What is this and how do I fix it?

[les_danger]

In the process of fixing something else what looks like the threshold beneath my patio doors caved in.

On the front side of this is an air brick, which i think was badly damaged and so has been patched up with a temporary cover.

So i suppose there are no bricks directly supporting the bit that ...collapsed.

Anyway interested in: what this is actually called for the sake of describing it; how one would go about fixing it diy; or what kind of trade i need to sort it. I'm going to get the door replaced eventually but that might be a year or so off.

Cheers

 

[foxhole]

Maybe remove exterior vent and more pics .?

 

[accelerator]

You could just remove the bits of mortar that have fallen down, and then cut a piece of wood to bridge over the gap (treat the wood with preservative). It's just giving you additional ventilation.

 

[les_danger]

Right you are, here's some more pics with the temporary air brick cover removed.

Going in a bit further it seems like it was supported by this wood which has given way

Top down inside view

But what i don't get (along with lots of other things) is where was this wood supposed to dock into the brickwork? If i look at the brickwork to the side where we've got the floor boards up there doesn't seem to be a wooden sill running on top of the brickwork, at least not that i can make out.

What do you reckon?