Thorfun

and thank you to all the other suggestions. this forum, once again, proves how awesome it is. 🤘

thanks. will definitely be minimal removal as I will use an 8mm bit which is enough for the foam gun tube to fit up, then I can fill while retracting the tube and it will fill down the gap. now just need to decide whether to use expanding foam or Orcon-F!

I'm sorry but I don't understand the whole removing material from compression area while maintaining tension material bit! I'd have to drill 'upwards' as I can't get a drill in above close to the end of the truss due to the angle of the roof (35°). so are you suggesting to drill at that point I circled in red to only the half way up the cord? that could potentially give me enough to get the nozzle up and then fire away with expanding foam which should, in theory, expand upwards to fill the gap between the cords. then as I pull the nozzle out I keep firing with foam which will fill the gap in the hole I'd just drilled. I can then tape top and bottom between that line of foam and the AVCL and job done! 🙂

very interesting idea. although I guess I couldn't guarantee how airtight that will be so I'd like to use some form of foam/tape/silicone to ensure an airtight barrier. also, would that not make them 'twist' where screwed together when compared to the rest of the truss? and, any potential detrimental effect on the battens and tiles above? but could potentially think about doing both solutions, foam and screws!

that's good to know. don't suppose you'd know if I drill vertically between the two cords taking a couple of mm off each one how that would affect the integrity do you? something like the below: then I could get a nozzle all the way and create a vertical line of foam/silicone/orcon-F and then tape underneath and above and that should seal it all. something like this?

this is an interesting idea and extends @Conor's suggestion. I presume cross drilling is less detrimental to the structural integrity of the trusses than drilling vertically between the 2 and 'taking some off the sides', so to speak? I could also drill alternate holes on each truss to halve the number of holes in a single truss?

now I really want to know what it was! 😂

I do have some Orcon-F but, again, the issue is the gap is too small to get a nozzle up there. also, the joists run the width of the house so I can't just seal top and bottom where the AVCL is as air can get between the joists along the entire length of the double truss.

it's tight to get any sort of nozzle in unless I can find/print a nozzle that's less than 5mm in diameter. drilling is an interesting option but I'd be concerned about taking too much off the roof trusses and it affecting their weight bearing capability. (yes I am paranoid!!). although, I guess a 10mm hole would allow a nozzle to get in there and would only strip a couple of mm off each joist.

yeah, I definitely wish I'd thought of it before as I could've easily sealed from the outside! but at no point when the TF was being erected did it cross my mind that those double trusses would cause a hole in the airtightness layer. foam sheet could be an option I guess. maybe I could get some compriband, or similar, and push that up with a steel ruler? then that would expand to fill the gaps? any other possible products that could do this job?

greetings. we're doing the airtightness at the moment and have come across and interesting/annoying detail around the attic trusses! we have 4 x 'double trusses' where two trusses are joined together. sadly they're not joined very tightly and it's become apparent that they are now a hole through our airtightness layer. 😞 so that gap will go to the outside where the cladding is already installed covering it so I can no longer get to it from the outside. that gap also spans the entire width of the roof so taping underneath and on top, although possible, is not ideal especially as so of the length of the joists are covered with chipboard flooring. I was thinking of 'injecting' expanding foam into that gap to try and fill it as much as possible to reduce the air hole but the extension straw I have is too fat. the gap is about 5mm on this particular joist but others are smaller. any ideas about how best to block this air gap? ps. I do have a 3D printer so could, in theory, print myself a nozzle that's thin enough to fit in the gap but my 3D modelling skills are limited.

we did the few voids on our basement slab with sand to just level it out a bit. there weren't that many though tbh.

I got my natural Spanish slates from Jewson. the Mont Azul Lombeiro. they were around £1.25 a slate Nov 2021. a very good slate and our roofer was very impressed with them. even another BM rep came to site and saw them and said they were really good for that price and Jewson were on to a winner there! might be worth checking them out. according to the owner of the Mont Azul brand they come from the same quarry as the Cupa slates. some pictures in my blog post, it'd be interested to see what the current price is on them as could save you some money.

Or just turn the other APs off! A lot easier than walking around the house with a TV and Firestick. 😉

buy a Nespresso (or other brand coffee maker) and make your own latte for a lot less than £3! 😉

can't you just turn the PV inverter off to do your testing? that way no PV will be generated. just a thought.

our MVHR outlets are 250mm reducing down to 200mm pipework internally. just fyi. but we have a larger house with 90mm semi-rigid ducting so I guess we need to bring in more air.

welcome. I hate to put a downer on this exciting time for you but, and I speak from personal experience, don't spend too much on ideas/designs/architects/site investigations etc until you've exchanged contracts! we spent many thousands on a previous property only to be gazzumped about 1 week before exchange of contracts. money down the drain. best of luck with it all!

when you say 'pro' version are you talking about the 'Industrial' or the 'Trade' versions?

mine was designed by TSD (Tanners Structural Design) and had 90o insulation. in fact, where you have the raised area of hardcore/sand we just used more insulation. here's ours for reference. that above is using the Kore preformed insulation but our groundworkers just bought EPS300/EPS100 without the sloping former and cut it to fit on-site. photo below: hope this helps and it's posted with the caveat that any changes to your foundation/slab design should be ratified by your structural engineer.

still quite large though albeit kind of midway between the 1.67mm and 4mm - 5mm others have. I can guarantee you that I will end up not bothering! it's one of a 1000 things on my list of things to do and think about and it is rather rapidly moving down that list.

If ridge height is a limiting factor can you consider a contemporary building with a flat/shallow mono-pitch roof? Mira not to everyone’s taste but with a good architect/designer on-board it could be a wow factor and also does away with the limited headroom upstairs. just a thought

How are you and who is insulating the roof? If you’re doing it I highly recommend cut rafters! Having almost finished installing 190mm mineral wool between the rafters and cutting PIR to go underneath the rafters I can honestly say I wish I had a cut roof! but, if I was to do it again I’d go for really wide cut rafters ( or I-joists) and find someone to fill with blown cellulose.

yeah. this is a good idea. our groundworkers wouldn't start until things started drying up a bit in April, although they were digging 3.5m down to build a basement!