Cavity at door threshold

24 Nov 2022
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United Kingdom
I know this has been posted many times before and I have spent time looking at those threads. I'd just like confirmation from those more knowledgeable that what I'm about to do is correct.

The builder has left me a shell of a garage and what will be a utility room on the back. The floor levels in the utility are high to match the rest of the house. The back door from the utility room to garden has a deep (one block and 5 courses of brick) and wide (120mm) cavity. The DPC is 3 courses down from the sill of the door.

My plan is to knock away the first row of bricks from the inner skin and line the trough with a DPM pocket, then connect that DPM to the DPM running under the concrete slab. I will then fill the DPM pocket with concrete and a bit of PIR against the external leaf and bottom. I'll then screen the floor and trim DPM at the finished screed height.

Is this correct or is there a better way?

I assume I can do the same thing at the other doorway from the utility to the garage.



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