# Slab rebar

| Posted in Green Building Techniques on

I am getting conflicting answers on a small house rebar schedule. Some contractors claim rebar is not needed, others say wire mesh if fine, others don’t think #4 bar is needed and said #3 is fine, etc.

I called out for #4 rebar at 12″ oc

Rebar costs = \$4.70 per 20′ stick (#4) (21×35 pad)
So on a 3 feet on center pad = 19 sticks or \$90
On a 1 foot on center pad = 56 sticks or \$263

That’s a \$173 difference, right?

Yet that one contractor said it will cost a “fortune” for the rebar at 1 foot on center. He wasn’t talking about the labor but about the rebar. How is \$260 vs \$90 a “fortune” ? Unless my math is off?!?!

I could lay rebar myself. It’s not rocket science.

Some of these contractor are so full of hot air, it’s unbelievable.

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### Replies

1. | | #1

Perhaps you should ask the contractor.

2. | | #2

Peter. You're building a small house. Are you sure you need rebar at all. Is there a code consideration that is driving your decision?

3. GBA Editor
| | #3

Peter,
The rebar schedule depends on the loads, which an engineer can help you with. Point loads and bearing walls affect the answer -- as well as the height of the building and the roof snow load.

The contractor's bid is entirely up to the contractor, and depend on many factors, including the cost of labor, the cost of materials, the cost of overhead, and how busy the contractor is. If you don't like the bids you have received from local contractors, you can do the work yourself, of course.

4. | | #4

In many slabs, the rebar is there just to limit the size of the cracks. But add too much and you will encourage cracks that don't follow the control joints (if any). If rebar isn't required, then I'd start with "where can I tolerate cracks and how big can they be".

5. | | #5

What does your structural engineer call for?

there are variables here, a slab isn't a slab so specifics matter, I.e. Is this a slab on grade surrounded by stem walls, or a slab with thickened edges that act as footings, etc. #4 @ 12 oc does seem excessive, that sort of reinforcing would be typical of a spread footing depending on size and loading.

Your cost outlined above doesn't account for labor, every joint has to be tied, probably still not that significant in the overall cost of a house but easily triple the material cost you came up with.

6. | | #6

Chris,

The slab is on engineered fill (4" compacted AB and 3" rigid foam). It is a floating slab that abuts the ICF stem wall. It does not tie into the house/stem walls.

I've laid & tied rebar before. Today they have things like this which helps speed & simplify the process up:
http://www.homedepot.com/p/Hercules-1-1-2-in-Rebar-Chair-50-Pack-911/204220120?cm_mmc=Shopping%7cTHD%7cG%7c0%7cG-BASE-PLA-D22-Concrete%7c&gclid=CPy7ptjKs88CFZJlfgodC9ELkQ&gclsrc=aw.ds

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