I am building a patio home (concrete slab) and they will soon be pouring the foundation. One concrete worker that I know suggested that they should use 8 gauge mesh vs. 10 gauge mesh. I don’t know much about concrete to know if that would be a good idea for the extra cost or not. Approx. 2400 sq. feet. Any help would be appreciated.
This is my first post with FineHomebuilding. Looks like a great place to get some answers.
Thanks.
Replies
Rewire does nothing but hold the cracks together. Use fiber to control the micro cracking and don't let the finishers add water to the mix. Use a plastcizer instead.
KK
Wire mesh is pretty much a waste of time. It has to be very precisely placed in the bottom one-third of the slab to do any good. If it's a typical 4" slab that accuracy is almost impossible.
Welded wire reinforcement can do a very good job of crack control if placed properly. The problem is that contractors, especially residential contractors rarely (never) control the placement. They will "pull it up as they go" which means it is likely just sitting on the bottom of the slab doing nothing.
I will correct Florida though, because to control cracking for slab-on-grade the wire needs to be in the upper 1/3" of the slab, not the bottom 1/3. (The Wire Reinforcement Institute says 2" below the slab surface or upper 1/3, whichever is closer to the surface)
Also 6X6 "10 ga" mesh, or 6X6 W1.4XW1.4 wire is pretty typical around here for commercial and residential 4" slab on grade and should perform ok as long as it is placed correctly. The additional material for the 10 ga will not help near as much as using chairs or bolsters to hold up the wire.
The mesh mentioned above is another good option for crack control, but again it must be done right. Forcing a contractor that is not familiar with fiber to use is can be a recipe for disaster.
As with all concrete work, good workmanship often makes more of a difference in performance than anything (reinforcement placement, curing, joint layout and timing, ect.)
One of the things often missed with welded wire placement is at your planned control joints. Along the control joint's line, you should cut every other 'perpendicular' welded wire. This reduces the mesh's strength right where you want the concrete to break. Of course, this takes some preplanning and creative marking and placement management/review.