What research did you do? I am genuinely interested now, I know my earlier post may have come across flippant. I actually edited it down, after writing a fair bit.
Applied to building control who sent information through, had several quotes off builders and what they would do and supply, so basically copied that, internet has vast amounts of information also, that’s why it took so long, there’s so much crap on there. Creating a cavity, vapour barriers, using the correct insulation. One of the biggest things I had to overcome was cross ventilation in the roof due to it been a cold roof rather than the preferred warm and the way the beams ran. I had to create a dropped ceiling allowing a minimum of 50mm air gap front to back, this could only happen once I’d installed under soffit vents when I had new house roof installed (garage is flat rubber roof). When I talked to the building inspector I picked his brains about this via emails and a visit so that was ok and explained what I intended to do with the rest of the garage, they are the experts and agreed I would be fine doing what I did. That’s why when I consulted them on insulation required for U values they advised one thing then the next inspector changed it! The room is only 4m by 2.5m but you’d think I was building a new housing estate.
In regard vapour barriers I had considered thus but was told PIR for what I was doing would be sufficient, that in itself brings conundrums as if you put sockets or spots in the walls ceiling you compromise the insulation bring U value down and possible thermal bridging problems, so I had to change to on surface spotlights and on surface sockets, not ideal but needs must. Also using foil backed insulation to give me a better vapour barrier as the heat rises i5 shouldn’t penetrate through and the air gap above which is about 300mm including the joist space.
Look on YouTube for Steve the roofer and he shows the how bad building regs are in relation to doing stuff now it’s a nightmare, like I said before they now want the PIR taping all the way round, that tape isn’t cheap and it’s time consuming, most builders would do it but I did where needed. The floor was se 200mm below the house so self leveled it, DPM layed , 75mm polystyrene and the 100mm PIR plus 22mm water resistant T&G.
Only time will tell if it’s all ok, my dehumidifier seems to be working well so hopefully by the end of the week the sparky does the second fix and I’ll be good to go to get it all signed off.
What amazes me is the new build I got in 2007 has all sorts of problems you should’ve seen how the insulation was installed in that! God knows who signs them off but it was a joke and the NHBC guarantee isnt worth the paper it’s written on, last time I tried to get help with them it was a minimum £1200 claim or you did it yourself because they had that many issues they just couldn’t afford it u less your roof is falling off.
