G and J

I didn’t realise that was an option. Rolly and I manually erected our frame so that would have stressed the PIR fill so wouldn’t have worked for us anyway but for normal builds where a crane is used I can see that addressing all the in-frame PIR fitting issues.

Grey silicone on white sanitary ware would irritate me more than white silicone on grey tiles. Done well the white silicone could look like part of the shower tray and almost disappear from one’s notice. But don’t do aesthetics, J does. One has to recognise one’s pay grade lol

Is that because they are specifying it but not installing it? In a calculation, PIR makes a wall build up seem great from a thickness/u value perspective. So at the point of buying a timber frame it helps the sale. We took the view that a few inches off room sizes was an ok price to pay for a nicer ‘sounding’ house with still reasonable wall insulation. Your architect may be different, but most (it appears to me) never build stuff. Shredded paper looks good on websites, but one lesson from our build is that doing non standard stuff is like pushing a pebble uphill with your nose. Fighting that one through for airtightness was worth it. Given the properties of mineral wool which is widely available and understood I would struggle to build a case for cellulose. But it’s a good talking point over canapés I guess. I really must find out what a canapé is lol

Sorry, forgot to post this. Exhibit A : one wrinkly membrane…

Fairs fair though, you are building a 3 underground storey defcon 1 bunker system. At least I assume you are at those lengths. And wow, our whole house isn’t as tall as your smallest pile.

I (G) did hours and hours of working through options for wall build ups. Drove J, the architect and a lot of buildhub dudes mad with my endless ‘what ifs’. In the end the conclusion surprised me. Getting the most wall insulation is not paramount. Adding insulation underfloor and in the loft is easy. Improving airtightness (don’t get me started) is massively more important than absolute wall u value. Glazing further undermines the benefit of excessive wall insulation. So then decrement delay (ask a nearby grown up to explain that one) and sound attenuation become the driving factor. Had I known what a bugger PIR is to work with I’d have factored that in too, but I didn’t back then. Frame batts (not roll as it falls out) is nicer to work with too. Just don’t push too much in. And don’t ask me why unless you’re wearing ear defenders lol

Absolutely this drove us, (we had a previous room in roof (done by others) and the result was not great) and then we found it really easy to work with. Used the frame therm batts as others have described.

That’s true. When I laid the 120mm layer of polystyrene for our floor it snuck together beautifully tight and flat. The polystyrene has some spring in it so it could be cut to an interference fit and shoe horned in, lovely. The PIR in the other hand, was a bitch. Really nasty dust in the cutting, and however hard I tried still tiny gaps between the boards and to add insult to injury it sat there showing off how different thickness each board was. PIR. Just say NO! lol

Ummm, the title confused me. At first I thought you were talking about insulation outboard of the frame/OSB. But I think you are looking at insulation between the studs of the frame and inboard of that. I think the 120mm PIR in a 140mm stud is about an air gap next to a reflective coating. So better insulation overall than full fill PIR. I am biased. I hate PIR with a passion. Used it under our floor a bit and regretted it. Should’ve made sure I had enough space for polystyrene only. We used mineral wool in our frame and another layer inside. I may be kidding myself but I now believe it’s a nicer job to do and nicer to live in. The only place PIR looks good is on a spreadsheet.

I don’t hold with the ‘do everything yourself or it’s not a self build’ concept. That house wouldn’t be there without you and yours. You’ve shaped it and made it happen. Feel good inside and try and remember not to bore your friends and family too much lol (I, G, fail royally on the last part!)

Moved out of rental, moved into new pad. Lots done but fair bit still to do. Even had a week away in our neglected campervan. Back to work next week, worktops being fitted and we will actually move into our bedroom with any luck. No fancoils yet though, so I’m running even more dark pink than normal.

Thank you Redbeard. My thinking is that if there isn’t a downside to simply adding another layer them why not do that. Reduces probability of leaks perhaps. But logic doesn’t always work with building…

If you can afford it (time, not just £) is it worth talking to him? He maybe bored already and prepared to take on a job that offers flexibility. Our carpenter (recommended by previous trade) is retired and has worked an average of 3 days a week (5 when deadline has required) 1 day a week, when suited etc.

Well, we are back from our week away so it’s back to life, back to reality … And the first question I ponder is what to do about the breather membrane on the front of our house. For various reasons the front upstairs gable of our house has not had its timber outer skin put on. Scaffolding has now gone up so that will be remedied soonish. But what to do about the breather membrane? It’s the expensive Tyvek reflective stuff supplied by ETE, the timber frame company. It’s specc’d for four months exposed. We’ve been a lot more than that. It was put up in September. It now looks a bit like my skin, rather more wrinkly than I’d like. The timber skin is 24mm larch which overlaps nicely so should keep the vast majority of the rain, etc. out. I think the main functions of the membrane are to keep wet out of the frame, and to allow water vapour out so that any atmospheric moisture in the timber of the frame can escape. So do I leave the existing membrane in place and add another layer or is that likely to reduce the passage of moisture too much? Or do I cut the existing stuff away and put new straight onto the OSB of the panels? Guidance gratefully received, as always.

This might not work, but my recollection is that you found a groundworker in the end that you were happy with and who could work with you......could they recommend someone to you.....I ask this because being on "on site self builder" who has a strong vested interest in outcomes is not a situation that everyone is comfortable with (maybe they should be but that's another debate) so having another trade saying "look they're ok, pay on time etc etc" may help your case? This is how we have had good referrals