Flood damage- hole under house by drain

[edeveuk]

Hi, We had a big flash flood and a hole has opened up in the floor at the edge of the house -outside (see photos). Luckily no water entered the house. Two of our block paving bricks seem to have disappeared down the hole (house was built in 1987)

Any thoughts on how I should repair? Should I be concerned about the foundations?

Two photos- there is a drain cover and pipe on the left.

 

[freddiemercurystwin]

Is that the bottom of the wall? It looks like a lintel that's been inserted above a drain run? A photo from further away would help?

 

[edeveuk]

Thanks @freddiemercurystwin

Downstairs cloakroom is above the gap you see so that makes sense