crispy_wafer

You've pretty much just described my install... 1ph to crappy bungalow, 1ph to new build, 1ph unused, but it will be a big garage with living space above. I guess it comes down to metering and the properties are they staying in your name, or are you looking to sell one?

I bought a few of them steel rectangular, slot together jobbies of FB marketplace, not suitable in anyway shape or form for trade use, but for DIY use and hedge trimming up to about 2.5m platform height they are perfick! £200 or thereabouts Easily create a platform long enough for a 3.9m board to span. If you want to go any higher than that forget it get a proper one like those above!

Polypipe, hit your local civils place, often worth their weight in gold through experience and advice.

did you try or think about what @Nickfromwales suggested eps at the bottom of the cavity, xps board against the outer leaf to insulate against the cold bridges then fill with concrete.

use a 135 junction and shove a 45 in the end of it.

I did similar, kept accessible, because I’ve put stop taps on the two feeds off the main. Saves me having to go out to the road to kill the individual tails. I’m in the process(2 years, because not important just yet) of building up a chamber, it’ll be something along the lines of 700*1250 ish so I can get into it should I ever need to. There’s probably a better way, maybe theres a manifold for mdpe which could simplify matters, haven’t looked tbh.

Just be mindful, I wasnt... With trusses you may get cross bracing included! makes insulating a pain in bottom as the bracing can get in the way, it can be done though, just takes a little more time.

I’d say that he’s right to concerned that screw/nail holes can be affected by rain/moisture, no different to the board joints really, so put a small dob of d4 over the nail/screw will help. A floor scraper when watertight to lift the foam.

AICO, should cover most, if not all needs

I cant add too much, but in the first instance i'd ask, does the HP have a pump built in, if it does, then does it have enough grunt to supply the needed litres per minute for the install.

Personally, under the slab I wouldnt run copper, i guess many have done in the past though, Me, I'd run a 110mm soil pipe and push 25mm mdpe through it, rest bend where it comes back out of the slab. No pipe joints where you cant get to them.

Nice idea, yeah I'd run it past your SE for peace of mind, or even @Gus Potter might lend an ear for his thoughts. I cant help too much, because I've gone with central spine, however when time comes for manufacture, assuming you don't fabricate it yourself, don't be afraid to look up local fabrication firms and joiners for treads.

downpipe at one end or in the middle of the run?

🤣 appreciate the last couple of posts, I've been eyeing up steel baths too...

Would it be easier to just batten with 3*1 or 4*1, using the lowest spot as your zero point, and shim out the battens at the high spots.