I want to pour a 16 x 22 patio from my house foundation (slab) and encasing 3/4 sides of the storm shelter. The contractor states he will drill and place rebar dowel every 2 feet into the foundation AND storm shelter. I have concerns with him messing with the storm shelter. I believe it has 8” wall. Does this sound like the way to do this. I sure don’t want to mess with the integrity of the shelter or foundation. Any guidance appreciated. enter image description here

  • The storm shelter is the type where part is in the ground and the door and top is above ground.
    – MOgirl
    Commented May 5, 2021 at 17:15
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    This sounds very typical. The only downside I can imagine is if the storm shelter is block (rather than poured), then the rebar dowels don't do much. Commented May 6, 2021 at 14:39
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    The rebar is there to keep everything in place for years to come. I have done this many times and not created problems, are you worried about leaks in the storm cellar? With the slab graded away from the house it should help keep the cellar dryer.
    – Ed Beal
    Commented May 6, 2021 at 14:58
  • Freeman, I got my pic added. Aloysius, as you can see it’s a formed pour unit. Ed I was more concerned with disrupting the integrity of the storm shelter and foundation....expansion causing future cracking leading to leaking. I’m a worrier.
    – MOgirl
    Commented May 7, 2021 at 15:35

1 Answer 1


I don't consider it appropriate to hang slabs on foundation walls. First, it doesn't keep the slab up. If the interior of the slab settles the slab will almost certainly crack and sag, creating a saucer with raised edges. Secondly, it threatens the foundation walls with undue stress.

I can see connecting multiple slabs with such dowels, but not foundation walls. My $.02.

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    Your 2 cents means a save of thousands to the OP for drilling and dowelling. In this case, a floating SOG (slab on grade) with thickened edges suffices the purpose. The important things are excavation and disposing of existing clayey soil, replacing it with free-draining gravelly material, and with adequate compaction. An expansion joint at where the slab gets in touch with the existing concrete is recommended. The joint joining the existing house wall/foundation shall be sealed to avoid water to get through.
    – r13
    Commented May 7, 2021 at 20:56
  • So will he form up at the house foundation and around the storm shelter? And then seal between new and old concrete for waterproofing?
    – MOgirl
    Commented May 8, 2021 at 19:16
  • Those are new questions not really appropriate for a comment. (Take the tour if you haven't.) If you opt for an expansion joint at the foundation that ribbon of material could act as a form. Otherwise, it's usually snap a line on the wall, pour to that, and run the edger against the wall to form a nice radius (fillet). I don't consider the battle to keep water out of that crack worth fighting. YMMV.
    – isherwood
    Commented May 9, 2021 at 0:11

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