"minor" underpinning

[sm_jamieson]

I have to fit a rest bend / stub soil pipe for a new toilet right against the brick wall between the hallway and the kitchen that is holding up my stairs and some of the first floor joists. This wall it turns out does not have 2ft deep foundations like the rest of the house, but is 1ft down and begins with 2 rows of 9" brick direct to the ground, with the half-brick wall above. I will have to dig down below this foundation depth to fit the rest bend and drainage. Now, not normally a problem, but since the wall is only 1m wide and would need about 300mm wide trench for bedding, I'm worried about stability. Should I perform some type of underpinning operation to this wall ? Hammer in some sort of metal plates ? Any thoughts ? Thanks, Simon.

[sm_jamieson]

Well, what I am going to do is buttress the foundations, a good compromise with less risk. If the ground cannot move sideways from under the founds, its safe. I'll pour two lumps of concrete leaving a suitable "gap" for the drainage pipe. When the pipe is in place I can set this in concrete thus effectively buttressing the whole wall. I can probably get away with 250mm gap, i.e. 75mm each side of the pipe for bedding. Seem OK ? Simon.

[JimK]

I would think abt maybe not bedding the pipe in concrete - what if their is some future movement/settlement (caused by anything not necess your new pipe) - what effect that would have on the plastic/ clay drains anchored into it all with concrete.....3 inch each side should be plenty for pea gravel - if BCO involved he will advise what he wants for all of this....

Cheers JimK