I'm going to be doing some cutting of the slab in my basement in order to put a bathroom in. There is plumbing under the slab and a pit with a tank in it, but it is probably 30 feet from where I want the bathroom. I understand I need to saw the floor, but there is roughed in load bearing stud walls in place (see this post for actual pics if necessary).

I need to go through/under these walls, so what do I do when I reach them? Cut the footers?

  • how deep a trench is needed? how deep is the foundation wall+footing that are under the slab that is under the 2x load bearing wall?
    – mike
    Oct 18 '13 at 2:51
  • deep enough for a 3" waste line. These are interior walls. At least a foot away from perimeter walls at all times. Oct 18 '13 at 6:00
  • If that is a load bearing wall, I bet that directly underneath the wall, under the slab, you will discover a foundation wall with a footer.
    – mike
    Oct 22 '13 at 6:58
  • The basement was roughed in by the builder, probably 8 rooms in 2500 square feet. I say they are all load bearing because they have double 2x4 headers, which I understand to be the standard indication of load bearing. If that's true, would they go to all that trouble to do as you describe with the foundation? Oct 23 '13 at 2:01
  • I am guessing you are talking about double top plates, which is not an indication that it is load bearing ... en.wikipedia.org/wiki/Wall_plate ... and ... thebuildingcodeforum.com/forum/residential-foundation-codes/… ... and ... arcxl.com/architects/detail?type=Spread+Footing+Detail
    – mike
    Oct 23 '13 at 5:39

One option is don't cut under the walls. Cut up to a couple of inches away from the wall and stop. Continue a couple of inches past the other side of the wall. Then you can just dig under the slab "bridge".

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