ray324•10d ago

Am I the only one who used the wrong kind of rebar chairs for years...

I was working on a 4-story parking garage in Austin last spring and kept having the rebar sink into the mud during the pour. My foreman came over, looked at my chairs, and just shook his head. Turns out I'd been using the little plastic ones that are meant for slabs on grade, not tall vertical walls. I had no idea the chairs needed to be rated for the weight of the rebar and the concrete pressure. He showed me these heavy-duty steel bar chairs with a wider base and suddenly everything stayed put. Now I'm wondering how many other simple things I've been doing wrong on commercial sites. Has anyone else accidentally used the wrong supports or ties and only figured it out after a bad pour?

2 comments

2 Comments

fiona_clark10d ago

Those plastic chairs are a nightmare on anything vertical, trust me. The worst part is you don't even realize they're failing until you walk by later and see the whole mat sunk three inches into the mud. One thing nobody talks about is how the wrong chairs mess up your clear cover and the fire rating on your bond beams. I watched a guy get flagged on a re-inspection because the inspector spotted crushed plastic pieces and made them jackhammer out a whole pour bay.

robert_hayes10d ago

I mean, I get the frustration, but is it really that common? I've used plastic chairs for years on all kinds of slabs and never had a mat sink like that. Sounds like a bad batch or maybe the ground wasn't compacted right to begin with.