out of a sponge, so I am not sure it is water-resistant. Is it not that the rigid or semi-rigid 'batts' may have a water-repellent coating?

You don't go on to say that *you* have a party wall agreement for your works. Have you? Whatever the current situation you need PW advice. I don't know how it complicates matters if you have to invoke the PW Act after you have started but for reasons stated by others above you need to, I think.

OK: 150 PIR on the sloping ceilings would meet the Regs. 60 WF on the walls wouldn't, but you can put a cogent argument that you are reducing interstitial condensation risks and thus potentially extending the life of the building at a slight 'energy cost'. If I understand you correctly I think you are saying that if you cannot comply to the letter you may be better saving the BC costs and doing the best you can. I think the issue may arise when you come to sell, when the buyer's solicitor asks re works and re BC approval. If there is none they throw up their hands in horror but ultimately agree to be a lot less horrified if you drop the price, probably by an amount far in excess of the BC fee. Yes I know about indemnity policies and so on, but (a) that they cost and (b) that you cannot apparently get one if BC are already aware of the breach, which they may be via the potential purchaser's enquiries. I hope this helps. I don't expect everyone to agree with me but, in old examiner-speak it at least 'shows my workings'.

But you want a vapour control layer (VCL) on the warm side of the insulation, so where you say 'Breathable membrane flat on top of the OSB' wants to be a VCL, not a breathable membrane, in my view.

Yes. I can't help feeling that clarity would have been helped if they had used something like 'Lead Designer (BSA)' and 'Lead Contractor (BSA)' (no, not the Birmingham Small Arms BSA!) to avoid confusion between BSA/B Regs and CDM.

Internal insulation (IWI) carries the biggest risk of interstitial condensation - vapour condensing on the masonry surface of the wall behind the insulation, since the insulation make the wall cold by isolating it from the heat source. It may be a good compromise solution for existing buildings but not new-build, in my view. How about building solid block with EWI (thickness depending on material)? Why are you thinking of a cavity. What is it doing, in your view?

Tell us more about that. Where is it on the pics from outside? In general the tiles don't look too bad, although the bottom row LHS looks a little 'unhappy'.

Welcome! Frankly I'd have done nothing. 'Underfelt' (or, now, 'breather membrane') is a nice-to-have belt-and-braces luxury. My 130-year-old roof has no membrane. As long as the slates or tiles are in good order I would argue that you need do nothing. The membrane is there to catch the water if the tiles or slates fall off. Arguably, no slates falling off, less need for membrane. If the felt is crumbly it would, I suspect, be worth getting an asbestos test done since, if I remember correctly, some felts at some time were reinforced with asbestos fibres (hse.gov.uk's asbestos essentials section will tell if my memory is wrong). A bit more detail will allow us to give a more informed opinion. With the exception of the asbestos issue referred to above, no need to worry much (if at all) unless the external pics you haven't shown us yet show areas of slipped or damaged slates/tiles.