Large crack and uplift in garage slab

[patrickstar]

Hi,

My detached 2 car garage has 3 large cracks and uplifting (about 1"-3" at crack) . Whenever the garage was built (perhaps around 1960) the slab was poored w/o rebar. It appears to me that the 3 walls have pushed down (I say this because of the sloping from the crack down to the wall) on the concrete around the perimiter (which doesn't appear to be any thicker then the rest of the slab) and the pressure caused the cracks. There are 3 cracks that are parallel to the 3 outside walls.

I'd like to turn the garage into a woodworking shop but I need to get the floor smooth and level. I have some ideas on simple fixes to tearing down the garage and starting over, but I am looking for ideas and suggestions.

I had originally thought about jack hammering out the concrete within the perimeters (leaving a little bit near each wall) and then repouring with a metal mesh...thoughts?

Thanks. Some pictures:

http://lh5.google.com/jonathanwicks/R1w97x89CoI/AAAAAAAABzE/vu5FSfXm60I/s144/Dec09_0001.jpg

http://lh4.google.com/jonathanwicks/R1w99h89CqI/AAAAAAAABzU/cc3NeZoq3Zk/s144/Dec09_0005.jpg

http://lh5.google.com/jonathanwicks/R1w9_x89CsI/AAAAAAAABzk/1YlDL6hVTUE/s144/Dec09_0007.jpg

http://lh6.google.com/jonathanwicks/R1w97B89CnI/AAAAAAAABy8/vE5jx_ffPec/s144/Dec09_0002.jpg

http://lh3.google.com/jonathanwicks/R1w96R89CmI/AAAAAAAABy0/CAYi50X-1ZA/s144/Dec09_0008.jpg

[Wgoodrich]

Look at the wall and the sloped floor. Suspect the wall is undamaged showing not sunk yet the floor is sinking. If the wall is not showing damage or sinking it is your floor not your wall. Floors normally pour to the wall but not on the wall allowing the floor if undermined to sink. Garage floors commonly crack from the past and even some in the present. MOst common cause is gutters not getting the water flow away from the house thus softening and washing dirt out from under the garage floor causing a void under the floor inviting the crack. Some caused by chipmonks digging and making a home under the garage floor if the footer is not at least 24" deep carrying the dirt out from under the floor again causing a void inviting cracks. Again if you find parts of your floor heaving up along the wall the footer was not installed frost protected matching the equal potential of the attached house being frost protected. Frost then works horizontally under the footer heaving the floor up.

If you are making a living or working area you might consider installing plastic vapor barrier sheeting on floor then 2" styrofoam with framing treated floor joists above the styrofoam. The styrofoam will dent and mash if heave still is present allowing a new wood floor to stay straight. Also raising the floor above garage more even with the house floor elevation. You may insulate above the styrofoam with non paper style fiberglass insulation between the floor joists to increase comfort in that work area.

Hope this helps

Wg

[patrickstar]

Thanks Wgoodrich for the reply.

I live in Austin TX so I'm assuming its not due to the ground freezing.

The garage doesn't have gutters so it does seem likely that the dirt under the walls has compressed or been washed away causing them to sink and the floor to rise in the center. Btw, I can get my hand under the concrete where it's rising.

So for the styrofoam idea, it would be installed right over the cracked garage floor then right? How would I get the styrofoam to conform to the current floor slope and crack?

Btw, I posted some pics in the original post in case they help.

Thanks!

[Wgoodrich]

Is this a pole building style construction or is it a stud wall building with a footer. If with a footer how deep is the footer. I am now understanding this to be a detached stand alone building.

The pictures make it hard to tell but looks like a part of the floor stayed the same original elevation and two parts of the floor sunk into the ground at differing speed of loss. Is this correct ? Does the building walls show any sinking or are they still straight and unchanged ?

Wg

[patrickstar]

Its a stud wall. I am not sure about the thickness of the footer I'll have to check later. Yes it is a detached garage.

Yes the middle of the floor seems to have stayed relatively in place. Then there are 3 sections, left, right, and back that have sunk all at different rates/degrees.

Yes, The walls have shifted. The left and right walls are leaning a bit. Currently there isn't anything to keep the structure rigid (just siding on the studs), so if you push hard on the right side it moves. I was going to install plywood sheathing in the back to make it more rigid.

I dunno, perhaps its better to tear down and start over. I was hoping there would be some alternative short term fixes that could last until I redo the garage properly. If the fixes start to approach the cost to build new though...

[Wgoodrich]

What is happening to this structure is very intrusive. I believe it can be saved but it would take quite a bit of step by step guidance. However to give you accurate advice we need more pictures. Can you stand in the middle of the floor with your camera and use lights to light up each wall one at a time and take pictures of all four walls showing construction from top to bottom ? This will help us help you accurately. I think this can be repaired correctly with cost factor staying about the same as the floor framing we were talking of. Not sure that is a good idea at this point due to compromised structural wall strength. Need pictures of the walls and maybe a couple of the roof/ceiling too. If you could provide a couple of pictures of the walls from the outside showing the contact with earth also.

Curious

Wg

[Fischer]

Don't give up the ship yet. From what I can see of the walls, it doesn't appear that there's any crossbracing. Running let in bracing on the interior walls is not that difficult and it will keep the garage from shaking. Couple that with the rafters crossbraced, and you should have a stable building to work from.

As WG requested, send some detailed picures of the walls. There's a couple of solutions for the slab, all of which would entail removing it and starting fresh. I think you're not probably lucky off without bar and mesh in the floor. It would just be harder to remove it, and it probably wouldn't have saved it with all the expansive pressures from the side walls sinking and the mounding in the center.

If you can borrow a laser from someone, shoot a line around the perimeter of the walls, and measure to the bottom plate and include those measurements with the pictures.

[Wgoodrich]

Without seeing those pictures of the wall inside and outside we can not be sure but it looks like the footer has been compromised with dirt working out from under the footer causing your damage. If I am correct after seeing the pictures I was intending to do as fisher was leaning on about cross bracing. This garage I believe can be easily cross braced from the inside. Moved off the old footer and a new footer and floor installed then reset the building. The cross bracing would allow this building to be rolled off the old footer using pipes or can swing off the footer after picked up by a crane. Either way it is not hard or expensive to do. Much better than destroying and building new.

We will see after the pictures

Wg