Garage concrete floor

11 Replies

Will anyone with direct experience cutting out, and re-pouring a badly cracked garage floor please comment on the success of the job. Was rebar attached to the remaining perimeter foundation prior to pouring? I dont want too replace the garage but would like to fix the floor.

Rental or flipping this property? If it's rental and it's not that bad I wouldn't touch a concrete garage floor. 

That's a fat zero ROI for a buy and hold investments. In some cases its cheaper to build new but I feel you on fixing it. We did same thing at my primary home but rebuilt most of the roof structure on a two car garage. We rewired it, got new doors installed, and will do vinyl siding on the cheap.

No experience doing it on a garage floor but have seen it done on another concrete slab. You don't need to attach the new slab to anything - it just floats in place. Around here most of the concrete guys just pour straight to the edge but we don't get anywhere near the kind of freeze/thaw and ground movement that you'd get in Illinois, so you might want to have expansion board around the perimeter.

You might want to post up some pictures. If you are just talking about non-structural surface cracking that looks like hell, I would either just epoxy the whole thing or you can float a concrete resurfacing over it. If this is major settling/shear cracking, then yes you'd have to repour if you want it to look good. And as @Jaron Walling mentioned, if it was a rental or a flip would make a big difference, as well as the price range. Technically you don't have to have a concrete pad at all in a garage, which sounds funny but I could show you houses in my area that just left the floor gravel. Looks like hell but it's not a necessity. 

@Mark Shelstad picture may help but otherwise the answer is "it depends". My garage on my house has a foundation below the frost line that is not connected to the floor. You could jack hammer out the floor and pour a new one without disrupting the structure. My parents garage has a floating slab and the structure is attached to that slab. You couldn't just remove the entire slab in that case without potential problems. In that case you would need to cut and leave some slab around the outside. You would want to drill holes into the slab side to attach rebar. Be careful if it is just on the slab, because the entire slab is needed to maintain structural integrity. Sometimes they just place concrete blocks on the slab, but it is really the same thing. 

Another option may be to patch and resurface the floor. My parents had this done with their front steps. They used a vinyl concrete mix with high adhesion. They make products specifically for garages. It will look like new and can be very durable. Just be sure to prep the surface and install it properly to avoid cracking later. You can fix the cracks before you skim coat. This would definitely be easier, faster and cheaper than pouring a whole new floor. I would hire a company that warranties their work for a period of time. That way if there are future issues, you can refer the buyer back to the company that did the work.

I’m in Los Angeles, so weather is generally mild with hot summers. No frost/winter issues.

I had a garage floor where 1/4 was tilting and sinking. Over 3 years, it developed a ½” crack. After a visual inspection, discovered that it was the floor and not the foundation.

Cut out the damaged floor area, with extra. Drilled into the existing floor that was ok, rebar with epoxy. Poured new concrete. Did not attach to the foundation/steam wall. If it is to sink again, hopefully mush less likely to impact the foundation.

@Joe Splitrock Thanks. Here the garage floors on detached garages are usually a monolithic pour with the outside 12-18" thickened so as to act like a foundation. My thought is to cut the center area, leaving the thickened portion (which is under the walls anyway), drill and insert rebar, then pour the new floor. The cracks are large and it looks like someone in the past skimmed the surface already.

@Mark Shelstad - Is there any chance you can inject the crack with epoxy and then do an epoxy coat over the slab to seal it.  That would likely be cheaper than taking out the entire slab.

Doweling into the existing foundation is likely the proper thing to do along with some bond breaker where it is concrete on concrete.  Also, typically there is wire mesh in slabs.

We replaced a portion of the garage floor that was badly cracked and not allowing the garage doors to properly close. We did not use rebar, just had it hammer-chiseled out and new flooring poured. We paid $2,600 in the Greater Boston area to remove about a 4' wide x 22' long section and have it repoured. We couldn't have sold the house at the price we were looking to sell for without having fixed it.

Originally posted by @Mark Shelstad :

@Joe Splitrock Thanks. Here the garage floors on detached garages are usually a monolithic pour with the outside 12-18" thickened so as to act like a foundation. My thought is to cut the center area, leaving the thickened portion (which is under the walls anyway), drill and insert rebar, then pour the new floor. The cracks are large and it looks like someone in the past skimmed the surface already.

 Got is, so in this case there is no foundation. It is floating above the frost line. The thicker concrete on the outside helps carry the weight, but really doesn't do much more. My concern is cutting into the slab could harm the structural integrity. Theoretically if the entire slab moves at the same time, it floats and it is fine. That is not how it works in the real world. Different parts move at different rates and you get cracks. My concern is if you replace the center, it may start moving differently than the outside. You may actually remove what is holding it together. You definitely want to join it with rebar.

Whether you repair or replace, it is unlikely the cracks will appear again for several years. That is why I was leaning towards repair. Less cost and end result may be the same. 

Another consideration is topology of the land and drainage. Is the site flat and are their drain gutters running water away from the garage?

You'll need to demo the old floor, of course...then drill and epoxy into the existing stem wall. Attach your new #3 rebar to these pieces correctly. There will be instructions for spacing and tying the rebar. Of course you will need a permit, and inspections. Even a 'special inspection' depending on where you are....