A long time ago some precast concrete stairs were put in place up against a concrete area (band) of the brick building. The filler material has given way, and there's a 1 to 2-1/2 in gap between the steps and the building. The only bridging material anyone can recall was a hunk of pipe insulation wedged in there and covered with an inch or so of patching concrete(!). You can go under the stairs to a basement apartment, so just brute-force filling the crack with concrete up against a joint filler won't work unless there's a way to keep everything from just falling through. The underside of the stairs has a corrugated look (big corrugations: 3 in wide (or so) recesses and protrusioons that extend a few inches), and the side next to the building is the last recessed area, so there's a depth of just about
3-4" from the top of the top step, to the bottom of the underside here. My thought was to glue a 3/4" joint filler to the building, make a long, thin, shallow trough out of something like hardware cloth and put it between the filler and the stairs, and fill that with an anchoring cement.Without being physically anchored, I expect this to eventually slide out, just as the last repair did, but it might last longer. Might not.
Any other suggestions?
Thanks in advance.