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I might buy this house and have never lived there.

The porch has an big air space of maybe 4 feet underneath the slab. Some of the rebar at the bottom edge of the slab is visible when peering in. The rebar is not the small round stuff; it's more like the T-shape metal 'fence post' thicker design.

Of course, the crack also needs repair. There are other smaller, less visible cracks.

The hole has been there for a long time so the concrete around the hole feels a tad crumbly.

The porch is perhaps 6 x 20 feet. I didn't measure the slab thickness, but it's probably 4-6 inches. There is a basement block wall towards the back side underneath.

  1. If it is not a good idea to use a strong concrete patch, why not?

  2. Otherwise, if it is not a good idea to open up the hole a little and fill the huge air space with something, perhaps a concrete slurry, why not?

  3. How about using a Trex or wood product (or some stamped design) to re-cover the porch after patch since it would otherwise look ugly?

Thanks.

hole in concrete porch

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Knowing that the earth has subsided from underneath the porch (and it's all cracked, anyway), I'd ask for a discount along the lines of what it would cost to bust it up, throw it away and re-pour it.

I bet I could sink that porch into the basement with a hammer. Move on to the next house, unless you both want to play the discount game.

If you're going to call out a truck to pour 12+ yards of concrete, you might as well have a nice, entirely new pour. If we really want to get into how to 'fix' this, we'd need a lot more pictures and knowledge of the substrate in this particular situation.

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Assuming the slab is generally structurally sound, a patch for this hole should be fine. If the structure is OK, the chief concerns are safety (so nobody trips over this hole) and sealing of cracks in order to prevent further moisture seeping into the concrete and causing further cracks during freeze/thaw cycles. You can use concrete for the big hole and patch long thin cracks with a polyurethane-based self-leveling concrete crack filler.

Dumping a lot of concrete under this porch is not a good idea. I doubt that the gap under this slab is the earth subsiding under the slab -- I'd guess it's a raised slab held up by side walls, and is designed to have a gap underneath. Filling that gap with concrete without preparing the ground below to hold all that concrete will likely not provide a long-term solution, and will add pressure on the side walls that could damage them. If you have structural problems, do what @Mazura suggests and replace the porch (or the parts that are problematic).

Following repairs, you can certainly cover the porch to disguise them. You can paint it with an appropriate paint or specialized concrete/deck coating. You can put on a layer of trex or wood decking, ceramic tile, outdoor rugs, rubber tile... lots of options.

Again, it's hard to tell from just this picture if you have serious structural or just minor problems. It's normal in purchase negotiations to have an expert come and give you an estimate - you might want to call out a mason.

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