Garage Build Continues

[1636Patriot]

Hello All, We have poured the footing on the 40x60 garage.. next will be frost walls with the anchor bolts in it...then the floor filled up to top of wall....I got a quote for a 4000psi with 6 gauge wire mesh in it...I'm thinking that should be good to put a lift anywhere. 2 and 4 post...Any thoughts?

 

[LopezBart]

How thick will the slab be?

 

[1636Patriot]

Sorry, 6 inch for entire slab

 

[billconner]

If you slab is "inside" stel walls, I assume you see top of stem all at edges when all is done? Just trying to picture that detail.

 

[1636Patriot]

Pouring floor flush to top of stem/frost wall...will only have 6 inches of foundation exposed where there are no doors

 

[wssix99]

Mesh and rebar are not required for slabs on grade. Adding steel to the concrete gives you extra assurance that you will NOT have cracking outside your saw cut joints.

If you want a quality slab, your saw cut joints are the most important thing:
- They should be spaced 10-12'-ish and be cut within 24 hours of the pour/placement
- They should be 1/4 the depth of the slab (That's 1 1/2" for your slab!!!)
- You'll want them straight...
- If you are going to put in a 2 post lift some day, you will want extra cuts so the fall in the center of your bay and and away from where your posts will go. (Cracks form in the saw cut joints and you won't be able to put the posts any where near these.)

^ If you do not discuss and plan these things with your contractor, they will not happen. If you do not watch your contractor like a hawk during the placement and during the cuts, there is a good chance you could get screwed. You'll want to be there to make sure you get your full 6" inches and all of the above happens.

Even 'nice' contractors will make mistakes here. They often send their most junior labor back the next day to cut your saw joints without adequate supervision. Any mistakes will become your problem. (in one way or another...)


(4 posts lifts are not as particular)

 

[ConCretin]

Most lift manufacturers require a minimum slab thickness of 4+ inches and 3000 psi so you should be fine there but it wouldn't hurt to check the specs of a few brands you are considering.

Control joints prevent ugly random shrinkage cracks you can see by hiding them in the bottom of straight, orderly cuts where you can't. Since lift posts can't be bolted down within a certain distance to a control joint (or crack), they will limit potential lift locations so plan carefully.

You could forego control joints entirely but in a 40x60 slab, shrinkage cracks are pretty likely and if you're unlucky, a random crack could prevent you from putting your lift where you want it.

As mentioned previously, the wire mesh you are installing doesn't do anything to prevent cracks, it simply holds them together after they occur. If you install the wire properly it will keep cracks tight and flush, which is especially important if you don't cut control joints.

Give my Guide to Floor Slabs in the link below for some additional thoughts on placing a slab.