Any Concrete experts here?

[David Cramer]

My question...is the wire mesh worth the cost of being put down before the concrete is poured? I am hearing varying things.

I have heard it keeps it level but can still crack regardless because it doesn't help prevent that.

I have also heard that if should be about 1/2 way in the concrete but that most workers step on it and therefore it isn't really where it should be when everything is cured enough to walk/drive on.

And lastly I have heard that you don't need it in 4 inch concrete but the thicker stuff you do.

Anyone know what I should believe?

Thanks,

David

[Matt Meiser]

All three places that I talked to about doing my slab prefered fiber-mesh in the mix instead of wire. Probably less work for them but the reasoning given was that its stronger and you don't need to worry about it being properly placed--on the slab in the existing portion there's one place where its actually at the surface.

[Lee Bidwell]

Hi David,

I don't know if I'm an expert, but I did pour concrete with my dad for about 10 years. We always used the wire mesh in the slab, and footings also get steel rebar run in them. There may be an argument for skipping the wire in concrete with fiber run in it, but we would always use wire. Stepping on it and pushing it down can be a problem. A good crew will pull it up into the middle of the slab as they are raking ahead of the screed board. Concrete rakes have a little barb on the top specifically for this purpose. If you are hiring this out, the best thing you can do is be there to supervise, and don't be too shy to ask questions of the crew if you see something that doesn't look right.

Lee

[Lee Bidwell]

Another difference between my experience and Matt's may be soil conditions. Where I grew up in the MS delta we have a lot of delta gumbo, and where I live now in Jackson we have Yazoo clay, both of which are very expansive with moisture levels. For that reason, we may do things differently than in other parts of the country.

Lee

[Scott T Smith]

Hi David,

I don't know if I'm an expert, but I did pour concrete with my dad for about 10 years. We always used the wire mesh in the slab, and footings also get steel rebar run in them. There may be an argument for skipping the wire in concrete with fiber run in it, but we would always use wire. Stepping on it and pushing it down can be a problem. A good crew will pull it up into the middle of the slab as they are raking ahead of the screed board. Concrete rakes have a little barb on the top specifically for this purpose. If you are hiring this out, the best thing you can do is be there to supervise, and don't be too shy to ask questions of the crew if you see something that doesn't look right.

Lee

+1 on Lee's advice. My personal experience has been that the fiber mesh is not as good as wire or rebar. Wire placement depends upon slab thickness. In thick slabs, the reinforcement is orientated so that it provides resistance to tension in the slab (concrete is very strong in compression, and very weak in tension). Typically this is towards the bottom of the slab. Mesh can be installed on top of slab bolsters or chairs, and good crews will reach down and pull the mesh up.

For a 4" - 6" slab, you want the mesh somewhere between the middle to the bottom 1/4th of the slab. You also want a dry mix, preferably with a slump in the 3.5 - 4.5" range. Proper sub-grade prep and a low slump concrete mix will do more to prevent cracking than the wire, but it's wise to do both.

[Peter Stahl]

Concrete will crack no matter where or how you pour it's just a matter of how much. The wire will help keep it together though. Biggest enemy of concrete is water getting in then freezing. I've seen a new driveway get water under it and freeze and it lifted and cracked it. Like Scott said the less water you have to use when you pour it the better and more cement in the mix helps too. I'm no expert but I stay at a .....

[Larry Edgerton]

If a subcontractor tells me he doesn't need mesh because of the fiber, he just fired himself. Its an excuse to be lazy and not do the job the way it should be done. It does not work.

All concrete will crack, at least in any frost zone. The mesh keeps the cracks at the same level so they can not shift up and down. If you don't believe it will make a difference, tear some out. No mesh: easy! Mesh: Tough sledding!

[Dick Adair]

Dave, the biggest problem with concrete that I see is the lack of a GOOD foundation. Everyone tries to skimp on the base. Depending on your location, the frost line is very important. I'm in central PA and I wouldn't think of a sidewalk with less that 6" stone. I'm not a contractor, but my 1st priority is a good base. Just my humble opinion.

[John Christian]

I am a superintendent on concrete highrises. I have between highrises and bridges and one hydro project ordered placed and supervised 100's of thousands of meter's of concrete. Mesh is a waste of time and money. If a concrete slab needs reinforcing then use ten mil bars properly chaired at 12" e/w. Fibre is good but can be hard to finish. Very important to have a proper base material and it well compacted
I have fibre added to my pool deck and no cracks after ten years. but a light fuzz is still visible when i am in the pool, looking out at eye level.
Feels good to have an authoritative opinion here after a year of lurking and poaching knowledge and ideas

[Larry Edgerton]

I am a superintendent on concrete highrises. I have between highrises and bridges and one hydro project ordered placed and supervised 100's of thousands of meter's of concrete. Mesh is a waste of time and money. If a concrete slab needs reinforcing then use ten mil bars properly chaired at 12" e/w. Fibre is good but can be hard to finish. Very important to have a proper base material and it well compacted
I have fibre added to my pool deck and no cracks after ten years. but a light fuzz is still visible when i am in the pool, looking out at eye level.
Feels good to have an authoritative opinion here after a year of lurking and poaching knowledge and ideas

Bull. Maybe in California, but here where we get four foot of frost, fiber does not cut it. I don't care how many yards you have watched other people pour. Rebar is fine but overkill for a slab. Heavy mesh works just fine. My family has been in the concrete business for generations, and if it was cheaper and worked we would use it.

The OP does not say where he is from. If he is in Arizona, sure, go with fiber. If he is in Minnesota, I advise steel.

[David Warkentin]

My understanding. In Alabama code says that fiber isn't good enough. But we can use it when we pour in Mississippi. Dirt that moves alot gets rebar each way. And yes, definitely have your guy pull the wire up. I've heard lots of comments about the wire being there to hold the plastic down...

[Peter Stahl]

My understanding. In Alabama code says that fiber isn't good enough. But we can use it when we pour in Mississippi. Dirt that moves alot gets rebar each way. And yes, definitely have your guy pull the wire up. I've heard lots of comments about the wire being there to hold the plastic down...

If you don't pull the wire, don't bother to put it in. We used to use the rolls and the mats. Mats are easier to use and a little heavier than the stuff on the roll.

[David Cramer]

Thank you for all of the responses!!! Much appreciated.

Firstly I am from Southeast Michigan.

I have heard to use the wire mesh, an additional $500 for my job, and then not to because it's only going to be 4 inches thick.

I've heard to use nothing but rebar...and to use nothing but the concrete itself if it's the right mix and the ground is tamped properly.

Again, thanks for the input and unfortunately I am still bit unsure but will ponder the posts and see if I can come up with an average.

David

[David Cramer]

In addition, the guy most likely getting the job said that he's digging down 4 inches of soil, and then adding 4 inches of crushed stone and then tamping it down with a "heavy" tamper. I thought I better add that in case it helps someone to help me out better. I know over time it will crack somewhere, but I want to minimize it the best I can.

[Peter Stahl]

How much concrete are you pouring? I didn't a couple rolls of wire would cost that much. If you know how many square feet you have then divide it by 81 for 4" thick concrete to get the yardage.