[BertS]

I would suggest

A. Hire a concrete truck...(even 2.5-3 yards, is alot of mixing).....us two sets of wheelbarrows (preferably the two wheel type), if the truck can't make it to the back yard (you'd be surprised, what they can do, or how close they can get with their chutes).....they will also do the math for you......

B. Get about 1/4 to 1/2 more yards, than what you think you'll need.

C. If you are tieing into an existing slab, be sure to dowel in, using slick bar. Every 12 - 18 inches, depending on usage of new slab.

D. Plan for early morning. Concrete works sux, and is tough.

E. Save the adult beverages, until AFTER the work is completed.

F. Be sure the forms are level and square.

G. If the slab isn't gonna have anything load bearing, which only 3" with a 4" thickened beam doesn't sound like it, use the mesh reinforcement.

F. Be sure to pull the mesh up, to get concrete between it and the dirt below.

G. Rent a vibrator.......it will help spread the concrete more uniformly..settle out the air bubbles, and help to make the new slab stronger.

H. Relief cuts, or expansion joints, to help prevent cracking.

 

[BertS]

oops.....

sorry, I didn't see the part about pouring on top of the existing slab?!?

hmm.......I'm sure it would save you some excavation, but I'd agree, probably not a good idea. There may be some serious settling of the existing slab, due to the added weight of new concrete on top. Unless there is some drainage problems, I'd shy away from that.

If you're set on doing that.....jeez......um, I guess you could chip some holes in the existing slab, use a post hole digger, to give you some piers to help support the weight of the new concrete???

That would seem like a lot more work, than excavating, to get the same elevation as the existing slab.

 

[BertS]

grade beams may be a bit of over-kill, and add additional cost, for a patio slab, as will the rebar? I do agree with getting the mesh in sheets, versus the rolls. I would also very seriously reconsider pouring new concrete over an existing patio slab. I'm sure, that when this slab was poured, that there weren't any beams, and mesh waus probably used. Be sure, that on any bars into your existing slab, either be slick, or sleeved.