Redbeard

Sorry, I've been trying to find 'Fred Drift''s comment. @ProDave, are you using voice activated posting?! Sorry again!

Doesn't sound right to me, but try the manuf'r. Importantly, AFAIK, it is not a vapor control layer. It is a waterproof membrane which is capable of 'breathing' *out*.

Much as I like to advise getting the heat-loss down as low as possible before considering a HP it is not true that they won't work in a poorly-insulated property, but they may cost a fortune to run, or simply even not be big enough (most single-phase HPs max out at 16kW). Depends a lot on the size of your house. Depending on the current flow temp of your boiler (some old houses run at 60 - 70C) you may need to increase the size of some or all rads. There are high-temp HPs but I am not at all sure of the CoPs (Co-efficient of performance - kWh of heat out for each kWh of elec to run the HP) they offer. You are right also that an over-sized pump (as you improve the fabric performance) could be an issue, though others will know more than I do about HP modulation - effectively the ability to 'behave' like a smaller 'boiler' and not shorten its own life by short-cycling a lot. A buffer tank may be recommended too I am not sure that unless you either have a **huge** array of solar and batteries or need a lot of heat in the summer. By all means note that if you have a HP a sunny day may offer a little bit of help to it, but I would not be expecting much. Lots of advice on here already re internal insulation and what is best for old stone buildings. Does your house have a high degree of exposure?

Assume min 60 yr life required, so not corrugated bitumen board, in my experience (although poorly-supported bitumen boards 'go' a lot quicker). I took off some (?pre WW2?) corrugated in about 2015 and yes, it was 'chewy' at the edges, but (a) so much thicker than modern, (b) still with most of its galvanising on and (c) solid as a rock at all but the edges. Self-coloured, of course. Epoxy if you can. Layers I could guess, but I'd be guessing, so I will leave that to others. Battens and counter-battens will be involved, I suspect.

What you need to stop is the tamped under-layer 'extruding' out and causing the paving to drop. I don't think loose anything will help that much. What I had in mind was to cut away small areas at a time of the cut-down haunching and back-fill with concrete to the 'point of the triangle', with that infill going below the level of the tamped under-layer to form a 'footing'. Then run a sloped area of concrete from the same level as the 'footing' up to the bottom of the cut-down haunching. If I have misunderstood, and there is something solid holding up the under-layer which I think I can see exposed (and thus unsupported) , please correct me.

Get a structural engineer to do sketches and calcs. BCO always took SE's calcs as 'Gospel' in my experience.

Hello. I suspect you need to excavate so that the haunching has a footing, then at very least make sure your new, lower haunching physically connects with the existing 'mini-haunch'. I think I would under-cut the 'mini-haunch' slightly.

Agreed, to some extent, but the aim is to eliminate unintentional ventilation and replace it with intentional, even if there's a bit of overlap as the 'unintentional' is being designed out. Thanks @JohnMo. I had looked at those, but since they 'will open and close based on humidity...' and the 'air in' will be in one room with the fan 'out' in a wetter room it may depend on how good the inlet units are at their job. In a less-than-ideal situation the humidity could reduce in the 'inlet' room, making the inlet vent close. However the dMEV fan is running permanently (albeit at only 1-2W) and pulling against a closed inlet. As @gravelld suggests, at the 'start of things' the dMEV fan will just pull in air via 'unintentional' routes, but when these are all closed...? I suspect the Glidevale unit may be fine, but any comments on my 'scenario' gratefully received.

dMEV usually functions with a window trickle vent as the 'inlet' part. Some of these are baffled which helps to reduce excessive ('unwanted') ventilation. Due to the window design a window vent is not possible. There simply is not enough 'meat' on the frame. I am trying to source a baffled wall vent to use as the 'in' part of a dMEV installation (probably a Greenwood CV2) but am really reluctant to use a bog-standard air-brick which is not baffled at all. Does anyone have any ideas as to what I might use? Thanks.

Was the installer HETAS registered? If not, who signed off for Bldg Regs? If installer is HETAS reg'd may be worth asking HETAS if they have a minimum standard for making good. ('Not leaking' would be part of it if I wrote one!). Of course HETAS is (I guess) more about combustion safety than roof-work, but they are very closely linked - i.e. part of the same job. I would also get a quote for making good properly and inform the installer that this is what it will cost them.

FENSA is a Self-Assessment body, in the same way as HETAS and certain elec bodies for their areas of expertise. If you don't use FENSA (AFAIK there is not another windows SA scheme) you (or your contractor if you have one) have to apply (and pay) for B Regs approval. I nearly always do that via a Bldg Notice. Around £200 when I last did it. May be more now, and prices vary a bit between authorities anyway. If you do all the installation work yourself be sure you are happy with assuming the Principal Designer and Principal Contractor roles yourself (shouldn't be an issue with windows but may be for more involved work. Still *could* be for complicated window installs, I guess.) Given the passage of time S & F for £850 sounds not so far from my c£735/m2 supply only in 2022 for another high-spec 3G supplier.

Agree with Compacfoam, and definitely at the bottom too. I think we used 75mm. Consider removing some masonry if you have already built up.

It certainly isn't invisible, but I have seen far worse. My worry is that they have apparently chosen to site the joint well on your neighbour's side, so that if (as the neighbour seems to forecast) it does leak, your neighbour 'gets it'. Obviously not a great strategy for good neighbourly relations. Since the scaff has come down you are a little stumped in the short term. Long-term bargaining point could be for the roofer to return, make a tidier job of the joint (to your neighbour's satisfaction in particular) and make the joint on the boundary. Of course we cannot see the main joint behind and on the other elevation.

Unless the son is doing the work entirely financially unrewarded there is an argument that a contract exists. If that is the case then, unless his insurer precludes work for family members, his insurance is probably valid for the work - if he has any. Don't worry much about him being a 'sole trader' as opposed to ltd co. Many, including me, have no wish to be more than a sole trader, and it's a perfectly acceptable business model if you don't feel the need to limit liability.

Possibly XPS-insulated tiling board. Seems to have reinforced (?)GRP on each side, made to take internal plaster, which would therefore happily take render. XPS is used outside in below-ground EWI (whether it needs to be or not - discuss - in another thread!) so no problem in this location. Sorted (?). Even better, just checked for vendor - Jackoboard is one, and they do varying thicknesses. Whooppee! Seems made for your job.

Excellent news and very speedy service.

Gov't Best Practice guide for rooms-in-roofs says 50mm ventilation gap between the insulation and the membrane. I realise yours is not but it sounds like the set-up is similar.

Please do try to keep relevant content on here wherever possible, or summarise if you have an “Eureka!” moment, as solutions gained off air do not benefit the masses 🙏. Gratsi! Yep, did that for just that reason - replied on the open forum. Thanks for the reminder anyway.

It's about thermal by-pass. If you do EWI and somehow cold air gets into the 'sandwich' inside of the EWI you just have a very expensive fat layer of render.

Most on here would suggest filling the residual cavity if there is any suggestion whatsoever that the cavity may be less than 100 per cent free from air ingress. That could be a significant issue. You don't want to have a bunch of expensive insulation hanging on the outside looking pretty (only). NB I have not read all the thread, juts the 1st page or so, so I may have missed relevant stuff. Edit. Tried to send you a message, but 'EinTopaz cannot receive messages'. Do you or the moderators know why?

I want to add Larsen Trusses and 250mm+ of mainly flexi wood-fibre to my Victorian roof. 75mm rafters, 270mm purlins. He wrote me as report stating that given the reductions in weight by removal of exg ceilings etc and the commensurate increase by insulating would result in some net gain. However while he said that such timbers would not be approved in a new-build he is satisfied that it will take all built loads and the worst-case snow load. That will keep BCO happy. It sounds like you already have the 'ammunition' you need.

Sensible reply as promised. I am really sorry you have had this issue. The manufacturer's info does not seem terribly comprehensive, and how does that 'high mortality seal' (what?!) at perimeters only deal with air-tightness? The instructions for bringing cables through the insulation make no mention of the need for air-tightness, or I may have missed it. Also one of the pictures seems to show (OK, may be my old eyes) a gap between sheets wider than I would wish (i.e. bigger than not a gap at all). There is ref to a condensation risk assessment in exposed areas. There should be one in any case but, as per @Iceverge's post, any 'failure' - quite possible at 100mm - might well attract a recommendation for a VCL from Glaser Method calcs. WUFI or similar may have different views. Edit: Like you, OP, I would be worried about the same firm doing the job again. One might argue that the reality of your installation may have shocked them so much that they will never do a job like that again, but an inescapable fact is that someone signed that off as OK. How confident could you be of 'second time lucky? This is hugely disappointing given that it was presumably done under the auspices of PAS 2035, which came out of the Bonfield Review into public funded retrofit after some spectacularly awful failures. Worrying too.

I think the 'high mortality seal' only applies in marine environments. Sorry! Sensible reply later!

I take it you are talking flexi WF? I found a handsaw and, as per @torre, compression, worked well. For rigid WF Pavatex sell a blade for a reciprocating saw but TBH it was not a success for me. Circular saw with dust extraction worked for rigid WF. 2 passes - one from each side - for thicker sheets.

So, we've got (?) sub-75mm rafters and some Recticel. The current gov't standards recommend a 50mm ventilation gap with sufficient vents on each side. What thickness of Recticel did they use? I fear that problems may have been built in under that nice-looking roof. (and of course its failure to run off into gutters is at least one). I agree wholeheartedly with @Nickfromwales. They need to be invited back to tell you how they will make what they have done actually work in practice. (Of course we don't know the specifics of the 'contract'. It would certainly be useful to know, for example, is there was any 'you do this and I'll do that' agreement, which could alter the facts of what we appear to see).