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The concrete just collapsed!

757 Views 17 Replies 12 Participants Last post by  Fishindude
So we are working on converting a screened in patio into a four season room.

The Plan was to build up the outside perimeter with one course of block on top of the existing pad and and attach ledger boards and joists to meet the floor height of the existing house. Basically deck over concrete.

The engineer required us to add footers around the perimeter, to support the block and additional framing.

Here’s when the fun began:
While digging out the perimeter we found an existing footer. It was in bad shape, top course of cinderblocks were disintegrated noting but dirt. Once we dig out and expose the full footer the concrete pad cups/collapse in the middle. Not the perimeter just the middle.

After cleaning the Sh*t out of our pants, we discovered the was no dirt under the pad. The voids are any where between 5”, 2’ and 3’ in some places

My guess is water over time washed the dirt out. But where did it go?? In one of the crawl spaces in the basement has a lentil in the back right hand corner that creates and opening under the pad (5’ down). You see the dirt but no signs of wash out.

As of now we are planning on removing the pad, pouring a new footer/stem wall and then pouring a rat pad to cover where the pad was.

Any thoughts if that’s a solid plan? The change order will not be cheap because it’s a tone of manual labor. Chipping the pad with nothing under will be a pain not to mention dangerous.
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Did you brace that corner with 6 x 6 posts? I’m not saying it’s overkill, but I’d sleep under that.
We did use 2- 2x6 and 2- 2x12. Figuring we would need to rebuild the stem wall in the corner. So spread the load out for the roofline.
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My reply wasn’t helpful. I don’t know anything about concrete. Any reason you couldn’t mud jack that? I’ve seen lots of driveways lifted with injection foam.
We thought of mud jacking but I’m not confident in the compaction of the dirt underneath.

We drilled a bunch of hole and dropped in rebar to see where the dirt started. We the pushed the rebar further in about 6”-10”. the compaction is not great.
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Hopefully one of the demo experts will weigh in, but my instinct would be to use a concrete saw to make controlled cuts and breaks from the outside corner in.
With the pad already collapsing the issue I have with using a concrete saw is “kick back”. I have seen plenty of saw kick back when the concrete pinch’s the blade sending the saw flying back up to the operator. Having a diamond blade stuck in your head makes for a bad. If I was on solid footing I would totally agree.
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