Floating Slab Crack

[Greg Clemmons]

I found this crack along the outside edge of the interior portion of the slab, its about 22' long by 1/4"to 3/8" wide. The slab is what i have always called a floating slab, perimeter is brick with footer and slab is raised about a foot above grade. There is no signs of settling of footings/brick just the slab itself. There are no cracks in the walls or ceiling, wood siding on the exterior shows no signs of settling. The slab itself has no other cracks.

I have never seen this type of slab crack, has me just a little confused as to how the slab can settle on the edges and not crack elsewhere.


Anybody have any ideas as to cause/ repair



Thanks,

[imported_John Smith]

Hire a home inspector in your area for a thorough evaluation.
Dont know about your area, but in mine, I see problems around the perimeter (or edge as you say) before I ever see any damage farther towards middle.

Our soils tend to hold moisture like a sponge, but once they dry up, they are just like a sponge that becomes thinner and the edges go first. Once the edges dry up, settling will occurr and cracks due to differential settlement will start. This year was particularly brutal in Houston. Maybe I should start contracting foundation crews, but heck they are all too busy and I wouldnt find any help.

[Billy Stephens]

how the slab can settle on the edges and not crack elsewhere.


ideas as to cause
,
.
Two Pours.

Interior Slab was Poured before Exterior Patio.

Slab Layout was short on Interior or Concrete delivery was light and short poured on the Interior slab. Resulting in a cold Joint.
.

[Greg Kelly]

Hi Greg,
If the slab was poured against or over the exterior foundation wall, rather then flush to it, with proper compaction and reinforcing mesh, the likelyhood of a crack forming and becoming an issue would be reduced. Same thing happens if you pour a basement slab (I'm in Canada) flush to the top of a footing. Not a good situation for ceramic tile or similar floor finish.

Greg