Ask a Tradesman
Groundwork & Foundations Question
Cracking in wall on a single story extension
Our house has a single story, flat roof extension added in the 70 or 80s and a crack has appeared in one corner going from the floor to about 3/4 the height of the room, then branching off at 45% towards the ceiling. The crack seems to be getting slowly worse and it's about 3-4mm wide. Externally I can see a hairline crack on the outside in the same position. The back wall seems to be have re-pointed in the last few years.
At the base of the wall the area below DPC to the ground seems to be crumbling mortar only. I've dug down a little to the footings and it looks like the brick is overhanging the footing by about 3 cm. Could this overhang be causing stress on the wall and causing the crack ?
Would it best to get a general purpose builder to check it out or surveyor, or structural engineer?
I would recommend you contact a local structural engineer which you can talk to the building control people of your local council to find out who are the best in the area and sensible in providing solutions.
Before the engineer arrives I would be inclined to carry on digging to establish the base level of the concrete footing not just the top. As a guide the footing should be at least 1m deep.
If your sub soils are clay and you have trees close by then this may be the root of the problem. The brick over hanging the side of the footing is bad practice but it doesn't account for the inner skin having the greater crack developing.
The engineer should be better positioned to give you the analysis of the problem and a practical solution.
Hope that helps
Answered 1st Oct 2013