Rebar chair spacing.

wedge40 · Aug 25, 2012

Getting stuff together for cement pour. 40'x56', 5" thick, 3/8" rebar on 1' spacing. How far apart can I space the chairs.

Wedge

Raspy · Aug 25, 2012

With 3/8" bar and the activity of them walking all over the bar as they pour, I'd say you need the chairs at about 2' max along the bar. If you want to be sure there will be no significant bending during the pour, you'll have to go closer.

If you have a grid with the bar on 1' centers, running both ways, put the chairs under just the lower bars and offset on each one, or staggered. I'd try it with the 2' OC layout, staggered, and step on it to see if you are satisfied.

wedge40 · Aug 25, 2012

Raspy said:
With 3/8" bar and the activity of them walking all over the bar as they pour, I'd say you need the chairs at about 2' max along the bar. If you want to be sure there will be no significant bending during the pour, you'll have to go closer.

If you have a grid with the bar on 1' centers, running both ways, put the chairs under just the lower bars and offset on each one, or staggered. I'd try it with the 2' OC layout, staggered, and step on it to see if you are satisfied.

Thanks John, that's exactly what I was looking for. I was afraid I was going to get some nebulous answer. I can purchase for 18" along one way and should have more then enough.

Wedge

davo727 · Sep 3, 2012

Ya dont use too many or the concrete flowing into the slab will just knock them out of position and float them away cause there is not enough weight on them to hold them in place.

crazyal · Sep 3, 2012

Have you bought the rebar yet? Two years ago when I built the slab for my garage it was cheaper to buy 1/2" than 3/8". I'm not sure if that's still the case now.

dave1949 · Sep 3, 2012

You could wire tie the chairs to the rebar, these work slick: Tying Tool for Rebar Tie Wire: Amazon.com: Kitchen & Dining
with these: A7031000 - Uponor (Wirsbo) A7031000 - Fixing Wire (1,000 per bundle)

I assume you will wire tie the rebar at many cross points anyways.

RxRatedZ71 · Sep 3, 2012

My contractor tied the chair with that very type of handle and ties. They worked decent however he put them on 2' OC and in some areas near the intersection points I noticed that the weight of the rebar was crushing the chairs. I went back in and had to add some more chairs in strategic spaces.

My guy was trying to skimp in places though. He didnt want to cut shorter pieces of rebar so he took several bent t-post that i had laying nearby and threw them in instead. Of course i didnt know about this until my wife told me AFTER the pour.

newbury · Sep 3, 2012

RxRatedZ71 said:
My guy was trying to skimp in places though. He didnt want to cut shorter pieces of rebar so he took several bent t-post that i had laying nearby and threw them in instead. Of course i didnt know about this until my wife told me AFTER the pour.

Don't you just love contractors that borrow your tools and supplies! I had a basement repair job and they borrowed my wheelbarrow, 1/2" Milwaukee 18v drill, and several metal chairs.

You should have done another pour and put the contractor in.

wedge40 · Sep 4, 2012

No haven't bought the rebar yet. 3/8" can only be found at Menards and IT IS cheaper then 1/2" I'm going order the pex and manifolds today. Hope to have the company I order from do a basic layout. Got a couple of places I need to work around. I want to have everything set and ready for a 2 post lift in the future.

Wedge.

Raspy · Sep 4, 2012

wedge,

Here are a few pix that might help you with your radiant layout. it's just common sense. I've found it counter productive when a PEX or manifold supplier tries to give or sell you a layout. A few basic rules to follow and a bit of thought will get you what you want. It's much better for you to design it, and understand it, than it is for an unexperienced guy to do a roll out design from his office, for you.

Figure out the number of loops you want and don't let the supplier tell you how many. In the pictures you'll see I ran 3/4" PEX on 12" centers over most of the area. You might want 1/2" tubing which is more common, I don't know.

Also, I used concrete dobies under my bar. They tie to the bar with tie wire that comes sticking out of them.