Repairing Sunken Concrete Floor

[spazzyfry123]

Hello all,

I'm a bit of a lurker on here, but I figured this corner of the Internet would result in the most help.

I purchased a home a little over a year ago that is based on a crawl space with an attached 20' x 20' two-car garage having a concrete slab for the garage floor. I've been changing some odds and ends around the house since the purchase, and I'm finally ready to start digging into the garage. My intentions (looking into the garage from the driveway) are to have my car parked in the stall to the left; work bench/cabinets, peg board for tools, etc. on the back wall; beer fridge and flat screen on the right wall; couple chairs facing TV with table in the right stall. Luckily I have a separate building to the right of the house which I keep all paint, lawn equipment, etc. so that I can keep the garage tidy.

While I've already acquired my cabinets and all for the back wall, I have an issue with the floor that needs to be addressed before I can really start much of anything. The floor is sunken in right in the center by 3 cracks that make a bit of a "Y" shape - each of the angled portions coming from the corners of the garage closest to the house and then meeting with the straight portion of the "Y" towards the center of the garage floor which then goes to the garage door area of the slab near the driveway. You can see where the previous owner has done something to try and seal the cracks, but nothing appears to have been done to alleviate the, to put it nicely, settling.

I am trying to avoid breaking up the slab to re-pour if at all possible strictly because of the costs involved. The house was built in '84, so I'd say it's "settling" is pretty much done. What are my options? In talks with my contractor that's helped me square away some electrical issues amongst other things, he suggested I look into something that is self-leveling. While I like the idea of its simplicity, I'm not keen on its load ratings. Considering that I ultimately want to use the garage as a garage and have my car in there (~3400lbs I'd imagine), how good is this self-leveling concrete in this regard? Should I go this route, would it be ideal to use tiles (ceramic, plastic, vinyl, or what?) to help spread the load? Or am I able to keep the "bare" floor for structural reasons and use an epoxy or similar for aesthetics?

What my options oh wise ones? I miss not having a garage/man cave - although I am a bachelor, so I suppose the whole house is my man cave

Thanks!
-Tyler

 

[Bondo]

Ayuh,.... Welcome Aboard,... Got any pictures,..??

How much drop/ fill are We talkin',..??

Over how big an area,..??

Which way to the pieces pitch,..??

 

[LB-1911]

How much drop/ fill are We talkin',..??

Over how big an area,..??

Which way to the pieces pitch,..??

attached 20' x 20' two-car garage having a concrete slab for the garage floor.

The floor is sunken in right in the center by 3 cracks that make a bit of a "Y" shape - each of the angled portions coming from the corners of the garage closest to the house and then meeting with the straight portion of the "Y" towards the center of the garage floor which then goes to the garage door area of the slab near the driveway.


I am trying to avoid breaking up the slab to re-pour if at all possible strictly because of the costs involved. The house was built in '84, so I'd say it's "settling" is pretty much done.

What are my options?

What you don't want to do is the best option - Remove it -

 

[astroracer]

Check into mud jacking. I don't have any idea on cost but it may be an option.
Mark

 

[James-W]

Are you sure the reason the floor sunk is strictly due to settling? Is it possible you have other issues that is causing this problem?

 

[spazzyfry123]

Ayuh,.... Welcome Aboard,... Got any pictures,..??

How much drop/ fill are We talkin',..??

Over how big an area,..??

Which way to the pieces pitch,..??

I would say at its deepest relative to the "normal" plane, it would probably be 2.5" ÷ 3". As far as area, I really haven't done the math just yet. Weighing my options first to find the best approach.

What you don't want to do is the best option - Remove it -

I haven't even attempted getting a re-pour quoted. With what little info I've given, about how much do you guys think a re-pour would cost?

While I realize that it's certainly the best option, this isn't a house I'm planning on staying in eternally. Of course I want to do things the right way, but if I can save a few bucks to do what I need for, say, the next five years.....

Check into mud jacking. I don't have any idea on cost but it may be an option.
Mark

Sorry for the Facebook link, but a friend of mine showed me this a few weeks back. I know nothing about it, but sure seems like a (potentially) great idea...
https://www.facebook.com/video.php?v=825688657477299&pnref=story

 

[spazzyfry123]

Are you sure the reason the floor sunk is strictly due to settling? Is it possible you have other issues that is causing this problem?

As a new (read first time) home owner, I honestly have no idea. This was more of an assumption on my part more than any actual facts to back it up. What other issues could make something like this happen?

 

[Nermal43]

The answer is, "it depends." On a lot of things. Pictures would be a big help. I have an old garage space that is 24' x 24' it had a large crack all the way across in the middle and a drop of 2+ inches from middle to side. It had finished settling so I cut out the crack, dug and compacted and put in gravel and poured to even it out. No problems in the 3 years since. About a $100 fix v. $5-8 k for a new slab.

 

[mnavillus]

please post a few pictures....thanks

 

[JACDes]

Too many unknowns

but best guess is the slab sunk and cracked due to poor sub-base preparation.

another possibility is freeze / thaw damage which goes back to poor sub-base prep.
probably not an issue in GA.


mad jacking and self leveling patches are not going to correct the sub-base.

 

[pstnbly]

Tap around with an engineers hammer and listen for hollow sounds. If there are hollow spots you need to determine the reason. I have seen water migration undermine slabs and no amount of mud jacking will solve the problem until the water is dealt with. The best solution for the surface issue would be saw cut out the bad area, fix any sub base issues, dowel and repour.

 

[spazzyfry123]

The answer is, "it depends." On a lot of things. Pictures would be a big help. I have an old garage space that is 24' x 24' it had a large crack all the way across in the middle and a drop of 2+ inches from middle to side. It had finished settling so I cut out the crack, dug and compacted and put in gravel and poured to even it out. No problems in the 3 years since. About a $100 fix v. $5-8 k for a new slab.

Yours sounds like a similar scenario to mine. I don't know what's going on underneath the slab, but the damage done sounds familiar.

please post a few pictures....thanks

I will try to get some pictures in the upcoming days. I have a lot of odds and ends in there right now as I was getting ready to patch some holes in the walls. So of course, everything in the garage is pushed towards the center (on top of the issue) to be away from the walls.

Too many unknowns

but best guess is the slab sunk and cracked due to poor sub-base preparation.

another possibility is freeze / thaw damage which goes back to poor sub-base prep.
probably not an issue in GA.

mad jacking and self leveling patches are not going to correct the sub-base.

The slab had no pressure release cut into it like you would generally see. It was originally done as a solid piece.

Tap around with an engineers hammer and listen for hollow sounds. If there are hollow spots you need to determine the reason. I have seen water migration undermine slabs and no amount of mud jacking will solve the problem until the water is dealt with. The best solution for the surface issue would be saw cut out the bad area, fix any sub base issues, dowel and repour.

Fixing the sub base sounds like essentially tearing out my entire garage floor (the three cracks spread from one side of the garage to the other). Is this the case?

As an alternative, is the self-leveling concrete capable of high loads?

 

[Kwjeep]

How about this?

 

[JACDes]

not having control joints would not have caused the slab to sink.

concrete will crack:

If kept restrained from movement aka "expansion" (lack of control joints)
shrinkage cracks when curing aka "contraction" (lack of control joints)

concrete will sink:
poorly compacted or inadequate sub-base
high water table eroding the sub-base (inadequate sub-base)
freeze / thaw damage. (inadequate sub-base)

sounds like you have a combination of the two..

No cement finisher worth his trade or with pride in his work places a slab that large without control joints.

my 45 X 25 has 1 control joint midway and then divided in 1/4s not one crack !

Anyone who says all concrete cracks is simply a lousy concrete contractor

 

[JACDes]

How about this?

This is only good if the ground beneath the slab is stable and not prone to frost heaving.

unless you know what is underneath you are taking a chance that it will fail after a major freeze / thaw season.

 

[lattimer17]

Replacing the slab is the best bet.

As stated before, the shifting of the slab is due to any of the following:

-water intrusion
-improper compaction of subbase
-improper protection from frost heave (likely not an issue in your area)
-improper protection from expansive soils (if you have them - don't know)

If you simply top the area with a self leveling compound of some sort, the cracks you see WILL translate through the topping. Whether or not the settling continues is up for debate, as it depends on the cause(s)....which we don't know.