Garage floor problem

[Harding]

Hello everyone. I've been lurking for some time and would like to get some opinions on my problem. I have a detached garage 22 X 30 that was cracked down the middle when we bought the house 7 years ago. Looks like a 5" slab on grade with no footings. Tried the Slabjack method 4 years ago, (I wish I had found this site before I wasted that money). They pumped 3 yards under the slab to stabilize but it did not raise droppped section. The middle of the 30' wall has dropped about 3-4". Seeing some of the projects guys are doing on this site makes me think I can tackle it on my own this time around. I am starting to get a plan together and would like some guidance. The plan is to build a 12x12 footing along the side and back to jack and shim from until it's back to level. Cut down the center and remove old slab and concrete that was pumped under. Backfill with 6-8" of gravel and repour the slab the rebar drilled into the new footing. How does this sound? Suggestions please...

 

[cowboyjosh]

Just tear the entire garage down and start over.....

 

[Commando]

Do you have any pics, was trying to visualize in my head.

So is this standard framing on a flat pad? Also have to wonder what caused the dirt or gravel whatever they put under the pour to settle or erode that much.

Depending on your budget you could get a house mover in there to lift it up and repour with a footing. They do stuff like that near me all the time to get houses above the flood levels.

 

[NUTTSGT]

Some pics would really help.

If the floor has dropped 3-4 inches, there's a reason why it dropped. That reason needs to be found and fixed.

 

[bazzateer]

Just tear the entire garage down and start over.....

Agreed!

 

[Milton Shaw]

If you go the route of pouring over the slab, rent a bobcat with hydraulic breaker and break up the old slab and let it settle down over the earth that's sunk away from the concrete. If you don't do this before you pour the new one it will crack and sink also. Then get the movers to lift garage and pour new slab and combined footing. In north Georgia you are not worried about frost damage so the footing doesn't have to be very deep. The hydraulic breaker takes about 1 second a hole to bust the slab up into 3-4 inch rock pieces that can be either left in or thrown out and covered up. Don't just break it into 3 or 4 foot pieces that don't solve the problem as they won't settle and fill the void. I have used one and its so much easier than hand demolition breakers, the only thing on you that will get tired are your ankles from moving the pedals on the bobcat.

 

[Harding]

Thanks for the replies. I'll work on getting pictures up this weekend. I think the sinking problem is from being built with NO site preparation. The driveway slopes slightly toward the garage and water drains around the side and off the back of my property. Problem most likely started when previous owner began dumping grass clipping, leaves and small branches next to the garage and water would pool. I cleared all that out when we moved in but damage was already done, or set in motion, as the slab was cracked by this point.

 

[Harding]

Here are some pictues I found of my garage. Hope these help out with any ideas.

 

[Falcon67]

I had a similar issue with my old shop, not as severe as what you describe though. I did not fix it before we sold the property. My plan to fix the mid-long wall drop was to trench down that side, install hydraulic jacks along the edge bearing on a steel "lintel" and pads. I would have had to raise the center of that side about 1~2". When I got it back up and the mid-slab crack sorta closed up, I would have poured a footing in place with the cheap HF jacks just locked in the pour. Mine sunk from 1) no footing 2) run off that settled the earth on that side of the building before steps were taken to route the water away from the building. It happens.

For your deal, I think you are heading in a decent direction. If it was me, my idea would be to jack the wall back level and install a temp wall to support the joists inside the building, some small distance from the existing wall. Then take out the slab edge under the wall, set up the footing and pour to support the wall. Once the wall is secure, remove the temp support and do what you like to the rest of the slab. Gutters and water drainage should be looked at while planning the footing. You might need weeping tiles, french drain, etc

 

[Commando]

From what I see of your driveway, you may have all that situated in the spot where the runoff flows through. Pavement all cracked, may be better off with gravel to help the ground absorb moisture.

Sorry to head this in a different direction, but the initial issue needs to be identified or it will happen again.