Update on slab project and more questions

[Gary_in_Indiana]

I met with the concrete contractor this morning and showed him what I wanted done, etc., and am waiting to hear back from him tomorrow regarding the job.

A couple questions came up I wanted to share here and about which I can hopefully get some feedback. First let me tell you the things on which we're already in agreement. We're going with 4,000 pound test concrete six inches thick with reinforcing wire poured over a stone base applied after the top material (a mix of dirt, dust, sawdust, petrified manure and whatever else) is removed to a virgin base. The thickness of the base will be determined by how much top material has to be removed. The perimeter of the slab will have a 'rat wall' poured into a 6" wide by 6" deep trench around the edge of the pour.

Now for the questions. One had to do with the material used for the base. The contractor said he will, of course, use whatever I want but that he commonly uses recycled crushed concrete as a base. Any thoughts on this other than that it costs less money? Any pro's or con's besides that?

Another question had to do with a drain or drains. The slab is going to be 40' by either 40' or 48' depending on the dollars involved and I'm wondering whether I ought to have one drain or more than one and what size/style would be best. He said I'd be better off with one larger drain than two smaller ones. For no particular reason I've always liked the trough style with the slotted steel grate over it. What do you think on drains as to number, size and style? Also what about placement of the drains in the slab and, again, why?

Lastly, what comes into your mind that I haven't addressed here? Thanks. /forums/images/graemlins/smile.gif

 

[Deerlope]

What to heck are you going to park on a slab like that? The first and only thing that I can think of is the space shuttle or an M-1 Abrams tank (60 ton by the way for the tank).

 

[Egon]

Should be nothin wrong with recycled crushed concrete.

As for drains the open type with grate is very easy to unplug. How many and where is hard to answere as it's your garage and I'm suspecting it'll see something quite a bit larger and heavier than an ordinary P/U .

Egon

 

[RobS]

Gary, I've used recycled concrete extensively around our place. Our driveway is "paved" with it, I've used it as base under landscape blocks and most recently I used it to fill in under our yet-to-be-poured patio. It's cheap, free of compostable material and packs extremely well. For the driveway, I still find bits of metal (rebar/rewire) occasionally but for fill under a slab that wouldn't be a problem at all.

When I did our service drive out back I rented a compactor. After smoothing with my tractor/rake, I compacted it all. It was nearly as hard and smooth as poured concrete. Of course, it doesn't stay like that forever but it is pretty neat stuff /forums/images/graemlins/smile.gif

 

[Gary_in_Indiana]

I'm guessing from the comments about the Abrams tank and space shuttle that I might be guilty of my typical overkill here. Actually, the only things I'm likely to put on it are my tractor, my implements and maybe an F-450 dump/plow truck or maybe rarely a medium duty 34,000 pound service truck at the very most.

Am I overdoing this with a six inch slab in an old pole building last used as a stable and riding arena? I'd like a slab to last but this isn't likely to ever be more than storage and maybe a shop. Am I spending more than I need to here?

 

[beenthere]

If mine, it would have plastic under the concrete pad. This will keep moisture from coming up through the concrete, keeping it drier in the long run. Contractors don't like it because it holds water longer, thus takes longer to finish trowel. The last contractor I had put 1" of sand on top of the plastic, and it helped greatly on the time to finish trowel.

I put in trap drains that had a cover that could be removed for cleaning sand and dirt. They have worked real well, and there is one under each vehicle in my garage and the tractor in the shed. Melted snow is the main reason for the drain.

 

[bgott]

Floor drains in any slab that accommodates objects that could possibly leak oil might possibly create an EPA problem. I've worked in a couple of shops that filled the drains with concrete for this reason. I never found out exactly if it was a government agency or an insurance company that had them do it, it just was done.

 

[bczoom]

Gary,

I concur with all that the crushed concrete should be fine. If you don't use that, pea gravel would be best.

I too put in 6" crete (and about the same size). I went with the fiber reinforcing as opposed to the wire mesh. I've had no problems with it whatsoever and it's a lot cheaper (and easier to work with) then using the mesh.

I also installed the plastic vapor barrier below the crete like beenthere noted. My contractor actually recommended it.

For the floor drains, a couple factors come to mind.
I put in 4 trap drains and placed under where I thought vehicles would park. When the snow melts off, the water goes under the vehicle where you won't be walking on it.
If you're expecting a lot of dirt/crud, the trough style would be easier to clean.

Are you going with a broom or smooth finish? I went with a smooth finish. Easier to clean with a broom. For cleaning either type of finish, I found a leaf blower works very nicely for getting everything out.

For the oil leakage issue bgott brought up, having a smooth finish and nominal leakage (normally from the equipment just leaking), I just pull it up with a rag. If you're using this as a "shop" as opposed to a storage building or have extensive leakage, keep his thoughts in mind.

Another thing to consider is how the contractor will set up for expansion and cracking. Is he going to put expansion joint around the perimeter and at joints, saw it, use zip-strip or ???