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I will be pouring a 16 I 24 concrete deck with the possibility of closing it in in the future. Is the use of fiber in the concrete sufficient or do I need rear and mesh? The footer will be poured at the same time as the deck and will be 12″ by 12″. The deck will be 5″ of concrete.
Any help?
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Hi Ken,
I don't know if you're in Florida or Alaska so I don't know your frost requirements.
I don't know if you're on sand, rock, clay or swamp so I can't comment on that part either.
I don't know what your final project entails so I don't know the anticipated loading on this slab so I can't comment on the structural needs either.
BTW, I don't encourage the use of fibre in concrete because too much is expected of it and if the concrete cracks it's more likely to be able to lift as well as separate.
Welded wire mesh is much better.
Gabe
*Ken:The purpose of "fiber mesh" is to prevent cosmetic surface problems like spalding etc. It does not do the same things as WWF or rebar.Where I live the soil below all slabs that are installed in habitable spaces must be poisoned for the purpose of termite prevention, and you must have a certificate from a pest contractor. The alternative is that the pest control folks can drill the slab and inject the chemicals, which is obviously not as desirable. You may want to check on this in your area. Also, if you think you may want to build on this slab later, keep in mind that the building inspector will not be able to inspect your footers (footers are normally inspected with no concrete in the hole) - and he will want to know what's down there. Where I live concrete for exterior use is not inspected - not sure what the deal is where you live.What is the frost depth in your area? You really need to check with some local sources so that you i know what's required in your local building jurisdiction.BTW - the type of slab you are talking about is called a monolithic pour or sometimes a turndown slab.PS: here's a suggestion: don't use the BT spell checker
*For the last seventeen years I have work for an indepent testing lab that deals with soil, concrete and asphalt. The product you mention is called fibermesh http://www.fibermesh.com. It purpose is to replace the wire mesh in concrete slab. majority of the time the wire mesh that is used is laying on the bottom of the slab because of the workers walking on it, so in real life it has no structal value. While the fiber is embedded at all angle in the mix.And yes people believe it does not work due to the sizes of the fiber compare to welded wire mesh. But there are hundreds to the cubic inch. i am a strong believe because of the track reacord and the saving of labor. It really does replace the used of welded wire mesh. More question checkout the fibermesh web page or the concrete network web page
*You are absolutely right about the wire most always ending up in the bottom of the slab - one exception is when chairs are used to hold the wire up. But it i still often ends getting walked on.That's an interesting web site. Here's a quote from the FAQ page:"Is fiber reinforcement as good as traditional reinforcement?Fibers and traditional reinforcement represent two different approaches to concrete reinforcement. Traditional reinforcement is utilized to hold concrete together after it cracks. Fiber reinforcement provides an internal network of reinforcement to protect concrete from cracking in the first place."Still, I have seen fibermesh concrete crack badly - due to uneven support of the slab, so proper compaction of any fill is still essential.
*In Commercial work,we routinely install slabs on grade without re-bar, WWM or concrete with fibre mesh. As Matt mentioned, soil preparation is the key to a good slab. On large areas, we use control joints to break the concrete where we want and not random cracking.I don't agree with the fibre mesh claims.Nothing replaces WWM in the average concrete application. Like all products, they are useless if not installed properly. Good installers, always lift the mesh as they are working.Chat later,Gabe
*Yup, the wire mesh gets trampled. Rebar on not less than 12" centers supported on dobies, and you have a fair chance of being able to walk between the bars.-- J.S.
*Slightly off the fiber topic. In an addition requiring a 36" deep foundation the engineer has listed 2 items. 1) He wants me to tie into the existing 8' foundation with some kind of anchor (I presume an 3/4" expanding Wedgit type) but the notes indicate that it is made so I can add 24" of threaded rod. Ever heard of these....brand name? 2) Also in the notes is: "Do not form footer" OK, So I dug the trench the width spec'd for the footer and to the depth required. Now about leveling it out. Thought about driving some stakes to the grade line on the sides of the trench, resting some 2X on the stakes and using a notched out chunk of plywood to screed off the concrete. Pull the 2x out and leave the stakes? Any better ideas? TIA Thor
*Thor,On number 2, we routinely pour footings without forms. We use a laser and screed as we pour out of the chute.You can do the same with a regular transit/level but it's a little slower.With regards to number 1 question, ask your engineer for a clarification or alternative. Normally tying into an existing foundation requires anchoring only to prevent shear or movement left to right not from pulling away. In that case all we do is drill into the existing a foot or so and insert rebars as tight as possible and leave them extended by 2 ft. or more.Gabe
*Gabe: Thanks for the info. Engineer is out of town for a week so...... I would consider the same method with the rebar but he revised the drawings on me and they definitely show a 3/4" anchor and spec a treaded rod. I remember only a portion of an earlier discussion with him that rebar needs 24" to (insert proper engineer word here) grab, bond or otherwise be held securely by concrete. So how do you like the laser? What type and size? Do you use it for other work. How does it hold up when dropped in the soup?Thor
*Hi Thor,I have 2 hilti lasers and we use them for site and concrete work.GabeNever dropped one in the soup, so I don't know. Would have a hard time doing without them.