goodbyegti

I've got about 35m of a1f in Bristol if interested. I used it on my parapet. You can have it for free. Maybe a little donation to Buildhub?

That's a great link Spinny. A must read for anyone building a flat roof.

For the thermal break you can use a marmox thermoblock or similar and then carry on upwards with the blocks when above the roof PIR. You can attach OSB to the blocks for the GRP.

Thanks! It's 125mm cropped Purbeck limestone and a bit of blue lias. Up against some Surecav except the end which is solid.

We used lime NHL 3 (otterbein), 1 part to 2 parts yellow sand and 1 part grit. It still looks great after a couple of years. It was hard getting a regular bricky to mix it properly. Luckily we found some good masons. You also have to beat it back at just the right time to pack it into the joint. I'd do it again!

^ this, if planning allows!

That is my understanding of it at least. Perhaps one to agree with building control in advance - you could afterall fit a 200mm packer on the final flight to be removed after sign off. Another random thought: could you add a separate 700mm step on to the 700mm landing? Then it becomes a separate flight. It's tough to visualise with no diagram.

That's correct. You can bond a single ply membrane directly to it. The top layer isn't particularly tough, it's very thin, perhaps 1mm?

I lined it up perfectly in the end..BCO have signed off. Just need to plaster!

The family have gone away for half term, so I decided to move the stairs. I need to extend the joists attached to the trimmer, so that they can be hung off the wall. The trimmer won't be supported at both ends, so I think it has to go. Or I need to seriously beef up the joist it's hung off. So I was wondering if anyone has used splice plates to extend joists? I would be adding them right in the middle, near where the sparky has routed all the cables. The original plan was to replace each entire joist with a full length one, but you guessed it, I need to cut literally every service including almost every wire to the consumer unit if I do that. Perhaps I should get on with it?

Some ideas: - Get rid of OSB between joists and firring strips. As above, you can screw the firings at right angles directly into the joists. - Put the VCL on the top side under the PIR. It's much easier to do a good job. Something like Alutrix will immediately give you a waterproof covering. I think there is a rule of thumb that you can then put 1/3rd of the top deck insulation below the VCL. You could use 100mm sheepswool/rockwool or something. - Will the PIR compress under the force from the pedestals? Perhaps you want another layer of OSB under the membrane? - I think it is costs more, but you can get tapered PIR which could replace your firrings and give you some extra thickness.

How are you earthing it? I did something similar and I had to install an earth rod for the new CU in the shed. I hit some rocks but it wasn't that bad. Took a few goes. I think in many cases you can export the earth from the house, but you need a large section cable, 10mm2 minimum I think. I have the shed running off a 16A RCD in the house (legacy thing), with a 10A RCD protecting the sockets in the shed. It always trips first in the shed, which is good, but I'll be upgrading the SWA at some stage so I can get some more amperage in there.

Thanks both. Tile and a half makes good sense if you could get one. I hadn't thought of that. I think I'll cut the two rafters and get the tiles lined up.