Hi! In a bit of a rush as our LVT is coming on Monday. Our door installers have left the floor area under the door open and there’s a cavity there, and a tiny bit of dpm under the window.

My intention is to fill the cavity with PIR kingspan foam boards, with a cavity closer on the top and a dpm tucked under the window one.

Is this correct and can anyone draw me a detail? (Where does the dpm go?)

Do I need to put some mortar down?

The LVT installers will be doing a self levelling screed on top.

We took out all the rubble here.

Internal block with some membrane on top, cavity, new window with some membrane under.

It’s about 10cm deep.

Edited 2 hours ago2 hr by LDNRennovation
Details

This is what it looks like in section.

If you're bridging the damp course lower down then use a membrane down the inner skin, across and then up the outer skin. If you're worried about thermal bridging then 25mm PIR against the DPM and backfill with concrete?

In a few window openings I've used just PIR in there but it takes no load so at a door reveal I'd want something a bit more solid.