3

I am hiring a company to do some concrete work. We are going to have an 11' x 10' slab laid over what is basically bare sand. We live in southern California and the temps can get to 122 in the summer. But we never experience freezing cold temperatures. Just thought I should mention that.

The contractor said we don't need rebar or wire for our project. But I wanted to get some input here before we start. The concrete is a little patio area for sitting and will have a small bar height table and four chairs. There will be a firepit. It will get very light foot traffic but no cars at all.

Should we use reinforcement? I'm getting a lot of conflicting advice from my searches online.

Thanks.

Adrien
  • 691
  • 5
  • 16
  • 2
    What is your argument in favor of **not** reinforcing it? The cost is trivial .vs. the cost of the concrete. But you can only put it in place before the concrete is poured... – Ecnerwal Apr 05 '22 at 18:57
  • 1
    Right. I'm not in favor of not reinforcing it. I am in favor of doing so. But the contractor said it wasn't necessary. If I choose to add it I am going to have to run to Home Depot and buy it myself and hand it over to them so they can use it. I just wanted to know if it was considered overkill and a waste. – Adrien Apr 05 '22 at 19:02
  • How thick is the slab? – manassehkatz-Moving 2 Codidact Apr 05 '22 at 19:19
  • They put 2"x4" forms in place. – Adrien Apr 05 '22 at 19:20

1 Answers1

5

Frost heave is likely not your concern, but soil movement due to ground shifts, erosion, water flow, and perhaps sprawling root systems of surrounding trees or shrubs is.

Support under the slab can shift for many reasons, sometimes leaving sections of the slab to support its own weight. The static load and any additional (seismic) vibrations over time can cause minute cracks in the slab. These cracks can remain contained if the slab contains mesh.

Rebar is used for larger loads (e.g. driveways, foundation) or for securing the slab to existing structures (garage, piers etc...)

The cost and labour of laying mesh are negligible compared to the total cost of the slab, and although the risk of failure is small, the small amount of extra effort IMO outweighs the hassle and cost of possible rework, and the (often) years of unsightliness preceding such repair.

P2000
  • 15,457
  • 26
  • 49
  • 1
    plus 1 for your answer... agreed. while it may not be needed, it's so inexpensive that it's stupid not to do it. – George Anderson Apr 05 '22 at 20:15
  • Thanks for the answer. I just spoke with the foreman and after talking with him and watching some videos on youtube by concrete specialists they talk about metal wire expanding due to moisture which can lead to cracks. Our foreman said that due to the moisture and salt levels that metal expands and rusts over time. He said he didn't recommend it. So now I'm left on the fence on what to do. – Adrien Apr 05 '22 at 20:45
  • Mesh is fully embedded in concrete by placing it in the lower half of the depth to provide tension support, but still 1in from the bottom to ensure it has no water contact. No exposure allowed. Cut to size; lift while pouring. What salt? Winter use? BBQ? – P2000 Apr 05 '22 at 21:00
  • Actually, you can find videos on youtube of concrete failing due to rusted rebar inside that accumulates moisture. I suggest you take a look. They're easy to find. The rebar, over time, rusts and expands. We live in the desert. Arid climates have higher salt levels due to lack of rain washing them away. The higher salt levels negatively impact metal. – Adrien Apr 05 '22 at 22:29
  • @Adrien yes rust & moisture are a problem (see my earlier comment) that need to be managed, but I haven't heard of opting out of mesh because of it. If you have a reference, please share. – P2000 Apr 05 '22 at 23:28
  • I have personal witness to rebar failing, @Adrien. I was awakened at 7am every morning of my freshman year of college as workers started jackhammering away the concrete to replace rebar in my dorm. The rebar had rusted because of anti-freeze in the concrete when they built it. That does _NOT_ mean it shouldn't have been used in the first place. Also, your pour won't involve anti-freeze, the dorm was poured in the middle of an upper Midwest winter. – FreeMan Apr 06 '22 at 16:51