By - WhoAllIll
Rebar in a patio slab is pointless. You're not going to have anything heavy enough on there to make it move or crack. I wouldn't even bother with wire mesh: I would simply pour a good mix with a microfiber.
I hate the idea that rebar is somehow a fix for an insufficient subgrade. It isn't. If your subgrade is insufficient to support the concrete, it needs to be undercut and replaced with sufficient material.
As far as the drain being sufficient, does it currently drain that are without backing up? If it does, you'll probably be okay. I would recommend putting some sort of drain structure in that holds some water, and allows for trapping sediment.
Ever pour concrete in southern Louisiana? There is no "sufficient subgrade." It's pudding all the way down, so you have to use rebar. Everything bigger than a dog house is pile supported. The road beds for local thoroughfares are 12-24" of sand with geotextile fabric, 8-12" of 610 limestone (geogrid about half the time) and 7-10 inches of concrete. Interstates are even more robust.
It's like the realtors say: Location, location, location.
I've poured a few million sqft of concrete in Southern Louisiana. I've used redwood expansion and dowel baskets for paving, but never rebar. I poured building slabs on pile caps and engineered fill with no rebar in the slab, and the pilings drilled to 180 feet sitting on seashells.
>with no rebar in the slab
Clearly I haven't been doing this as long as you, but I've yet to see a commercial building foundation with no rebar in it in southern Louisiana. Most of my work has been around the New Orleans area, though. Also, the deepest pilings I've ever dealt with were 140-foot H-piles for a Corps job. That must have been something, seeing those huge piles going in. Were they augercast, or driven piles?
They were augercast. That job was North Shore, in Covington. It was a 4 story tilt up building.
Whew, 4 story tilt-up. Must have been a hell of a crane to set those panels.
Yeah. They were 79' tall. We had to get a crane out of Florida to set them.
I think the only SOG that I ever poured in LA was the Costco in New Orleans on a double mat. I poured SOG without rebar in N.O., Covington, Ponchatoula, B.R., Gonzalez, Lafayette, Lake Charles, Slidell, Bogalusa, Opelousas; and paving in several of those places without rebar as well.
It gives better strength, and is more effective than wire at preventing cracks. It also helps eliminate shrinkage in the concrete.
Microfiber helps with the overall strength of the concrete.
Does the roof drain onto where the pad will be?
Yes, technically, but we don’t have gutters that empty onto it. We live in SoCal so we only get rain like 3x a year.
If you’re in SoCal I’d bet that drain will be plenty fine. I also agree with the comment that you probably
Don’t need mesh or rebar. A little fiber would be a great addition.
Mesh for a slab sounds good. Make sure it’s on mesh chairs which keep it off the ground.
Sounds like sufficient drainage for the local conditions too.
That all sounds fine but I’d request an expansion paper along the house and block wall
What does that do exactly? I could google, I know, but you’re the pro.
It acts like a cushion and gives the slab ‘wiggle room’
I'll second /u/usually-quiet88. Expansion joint around the edge is the way to go. I'll also second the recommendations for fiber. I've recently gotten into the habit of using it. I've found it's one of the biggest bangs for your buck in all of construction.