T Nation

Concerete Slab Replacement Question


#1


I know we got some contractors/engineers out there. My slab garage slab failed. I knew it was a problem when I bought the house and priced that in accordingly; I'm just getting around to dealing with it. I am pretty sure it failed because: (1) un compacted fill and no compacted rock under the slab; and (2) drainage issue allowed water to run between a hole in the dirt where the driveway meets the slab, around the footing and under the slab. There was about a 8-10 inch void under about half the slab where the dirt settled before I took the sledge to it. I don't have issues with the footing; the house is level; and there is no cracking or sticky doors anywhere in my house; I have a basement and there are no issues with the basement. I'm also independently fixing the drainage issues, which is a whole separate project.

The slab appears to be just floating separate from the footer. Can I just use the current footer as a form, fill the floor with compacted crushed rock and a vapor barrier and pour, or do I need some sort of form between the footer or the concrete driveway and the slab so that the slab floats only on the dirt? I was thinking it might need some sort of rubber between the slab and the footer to let it float and deal with shrinkage or expansion if any occurs.

I also want to do it right. Is rebar overkill? I've been reading you just want good concrete with fiber and maybe metal mesh and a good base. My biggest concern with rebar is, fuck me, getting it out if I ever need to again. Hammering out no-rebar concrete is a fucking pain in the ass, I can't image how bad it would be with re-bar running through the middle of it.

I plan on doing as much work as I can myself and only hire when I need to. I will likely hire help for the flat/finishing work when I am at that point but I'd like to get the prep work mostly done myself.


#2

Here’s where the water was getting in.


#3

Use fucking rebar, you pussy. By the time you have to fix the fuckup you’ll invariably cause, your kids will be old enough to do all the demo work themselves, while you direct them from the comfort of your lawn chair with an ice-cold Sierra Nevada in your hand.


#4

Disclaimer: I’ve done some half assed rod busting on footers, built a few retaining walls, poured a fair amount of concrete. However, I in no way consider myself an expert.

I’d say yes to rebar, rent a jackhammer and tamping tool. The water issue is troubling. How is the drainage in your surrounding yard?

Also if the concrete in your garage sucks. I would be careful when you get a concrete truck in there. It might damage any other concrete.


#5

[quote]Captnoblivious wrote:
Disclaimer: I’ve done some half assed rod busting on footers, built a few retaining walls, poured a fair amount of concrete. However, I in no way consider myself an expert.

I’d say yes to rebar, rent a jackhammer and tamping tool. The water issue is troubling. How is the drainage in your surrounding yard?

Also if the concrete in your garage sucks. I would be careful when you get a concrete truck in there. It might damage any other concrete. [/quote]

Yes, the water issue is troubling, but I’m also taking steps to remedy it. The whole street drains into my driveway and there is only one shitty little drain to deal with it that gets plugged with mud. I am going to increase the size of that drain and likely also either french drain or channel drain around the front of my house and route it to the back and into the drainage creek. I am also looking into a few separate retaining-wall options to divert water before it gets to the driveway.


#6

Wow, breaking up concrete sucks. I’m debating keeping the concrete and finding a use for it, like material for a lower retaining wall, or hauling it to a recycler


#7

I’ve got a little Deere with a backhoe so trenching is no big deal.


#8

I poured a few garages last year. You seem to have a good idea of what to do. The fiber or rebar is a good idea, there are also different mixes you can get of concrete, If I had a car in my garage I would opt for a better mix so it would last longer. I would put a form right at the beginning where the laneway meets the garage, obviously on the inside of the garage.

I would might also run a form through the center to separate the two sides, this way you can back the truck up and drop the cement in a wheel barrow and get on level on one side, ie set the form level and pour up to the form. Then once you have 3quarters of one side poured you can remove the middle form and pour up to the other side that you poured that should stay to grade. I would also have a legit finisher helping you with the pour to make it look nice.

Oh yeah I forgot to mention about the stone, you really want to pack it down well, I forget how much stone to crete is ideal for a garage, i would do a few inches of stone pack it and do at least 4 to 5 inches of cement


#9

Wrap the body in heavy plastic first.
Be sure to create a sub-slab to encase it in, then use a 2 ft depth rock and soil fill. Finish off with top slab.

It’ll be a lot of work, but it will keep you from going to jail.


#10

We know about your carpentry and tile skills. Now this. Quit telling people you’re an attorney. You’re a contractor.

You’re doing this wrong. Get some Crossfit people to pay you to let them haul the broken slab out of there.
Advertise it as a wheelbarrow relay event. Charge them $25 each. More if they want to swing a sledge hammer.


#11

[quote]Powerpuff wrote:

You’re doing this wrong. Get some Crossfit people to pay you to let them haul the broken slab out of there.
Advertise it as a wheelbarrow relay event. Charge them $25 each. More if they want to swing a sledge hammer. [/quote]

This is too funny. I actually considered trying this little ruse, but started thinking about liability issues. I was thinking $100 a pop for a “sledgehammer bookcamp.”


#12

[quote]jjackkrash wrote:

[quote]Powerpuff wrote:

You’re doing this wrong. Get some Crossfit people to pay you to let them haul the broken slab out of there.
Advertise it as a wheelbarrow relay event. Charge them $25 each. More if they want to swing a sledge hammer. [/quote]

This is too funny. I actually considered trying this little ruse, but started thinking about liability issues. I was thinking $100 a pop for a “sledgehammer bookcamp.” [/quote]

Dude. Just sign a waiver and you are all good.


#13

It has been a long time but working with concrete was one of the things that convinced me college would be a good idea.

Use either fiberglass or rebar not both.

Is it a corner where it washed out? If so it shouldn’t see a lot of weight.

If it is bearing the weight of a vehicle I would dig 16" down in the problem area and add 12" of crushed limestone. Dampen it and tamp it down with a vibratory compactor. Bring it up to grade with sand and tamp that. I believe they use a vapor barrier now but am not certain.

Get some friends together for the pour, you have to work fast and raking concrete is really hard work. You don’t need forms, your driveway and ratwall should provide that. Do you have all the tools like a floatboat and edger? Finish is not too particular, it should be a broomed finish so it is not slippery.

Lastly you can either trowel a seam down the middle or get a masonry blade for your circular saw to provide a relief crack.

As for the issue of water from the street, I had the same problem but it went into the neighboring lot and then into mine. After putting in 5K worth of drainage didn’t cure it I built a berm/ flowerbed separating my lot from the one next door. I did this by forming two lines of small boulders about three feet apart and backfilling with dirt between them.


#14

[quote]Testy1 wrote:
It has been a long time but working with concrete was one of the things that convinced me college would be a good idea.
[/quote]

Concrete sucks.

Thanks for the tips. I had a pro come last night for an for an estimate and he gave me a prep list similar to yours and gave me a bid just for the pour and finish that seemed pretty reasonable all things considered. He also said it looks like the first panel of the driveway has failed as well so I also get to deal with that. And the drainage. But he also said the foundation looks solid and no major issues yet and I should be good once I get the drainage resolved.