How to Save Money When Buying Rebar Welded Wire Mesh

For residential work (slab-on-grade foundations, garage slabs etc...) I usually call out a 4" or 6" thick slab reinforced with 6x6-W2.9xW2.9 WWM. However, after some recent reading I'm beginning to think that rebar slab reinf. may be better for a number of reasons. One of which is how do you actually get out on a mesh reinf. slab without stepping all over the mesh, bending it and pushing it to the bottom of the slab even it is supported by chairs or dobies?

Perhaps a better option would be #3 bars at 18" o/c or #4 bars at 24" o/c, at least workers can step around the bars.

A confused student is a good student.
Nathaniel P. Wilkerson, PE
I almost always spec rebar in residential slab on grade applications. #3 @ 12"oc meets the minimum temperature reinforcing requirement of 0.002 * Area for grade 60 bar. I also leave a note for wire mesh specs in my general notes so that when the contractor calls and requests a substitute there's already a basic spec for the product in the plans.

I prefer rebar for all of the reasons that you mentioned. Wire mesh just doesn't produce as nice of a finished product most of the time. But really, there's so much more to a good concrete slab than the reinforcing. W/C ratio, concrete strength, curing conditions, etc, all have a big impact on the final product... If I had to pay for it, 6x6 W1.4 WWM all day. It is pretty standard and produces a reasonable slab. Keep in mind, these things can be poured without any steel at all. The mesh just restrains cracks.

If I was building my dream home (and not paying for it), #3 bars @ 12" o.c. so that I know is will be in the right location and will actually do something. There is a good cost associated with this though.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller
The min. reinf. requirements for shrinkage and temp. (ACI318-11, Section 7.12.2.1) specify the following ratios for slabs:

.002 for GR40 or GR50
. for GR60

Also spacing should not be farther apart than five times slab thickness or 18 in. For a 6" slab the 18" requirement controls.

This section deals specifically with structural slabs. Are SOG applicable?

How does the WWM meet this requirement? For residential work it seems like we are constantly breaking all of the rules but no one seems to care.

For a 6" thick slab with GR60 bar per the ACI318 I get the following max. spacings:

#4 bar = 18.17 inches (18" controls)
#3 bar = 10.23 inches

For a 4" thick slab with GR60 bars I get the following max. spacings:

#4 bar = 27.26 inches (18" controls)
#3 bar = 15.33 inches



A confused student is a good student.
Nathaniel P. Wilkerson, PE
I don't think a 4" slab on grade in a residential unit is really considered "structural" and therefore it probably doesn't actually have any reinforcing requirements. Since a slab on grade is continuously supported by soil, the plain concrete chapter in ACI 318 could be referenced but again, if it's not structural then why use the "structural plain concrete" code. A quick check of the IRC didn't turn up any requirements but I rarely look at the IRC, so maybe there are requirements that I'm not aware of.

I know that ACI 302.1 has a lot of information about slab on grade design for various different performance requirements but I don't have a copy of it...

As far as putting a bar at 48" oc, why bother?

To your original question, I think rebar is more likely to provides a better end product than mesh but it's undoubtedly more expensive so one must balance the cost with the desired end product. I've been going pretty liberal for my residential slabs on grade.

Interior = 3.5" with no reinforcing. Really easy to walk through.
Garage = 4" with 10M@ (1/2 x 0.2%). That's easy to walk through and provides a bit more durability. Not sure if it's required.

SE's in my market are stodgy and going with an unreinforced slab on grade makes me look like a fool / ballsy maverick. Contractors eat it up. I use the un-conservative tack here in exchange for credibility that I spend elsewhere on issues that are more important to me. I usually have a chat with the client regarding expectations and the fact that they're not buying the main floor slab of the Guggenheim.

I don' believe that either the 0.2% or the 5X apply to slabs on grade. Slabs on grade are not generally reinforced as flexural members and the restraint condition for SOG is much different than it is for suspended slabs (it's worse actually).

Some related ACI info:





I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

Save time and money compared to standard rebar

Welded wire reinforcement (construction mesh) is an efficient and economical replacement for rebar as reinforcement in concrete construction. The use of welded wire reinforcement saves time and installation costs compared to standard rebar concrete reinforcement. Wires are welded into a sheet eliminating the time needed for tying rebar, and ensuring that the wires will not move when concrete is placed.

With competitive price and timely delivery, Heyou sincerely hope to be your supplier and partner.

All Tree Island Steel’s welded wire reinforcement is manufactured to strict industry standards and complies with ASTM A / AM. Galvanized coating options meet ASTM A641 / A641M standards.

If you want to learn more, please visit our website Rebar Welded Wire Mesh.

Further reading:
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Rust is OK! Studies by the Concrete Reinforcing Steel Institute (CRSI) have found that a moderate amount of rust does not affect the properties of the metal. In fact, tightly adhered rust on the reinforcing steel is not detrimental to bond, but rather can be beneficial. To learn more about the rust myth, click below.

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