Insulation cap cavity wall of splayed bay patio doors

[Craabonn]

Scratching my head on how to appropriately finish the splayed cavity wall of my patio doors (See below).

I want to close cavity along its opening, and not block cross flow of air. The opening ranges from 50 to 60 mm. Originally, uPVC was installed on the upright reveal, and a lipped window sill that was not sealed. There were points where the cavity vented into the living space. A wood board was placed on top of the exterior and interior wall, over the cavity, with no moisture protection and was rotted. The whole space had significant damp issues which have been rectified.
Is it sufficient to wedge fit PIR, and close gaps with expanding foam. I have PIR of suitable thickness on hand. Am I right in thinking:
- Some sort of moisture protection is not needed for wedge fitting the PIR? I will aluminium tape exposed PIR.
- the space behind the PIR is open and freely vented into the suspend floor space and external wall vents
- the cavity has been cleared.

Or, Would really be a lot easier to get cavity closers? I presume, saving me a lot of hassle.

Afterwards, I assume my best option is to dot and dab plasterboard to cover the upright reveal? on this part, does the PB tuck in between the PVC door frame and masonry, with space so it does not butt up against the exterior leaf?
- I would need to take back some of the mortar on the reveals for space to dot and dab, and to try to meet the plaster corner.

 

[Deluks]

Looks like you could knock down and rebuilt that inner leaf, then you can fit the insulation with ease, and tidy up the brickwork to take a cavity closer. You only need 10mm between outer leaf and the back of the insulation.

Using lightweight blocks or even a stud wall would increase the amount of insulation you could fit.

 

[Craabonn]

Uhh, you are right. I thought of doing that initially at the start of the reno, but was advised by two separate people not to, and to just crack on with the original intention of fixing the joists..

Seriously, the effort I went through trying to clear the two cavity walls, and its still a it clogged. The inner leaf is a bit of a state, several cable ties are rusted after being buried in build up, points of loose bricks and mortar on both sides.

The room needs to be put back together within the week for my Sons birthday. I'll leave the cavity opening for now.

Afterwards, I'll do the wall with the floorboards in situ. On a similar topic, since posting this thread, I've started to build-up the inner leaf wall-threshold to the door, but it still requires two more brick layers. Instead of continuing with the original bricks, I could switch to lightweight blocks or frame it? I did a quick mock up below, thoughts?

I'm aware the DPC under the door needs some TLC too.

I've be re-using the old bricks and my wrists are ruined haha.

 

[Deluks]

If time is a factor (it seems it is) just put some 50mm mineral wool cavity slab in there, using your hand and a pokey stick. Make sure there are no gaps (cold spots)
Then fit your cavity closers and crack on with the rest of the room.

Forget PIR unless you remove and replace the wall.
The large glazed area of the doors means it's not worth fretting over u values in that small section of wall.