Nickfromwales

Sorry. Typing whilst working. A decent timber yard will just slice up and deliver what you need when you give them the length and fall ?

They'd be 8m long ( when you join two bits end to end ).

Ok lol. So the slope is down the 8m run ? If so, the firring pieces will be fixed down on top of the joists starting from 2" and tapering to nothing.

Just draw another sets of 4" timbets over the top of the ones you already have, running perpendicular. Then those run from 4" to 2" over the 6m to create the pitch for the flat roof sarking boards. ?

The terminology is important. Vent = open to atmosphere AAV = sealed to atmosphere but opens to allow air IN if a vacuum occurs within the stack. ?

What's there not to like ? I surrender. ?

If your at 400 centres with the joists and you use a firring piece that is 2" at its thinnest then you'll only have to noggin the last couple on each piece. Once it's sarked you'll be rock solid. Screw the sark boards, not nails .

Perpendicular over noggins .

The firring pieces would sit whichever way you want the fall.

A vent is required to promote ventilation of the sewer gasses to atmosphere.

You'll have a sloped ceiling then . Much easier to whack everything in flat and put firring pieces on.

? 'ng good, but I'm a bugger for lining up the noggins and dovetail nailing / screwing instead ofcend fixing the staggered runs. A treated timber would make life easier for pinning the joists and would give you something to fix a pelmet to if that would be aesthetically pleasing. It may cause issue though if you intend rendering up to a soffit board as there would be a 2" gap of timber between the blockwork and the soffit.

Yes, PIR aka most rigid insulation boards. Colotex is a brand of PIR ?

I'm just wondering if I'm feeling cruel enough to make you show the noggins . Looks good. With the PIR and full full wool in the voids that should be a decent make up. Dont forget to dig the slot in the ground for the swim-jet. .

Best to go an lay some larch out now so it can be conditioned to match when you box it in?

Can the main MVHR inlet be ducted to a remote filter housing, located conveniently for regular access / maintenance? Just thinking for future installs if the filters can be mounted where they're easily accessible without dismantling the main unit then that would be preferential. Obviously not miles away from the unit, but as long as the duct wasn't in excess of the length of inlet stipulated by the manufacturer, or was enlarged to have the same ( equal or < ) resistance then I think that would be a good discipline to adopt. @JSHarris, any further thoughts on your downwards 'inlet snorkel' ?

Bingo

Very sorry Ed, but its BH policy that members who dont yet fully feel our pain are politely reminded not to encourage this madman. Were trying to get it tiled and grouted before xmas. Dont ask which xmas PLEASE !

He shoots.....he scores, lol. Yes, that's the kiddy.

It's another day at the asylum. "Carry on", we've come this far .......?

Nope lol. Draw it with the 8x3 vertical so sandwiched between the joists. .

Or some big ass firring pieces over the joists, run t'other way, with PIR cut in between ?

Ok. Your pic shows 2x 4m timbers making up the 8m span. That I assume means your showing the break in the run on top of the 6m steel ? You cannot have the break there unless the joints are mechanically fortified. Regs will ask for a certain distance for the joists to sit on the steel so the ends on the joists don't compress under the weight. The 8x3" would be in the middle of the steel, sat on top, running along its length and positioned vertically. The joists would then be made off into joist hangers affixed to the 8x3. Clear as mud ? I'll do a pic if your not sure.

Already suggested but issues with the cold bridge unless a lot of insulation goes over it.

Raised ? What for ?