Victorian damp question

[huddc001]

Renovating our Victorian London terrace. The front garden was built up way too high so we have dig down to below the air brick and plan to lay permeable membrane and then cover with gravel.

We have come across what looks like an old drain in front of the air brick (photo attached) but we can’t work out what it is or why it’s there!

Any ideas would be very helpful!

 

[Lower]

Looks like once upon a time there someone constructed protection around the airbrick with bricks to maintain airflow, probably to allow soil or gravel to be built up higher than the airbrick level.

 

[huddc001]

Ah thank you that is very helpful! I assume if we are removing the soil to below the air brick we can probably remove these?

 

[tell80]

Best practice will involve you removing back to bare masonry all the render, and the sand & cement plinth from the lower bay.
Dont touch the stone brackets.
The air brick & its brick surround will also have to be removed - the air brick is useless because its been installed too high. A/B's should be installed below the FFL.
If you have a suspended floor behind the bay then you need to install a/b's across the front elevation to vent the underfloor area.

You will probably need to dig the garden soil out deeper - look for a DPC in the bay wall: it might be slate or bitumen or not even there but look.
Notice the height of the neighbour's garden - be careful not to collapse the boundary.
Do you have any signs of damp inside the front bay and elevation wall?