Concrete shop floor repair/repour

[harryball]

The floor in the new shop has several cracks and a displaced segment of concrete. I've checked, it is stable. It looks like some of the damage was done when the concrete was still green. In addition to cracks, one corner is broken off about 6' back. The section drops about 2" over that distance and the crack is as much as 1" on top.

What have you guys used to repair floors?
Got ideas?

I'd like to avoid a repour and do large patches then paint over it. I'm not concerned if it shows through so long as it is stable and water doesn't run into the cracks. If I do have to repour I want to get it as thin as possible, not sure how thin that can be or with what kind of mix.

/RB

[bleeth]

At this stage of the game you may want to consider self level flooring mix. If you have some big pits fill them with Sakrete or whatever and then do the place with self levelling compound. The next thing I would do is put down wood!! 3/4" or 1" T&G plywood underlayment. Your legs will thank you for the rest of your life. You may not even need the levelling compound.

[Brady Watson]

Dude...Just caulk it :D

Unless you feel like breaking it all up, or being disappointed with patches, the only real way might be to pour over it. All concrete cracks. The "key" is to install key joints so that it has a place to break as the weather changes. I just did a 2400 SF pour like this with a key down the center and 2 on each side for 6 pads that move with the weather. They contract in the winter & expand tight again in the summer.

-B

[harryball]

Plywood over concrete sounds like it would be a nightmare. Has anyone done that? How? What about high humidity i.e. Georgia?

A repour is sounding more and more likely. Just have to see how thin I can get it.

/RB

[bleeth]

It's done all the time down here. You put in a vapor barrier between the wood and the concrete (plastic or tar). I am making the assumption that this is a closed Shop not susceptible to flooding or rain coming in. The wood floats just like the prefinished wood flooring they have been using for years now. The plywood underlayment uses exterior glue. Major screwing is not needed.

Brady: You mean expansion joints? The self levelling mix the flooring guys use doesn't need that. I've seen it used in huge areas under everything from VCT to really big match grain marble tile.

[meatbal80]

If you want to just patch the cracks and fill in the dropped off corner i would recomend Ardex SD-P. This is the patch that i use to float subfloors under any glue down hardwood floors that need it. It has a very hig compressive strength and will hold up very well i am sure. I add some milk (concrete primer / latex additive) in place of water and paint a coat on the concrete i am going to cover just before i start mixing the patch.

Keep in mind that this stuff sets up very quick and you will only have 10 or so minutes to work the patch. For any deep areas i would fill it to within 1/4 in of the finished height and leave the top very rough. Then the folllowing day go back a skim coat the area smooth.

At least out here in AZ you can only find this product at floor supply houses. It is worth every penny of the 35-40 dollars per 40 pound bag. I have never had a problem with this product in the past 6 years since i switched to using this.

[Brady Watson]

Brady: You mean expansion joints? The self levelling mix the flooring guys use doesn't need that. I've seen it used in huge areas under everything from VCT to really big match grain marble tile.

Yes - but they are staggered keystone-like metal dividers. My concrete guy insisted on them - and I agreed. The other building has cracks all over the place - no expansion joints :eek:

Now that Joel mentions it...my brother did his garage with something similar to level it out and eliminate cracks. If I remember correctly, it was something like 4" down to 5/8" to level up. It came out great...but he doesn't have industrial equipment sitting on it either.

It's probably best to consult a pro, rather than a bunch of woodworkers.

-B

[bleeth]

Joel: Ardex is one of the trade names I was trying to remember as I wrote my reply. You are right. All the actual craftsmen I know swear by it.
Rob: If you have a Shoreline distributor near you (I think you do) they carry it. Pretty easy to buy from them.

[Gary Campbell]

Rob...
Monolithic slab/footings on grade or floating slab inside walls? Concrete that has moved this much is not very likely to be "stable"

If the cracking has not involved the footings, repairing the floor is not overly difficult.

Acid clean existing.
Transit or Laser to find high spot
Mark corners and snap level lines 1/2" above highest spot
Remove swing doors
Raise garge doors and cut track bottoms 1/2" above lines
Install grounds thru openings to level lines
Coat with latex bonder
fill cracks over 1/4" with high strength patcher
lay open weave fiberglass mesh over cracks at least 12" wide
Pour with liteweight gypsum floor leveler or 7 sack grout from redimix company.
A few "touches" with a vibrator will level
Finish as required

If footings are involved, call concrete jackers to pump them up in order to save walls.

[myxpykalix]

If you are talking about small cracking this may not be applicable but where parts of foundations are cracking and sinking because the underlying dirt foundation is eroding I have seen where they drill a hole in the concrete and inject expandable foam that raises the concrete and inturn stabilizes the foundation underneath.

[Xray]

You might want to look into an epoxy repair.
I'm a union carpenter, but have been doing expxy floors with a buddy on the side for 20 years, I havce patched 100's of miles worth of cracks.
For patching cracks, we use a mixture of "Cab-O-Sil", which is a very fine, powdery substance, and 2 part epoxy [resin & hardener]. This stuff bonds to cement better than cement itself.
In lieu of Cab-O-Sil, which is a specialty product and tough to find in small quantities, you can use sand instead.
You'd want to prep the floor be removing any lose debris, perhaps busting some off with a chipping hammer as necessary, then using a diamond wheel grinder to "open up" the floor in the vicinity of the cracks. You mix the stuff up to the consistency that it pours, but just barely ,,, And those cracks will be sealed into eternity.
Once set up, the only way to remove it is with a jackhammer.

Not a whole lot of outfits that do epoxy, might want to try to track one down and get an estimate.
Should be free, and you might find it worth the while to just have them do the work. Should get a 3 to 5 year warranty on the repair ,,, But really, its not tough to do by yourself.