Poured my shed slab last week and went with rebar for the first time

I went through the same debate last spring when I poured a 6m x 4m slab for the caravan pad. Had mesh left over from a patio job and just used that, but the thing that made the difference for me was cable tying the sheets togather and using the taller plastic chairs instead of the bricks I'd used the first time. First slab I ever did, the mesh ended up half buried because I stepped on a low spot and pushed a whole sheet down. Second time around it stayed put because everythign was tied into one big mat, so nothing coud slide around on its own.

I've basically given up on both for anything under about 10 square metres. Last two pours I did, a garden shed pad and a bin enclosure slab, I just used fibre mix from the batch plant and skipped steel altogether. Cost me barely anything extra per load compared to buying mesh sheets, and there was nothing to trip over or kick out of place while screeding. The shed pad has been down three winters now with no cracking beyond a hairline or two at the saw cuts I put in the next morning.

I know fibre doesn't do the same job as steel if the ground moves, so I wouldn't use it on a driveway over reactive clay. But for a slab sitting on decent compacted ground with proper joints, I reckon the sub-base prep matters more than what's floating around in the middle of the concrete.

The tying every intersection thing you mentioned is exactly why I stopped doing bar grids by hand. My old man and I spent a whole Saturday afternoon on a patio slab years ago and my back was wrecked. If you've got the bar sitting there anyway it makes sense, but buying new bar just to tie it up seems like paying extra for the privilege of sore fingers. For your driveway next year, look at the pre-fab bar mats some suppliers carry if you want the bar approach without the tying marathon.

Tied bar on my driveway about five years ago, spaced at 300 centres and tied every second intersection because my back gave up doing every one. Held its height the whole pour, no arguing with it. One thing I learned though, the steel doesn't stop cracking, it just holds whatever crack happens nice and tight. Where I put my saw cuts is what decided where the cracks actually went. So for the shed slab, don't skip the control joints just because you've got decent bar in there.

Interesting reading this as someone who's only ever done one small pad with mesh. I'm nowhere near confident enough to tie a whole bar grid yet, the tying alone sounds like a whole afternoon lost. One thing I'd want to know before trying it myself though, do you have to worry about the bars rusting if the concrete cover is thin anywhere? With mesh I never really thought about it since the sheets are factory made, but if I'm hand spacing bars on chairs I'd be paranoid about one corner sitting too close to the surface. Does your mate have a rule of thumb for how far off the edges and bottom to keep things?

Funny how the labour flips depending on what you're buying. When I priced it for my patio slab, the bar was actually cheaper per metre than mesh sheets, but only because I could grab 6m lengths and cut them myself. By the time you add the chairs and tie wire though, the savings pretty much evaporated. Still, I'd do bar again for anything you'll park a car on, mesh always felt a bit flimsy for that.