Concrete floor - should I DIY?

[JLee]

I bought a house this summer with a detached garage in which I planned on installing a 2 post lift.  The seller called the guy who built the garage (who has since retired) and was told that the slab was 4.5" of mesh-reinforced concrete.  The blueprints for the structure showed 5" concrete.

I drilled holes for one post and measured at 4"...which is not great, but it's the minimum spec for the lift so it's ok.  I drilled holes for the second post and measured them at 3", so whoever poured the slab fucked it up badly and went 40% shy on concrete....which is not usable for me.

I can spend $6k to redo the entire slab (which I do not want to do), about $1100 to pay a random Craigslist concrete guy to come out and cut / replace a 4x4 section, or I can do it myself. Given that I have some small cracks across the slab, I'm considering cutting out and redoing a section about 4ft by 14ft (encapsulating both lift posts into the same chunk of new concrete).  I've mixed concrete before but never tried to put a proper floor finish on...I'm confident in my ability to cut / break up / remove a chunk of the floor, to dig out the gravel, put new gravel in and compact it, and to mix new concrete -- but I have no idea if I'll be able to put a proper floor-grade smooth finish on top of it.  Any thoughts from people who've done this before?

[Sibley]

Haven't poured concrete, but what about the potential for expansion between the old and new? Especially if there's a possibility you could get water involved?

And if you're already getting cracks, what does that mean for the overall slab?

[Fishindude]

Unless you want a real crummy job, get some experienced help for this.
4' x 14' x 5" thick is 0.85 CY of concrete.   You do not want to hand mix this, that will require approx. 69 bags of Sakcrete.

How big is the entire floor if you were to replace it all?   This would be my first choice for a first rate job.
Another option would to be to saw out and pour some beefy footing pads under each of the lift post pillars.

[JLee]

Unless you want a real crummy job, get some experienced help for this.
4' x 14' x 5" thick is 0.85 CY of concrete.   You do not want to hand mix this, that will require approx. 69 bags of Sakcrete.

How big is the entire floor if you were to replace it all?   This would be my first choice for a first rate job.
Another option would to be to saw out and pour some beefy footing pads under each of the lift post pillars.

Approx 21x25, quoted $6k to replace.

Haven't poured concrete, but what about the potential for expansion between the old and new? Especially if there's a possibility you could get water involved?

And if you're already getting cracks, what does that mean for the overall slab?

They're very thin cracks, but I don't think the overall slab was done properly, hence my thought of redoing the entire section that the lift is going to be bolted into.

I don't want to spend $6k redoing the whole thing...but if that is the only reasonable solution, I'll have to do it eventually.

[Papa bear]

I tore out my driveway apron by hand, had family that was in the business finish it, and used his company’s pricing on concrete. 

I spent 8–10 hours on a jackhammer, had to rent a dump trailer, paid one of my labor guys a half day to help out and haul away with his truck, and then called in a favor to family to do the pour at 7am for the finishing.

AND I didn’t really save much over the quote I originally got from a contractor, and I did everything right with the prep, got a good mix of concrete, got a really nice broom finish and sidewalk edge all the way around, and put on a fancy sealer while it cured.  Still had it spall after the first winter.

Point of this? I probably will pay someone the next time.  And there wouldn’t be a chance in hell that I would have mixed this by hand.  4 yards of concrete would have been crazy stupid to do.  And in your case, 1 yard would be crazy. 

So, either pay to have it done, or see if they’ll  let you work alongside, or just saw cut out for where your lift is and pour a footer.   


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[JLee]

I asked on NextDoor and found someone who had their 2 car garage floor removed / replaced for $4200.  My last quote was $6000, so I may give them a call.  At $4k I'd consider just doing the whole thing and being done with it forever.

[Jon Bon]

Honestly both of those prices sound good.

Concrete is expensive. and a small delicate job like yours lots of guys are not going to want to bother with. I have about 10 bids for my garage and I got maybe bids from 1/3 of them. The rest just ghosted me.

DIY a footer would work, but would look like crap. And if your the type of guy with a lift such things would annoy you most likely (they would me)

Just pay the man or deal with the cracked concrete.

[lthenderson]

I spent about $5k to have my garage floor torn up with a bobcat and repoured. It was the best money I ever spent since I spend a lot of time out there working on that concrete.

[JLee]

Honestly both of those prices sound good.

Concrete is expensive. and a small delicate job like yours lots of guys are not going to want to bother with. I have about 10 bids for my garage and I got maybe bids from 1/3 of them. The rest just ghosted me.

DIY a footer would work, but would look like crap. And if your the type of guy with a lift such things would annoy you most likely (they would me)

Just pay the man or deal with the cracked concrete.

Dealing with the cracked concrete isn't the problem - it's the fact that I can't install my lift because the slab is only 3" thick.

[JLee]

Turns out I have a friend who used to do concrete work -- he's offered to help :D