Yikes - Garage Slab Settling/Cracked

[dgdoc]

Moved some racks in the garage today and notice that my garage slab has cracked/settled. This is in the far corner, away from the house. The wall looks OK, so maybe it is a floating slab and there is settlement underneath.

You can see how the slab has now dropped (maybe 1/4"?), using the molding as a reference point. The corner is still in place and molding is still flush.

Any ideas on how serious this is?

Other than filling the crack with epoxy (or something better) is there anything I should do?

Thanks.

 

[PT Doc]

If that molding is about 3-4" tall then it looks like you have 3/4" drop is some places if not more.

It can be mud jacked and corrected.

 

[dgdoc]

If that molding is about 3-4" tall then it looks like you have 3/4" drop is some places if not more.

It can be mud jacked and corrected.

Thanks.

Here is another pic. Looks like about 3/8" drop at this point.

Would this indicate that I have a floating slab - i.e., one that is detached from the footers for the house? You can kind of see the edge of the slab in this picture -- and looks like the wood plates for the wall are not on the slab, but on the footers.

Know anyone that's tried mud-jacking? Rough estimate on how much would something like this would cost?

 

[Edger]

I reckon it is almost certainly due to water at some stage getting under the slab for a while. Check gutter downpipes and blocked drainage pipes, anywhere rain can seep in under the slab.

 

[Grumpy365]

My first thought is the corner raised, not the rest of the floor sunk, but I can definantly understand your concern.

 

[dgdoc]

I reckon it is almost certainly due to water at some stage getting under the slab for a while. Check gutter downpipes and blocked drainage pipes, anywhere rain can seep in under the slab.

I thought the same thing, but looks like there is no erosion around that part of the house. The only thing nearby the foundation is some landscaping that has become overgrown over the years I've lived here.

Could the roots of the landscaping be messing with slab? Could it cause a drop?

Been in the house for 26 years. My latest theory is this may have been caused by poor job originally provided a solid base for the slab. Yeah, shouldn't happen with age, but if problem was there from day one it might've just started to reveal itself over the years.

My first thought is the corner raised, not the rest of the floor sunk, but I can definantly understand your concern.

It sure looks that way doesn't it? The left wall is pretty consistent going from 3/8" in the corner to maybe 3/16" over a distance of 20 feet or so. The right wall has the same thing going on, and gets worse toward the corner. The molding is very close to touching the concrete slab on other walls.

Would you recommend mud-jacking for 3/8"?

 

[dcs Inc]

The corner hasn't raised, it's just in a bind and hasn't fell yet. (2 sides holding it up). As far a recommending mudjacking, it's up to you. If this is bothering you, go for it. I would look at surface water. Which way is it flowing?

The reason this has failed is the original installer of the concrete didn't compact the sub base. It settled and so did the concrete that it was supporting.

 

[dgdoc]

The corner hasn't raised, it's just in a bind and hasn't fell yet. (2 sides holding it up). As far a recommending mudjacking, it's up to you. If this is bothering you, go for it. I would look at surface water. Which way is it flowing?

The reason this has failed is the original installer of the concrete didn't compact the sub base. It settled and so did the concrete that it was supporting.

Good info. Thank you.

Think your spot on with this being a problem from the original installer of the concrete not compacting the sub base enough. Was OK for years, but live in the house long enough and these original flaws begin to show up.

Can you elaborate on the "surface water"? Not quite sure what this means. The grade of the yard slopes away from the the right side (in the pictures) pretty well. The left side doesn't slope as much, and is where there is a lot of landscaping.

 

[dcs Inc]

I don't remember if this was a garage? Anyway, most garages have a slope to a door or a drain. That was what I was speaking of. If this had an original slope. Did it change? Is the slope needed?

 

[dgdoc]

I don't remember if this was a garage? Anyway, most garages have a slope to a door or a drain. That was what I was speaking of. If this had an original slope. Did it change? Is the slope needed?

Yes - This is the garage in my home. Assume it has the normal slope to help water drain whenever you wash the garage floor (I think it's 1/8" per foot - does that sound right?).

Anyway, I've been here 26 years and haven't washed it yet. (Not proud of that).

I'm just wondering if it's worth drilling a bunch of holes into the slab to have it mud-jacked a total of 3/8".

Also, can I assume that my garage slab is a "floating" slab and not connected to the footers of the garage? In other words, the slab moves independently and is not attached to the structure/walls?

Thanks

 

[dcs Inc]

Yes, this is a floating slab and not connected to the footing system. It this isn't hindering anything I'd just leave it and not go the mud jack route. You could even knock that corner down so it doesn't show the drop so much and be done with it.

 

[Anglia Guy]

I think I would remove all the trim on those two walls near that corner. Then remove the small piece of cement in the corner that is higher than the rest of the floor. Fill it in flush with the rest of the floor. Finally, replace the trim and let it go like that. If you have a lot of water on the floor, I would keep the trim up away from having it touch the floor. That way it won't soak up any water and rot.

 

[dgdoc]

Yes, this is a floating slab and not connected to the footing system. It this isn't hindering anything I'd just leave it and not go the mud jack route. You could even knock that corner down so it doesn't show the drop so much and be done with it.

Thanks for the excellent feedback. I wasn't sure if the slab was "structural", connected to the footers, and would cause problems with the house. Appreciate the advice on mudjacking - especially where the amount to raise is minimal (i.e., 3/8"). The holes in the slab created by the mudjacking processes would probably be more visible than the settling.

I think I would remove all the trim on those two walls near that corner. Then remove the small piece of cement in the corner that is higher than the rest of the floor. Fill it in flush with the rest of the floor. Finally, replace the trim and let it go like that. If you have a lot of water on the floor, I would keep the trim up away from having it touch the floor. That way it won't soak up any water and rot.

Replacing the trim is a great idea - and would make the settling pretty much invisible. The slope of the garage is still good and I don't wash the floor very often.

Maybe I should put down some kind of flooring like Race Deck while I'm at.

Hopefully there won't be any more settling.

 

[BJR]

Not to scare you, but I recently went through this:
http://garagejournal.com/forum/showthread.php?p=3267953

What's weird to me about yours is A) it's not resting on the footer along the outside edges and B) the soil disturbance away from the house should have been less than, say, near the house (assuming a basement). I'd agree with mudjacking but a part of me thinks it's not done sinking.