What does engineering say?

In order to better communicate,
What is your field of construction?

 

Engineering and code have little to do with each other. Engineering must follow code, but can go beyond code or make stuff up if code doesn't exist.

 

I've never looked at IRC requirements, but to me it would be insane not to place rebar in a slab.

 

Would that be in the ACI code book?

 

I was able to find a reference in the IRC section regarding concrete floors to ACI 332, if you review that reference you will see they refer slabs on ground to be non-structural and specifically state they can be unreinforced or reinforced to resist the effects of temperature or shrinkage. In ACI 332, 5.1.6.1 states rebar may be used in applications where the number of control joints is to be minimized.

The irc also states that for expansive soils, the standards would be set by the IBC, which would then trigger a number of other requirements including rebar for structural slabs.

It isnt straight forward at all

 

I'm looking in the IRC 2021 and can't find any requirement for rebar or welded wire mesh being placed in the flat work of a monolithic slab.

Rebar is required by code in footings and foundations while there is no code requirement for rebar in a slab.
An engineer may include rebar in a slab if the slab is for special use.

 

I'm a GC; over 50 years in business.

Soil engineering, compaction testing, and concrete specs enter into the equation.

I've never professionally allowed a 4" residential slab. Too often that equals 3.5" actual.
Full 5" plus minimal thickness with poured piers and bar.

For what it's worth:

Personal anecdote: I live on a twenty year old finished, sans expansion joint or cuts, pour with zero cracks.

When in question, build stronger, build better.

R506.1 requires a 3.5" minimum concrete slab.
Standard pour is 4".
Garages typically are 6".

 

On sand or clay, like around Houston, ALL the slabs were waffle style with grade beams/footings on a 10’x10’ grid pattern.
Many were also post tensioned.

if you’re planning on building your own house and you’re here looking for input in order to save a few dollars, by not putting in additional metal, that’s on you.

I’ve never seen someone pour a house slab without reinforcement in the slab part. It’s the same for driveways. We would always add 20 foot panels of hog wire in the concrete. Seems like common sense.

I did work on one project where they used fiber mesh instead of metal in the garage slab, since we do crawlspaces mostly. Talk about ugly when you can go into the garage and see little furry pieces of fiberglass sticking up. That was the one and only time I’ve seen anyone use fiber mash.

 

Im not. I wanted to know if anyone had a standard or reference for the building code. I realize people have done it their way forever. But i found it interesting and figured id put it out there. Ive built several houses in florida with no rebar in the slab but we did place wwm. I always believed it was in the code to do so but i was wrong

 

Many, mistakenly, believe structural codes are the "be all, end all" of the best
means and methods. They are only minimum established structural and functional standards.

It's okay to exceed them.

 

Many, mistakenly, believe structural codes are the "be all, end all" of the best
means and methods. They are only minimum established structural and functional standards.

It's okay to exceed them.

Im aware its ok to exceed them. But the code seems to specify damn near everything else. Have you seen the latest year’s section on brace wall lines? Its 50 pages of specs.

 

Im aware its ok to exceed them. But the code seems to specify damn near everything else. Have you seen the latest year’s section on brace wall lines? Its 50 pages of specs.

Hey! Don't complain about the sometimes complex confusion of some regs.

It's why we're in demand as interpreters bridging the gap between engineers, architects, inspectors, and the folk who only want a safe, functional, and nicely built structure.

I s'pect any Pro has nightmare stories to share.

All should keep a favorite Engineer or two on speed dial!

 

People build differently around the country.
There are no code requirements for how to reinforce a slab here, it's up to your designer (engineer or architect) to design a floor system for the intended loads. Residential and AG stuff around here does not require an engineer or architect to sign off on plans.

We must have pretty good soils compared to other parts of the nation because we rarely used rebar in slabs unless they were going to be heavily loaded. Offices, Residences, garages, driveways, light to medium duty warehouse floors, etc. were almost always just reinforced with wire mesh. Having said that, we always built a good base to pour on and followed ACI American Concrete Institute standards regarding joint spacing, joint details, reinforcement placement, etc.

 

There are many areas of the country with no code compliance restrictions or inspections.

If I build something, you can "bet your Bippy" there's at least one Engineering Stamp on the plans.

WAIT! I take that back! I've built a few 'outhouses' and trash containers without engineering!

 

So why are you so hung up on this one specific aspect? Let it go. Go pet your dog

 

I think the saying is “ you can bet your sweet bippy “.

 

I think the saying is “ you can bet your sweet bippy “.

HAHAHAHAHA!

YEAH ! What you said !

You really ought to have consulted a sanitation engineer in those cases...😆

I only built them. Others did the movements.

 

Used to work with a very knowledgeable engineer some years back and according to him there was no code requirement for a floor, you could have dirt.

 

I've built a few 'outhouses' and trash containers without engineering!

You really ought to have consulted a sanitation engineer in those cases...😆

 

So what about fiber infused concrete. Does it work to hold it together?

 

It holds it together until it breaks. Wire or rebar will keep it from heaving or settling. Once fiber is cracked, it acts like there is nothing there

 

So nearly worthless. Wonder if they ever tried it with something like stainless steel fibers as long as 3".

 

Graphene carbon fiber........with a dash of 5G

 

I was told the fiber helps with holding the cream of the concrete from popping off of the limestone.

 

Only time I would ever use fiber would be for a thin "topping slab" where wire would be problematic to install. Something like a thin, second floor deck that is getting covered by finish flooring.
Another bummer of fiber is you sometimes get a "fuzzy" surface which is hard to sweep clean with a broom.

 

You want to improve the base. With a layer of aggregates that cost a tiny fraction of concrete per unit.... and lowers grading hand labor....
vapor barrier quality?
Sub drainage tile, gravity powered. To prevent water caused failure.....

Test of as used concrete to insure minimum strength of crete.....
Curing coating or covered during first 28 days for max strength.....
Vermin control issues from Crack control. And sub grade material selection: mono sized fill to prevent rodent hives.
I use rebar ,even in zero steel crete, at all edges, and thicken them to reduce drive on ' bust outs'.
Simple equations guide the % of steel needed to crete that use the cost of steel's tensile strength vs concrete's compression strength cost.... very rarely is a steel free pour the ideal mix.