Slab on Grade Construction over demolished (lowered) existing foundation wall
Slab on Grade Construction over demolished (lowered) existing foundation wall
(OP)
To save money and disturbance, I am looking to construct a new slab on grade over existing foundations and foundation walls. I would like to leave the existing foundations and walls in place, but demolish the walls to some distance below the bottom of the new slab, install compacted granular base material (over the remaining wall), and then construct the new slab on top of the base. My question is, what is the recommended minimum depth of demolition for the foundation walls below the bottom of proposed new slab on grade to avoid cracking issues (the remaining foundation wall providing a rigid or pivot point below the slab)? Is 12 inches sufficient? 16 or 18 inches? Or more?





RE: Slab on Grade Construction over demolished (lowered) existing foundation wall
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RE: Slab on Grade Construction over demolished (lowered) existing foundation wall
RE: Slab on Grade Construction over demolished (lowered) existing foundation wall
RE: Slab on Grade Construction over demolished (lowered) existing foundation wall
RE: Slab on Grade Construction over demolished (lowered) existing foundation wall
RE: Slab on Grade Construction over demolished (lowered) existing foundation wall
one solution is to reduce the settlement of the surrounding area to match that at the foundation wall. That might mean overexcavation, backfill and recompacton in order to improve the subgrade so that it all settles uniformly and has a similar stiffness. Very expensive option
alternatively, might be better to not over do the subgrade improvement and compaction in this one area and attempt to match settlement and subgrade modulus to that of the surrounding area. Removing the concrete structures to a deeper depth will accomplish this possibly without the need for granular backfill and special compaction requirements.
Or just reinforce the slab and allow it to bridge the small soft spot.