# is re-bar required in patios



## stanleygrade (Mar 16, 2010)

My contractor, landscaping our property in San Francisco poured our patio without re-bar or wire mesh. He said it was not needed. Is this correct or is re-bar required in patios. 

thanks


----------



## jlhaslip (Dec 31, 2009)

Rebar serves the purpose of avoiding separation of the inevitable cracks which will appear on slabs.
I would use some in your patio. Or 6x6x6 wire mesh at minimum.


----------



## forresth (Feb 19, 2010)

it really annoys me to hear how some contractors cut corners like that. 

that mesh is dirt cheap, and while probably not required by code, is definately a good thing to have.


----------



## stadry (Jun 20, 2009)

your guy's absolutely right imhpo,,, rebar adds FLEXURAL strength & wire mesh ONLY ' works ' during the ' green ' stage to resist tension forces,,, after that, it holds the broken pcs of conc together :laughing: mesh MUST be placed at/near ( 5% ) of the slab's vertical mid-point to even work well,,, try making sure of that when having to trudge thru wet mud - don't work !

just replaced my OWN driveway 2yrs ago - NO mesh - NO rebar - NO fiber - 2,600sf,,, we DID, however, have in place the proper jnt pattern,,, no crks nor do we expect any.

most guys ( even pro's ) don't understand the advantage of steel in conc - eg, in patio/driveway/pool deck/bsmt floor, it NEVER adds compressive strength yet its necessary for columns & bdges !


----------



## forresth (Feb 19, 2010)

there is a big difference between concrete that cracks at the score marks and remain level vs. slabs that jut up into the air 3 inches, creating trip hazards. reinforcement would have saved me from needing a new sidewalk


----------



## stadry (Jun 20, 2009)

whoever ' scores ' conc & expects it to crack at the scoreline takes big chances,,, that's the primary reason we've developed ' green ' conc diamond blades,,, i don't expect the avg conc jabonie OR a h/o to know that, tho,,, look for another reason to explain the 3" - its not steel OR the lack of it,,, lemme suggest poorly prep'd base mtl OR non-granular base mtl as prime suspects follow'd by tree roots.


----------



## pitonspud (Mar 18, 2010)

*Yes*

I am a JIW and yes rebar is required. Concrete has axcellent compression strength and lacks tensile strength. This is where rebar comes in--rebar has excellent tensile strength. With out rebar the concrete will crack when it shifts as the soil shrinks and expands or shifts. If he thinks rebar is not required don't have him do the job as he probably would not install the rebar properly. 

Good luck


----------



## stadry (Jun 20, 2009)

ignorant as to defining ' JIW ' ( journeyman-in-waiting ? ? ? ) but do we really disagree ?,,, wire mesh does add tensile strength during the ' green ' stage as i stated,,, successful concrete work also requires a good understanding of base prep including soils mechanics,,, conc will more likely randomly crk from lack of proper joints ( timing & pattern ) than it will from steel/wire omission,,, conc expands when hot & contacts when cold - nothing to do w/soil shifts - soil & base prep ( incl vapor barrier ) is a separate issue address'd PRIOR to placing the mud.

'sides, the op stat'd the patio's IN - *ALREADY install'd*,,, he just wondered IF there shouldda been steel/wire mesh,,, still maintain his contractor was right !,,, therefore, subsequent posts are for the op's peace of mind, i'll bet :laughing:

have NO steel in MY OWN D/W - even at throat - no crks, either, after 3 yrs ( its been longer than i thought :whistling2: ),, placing wire mesh is a critical measurement,,, aci sez it goes at the vert midpoint of the slab +/- 5%,,, in a 4" slab, that's 2" +/- .10",,, in all the yrs of placing conc, ain't yet seen any jabonies who'd tramp all over & thru the mud who could do that NOR any observant engineer who ever measured - they know what's going on, too ! 

ps - i don't use fiber, either


----------



## MI-Roger (Aug 8, 2009)

*Steel in concrete is just a future head-ache*

I never specify steel in concrete, other than dowel bars at load transfer joints. Reinforcing steel is almost never installed correctly, costs more money, and provides no benefit due to its inevitable incorrect palcement.

If the steel is uncoated, it will rust and corrode due to the wet and alkaline environment. Rusting steel expands, causing the concrete to crack, leading to more water infiltration, leading to faster rusting, leading to more expansion, leading to wider cracks....

If the steel is epoxy coated, it never bonds to the concrete and doesn't do anything.

Leave the steel out and make the slabs an inch thicker. Breaking out a failed slab containing steel is an expensive nightmare.

Proper control joint spacing and sealing (before the joints crack all the way thru and allow rain water or snow melt into the base material) is where the emphasis should be placed.


----------



## Big N8 (Oct 28, 2009)

I agree with this^^^^^^^


----------



## Termite (Apr 13, 2008)

Back to the original question, no it is not unusual for patio slabs to be placed without reinforcement. The code makes no requirement for reinforcement in basements, patios, sidewalks or driveways. Some enforcement jurisdictions require it, and the merits of reinforcement could be argued until the cows come home. 

Personally, I'd want it in my slab. It can be argued that it doesn't do much, but it would be hard to make a case for it hurting anything by being there. But your contractor isn't lying to you unless it is a local requirement.


----------



## pitonspud (Mar 18, 2010)

i disagree and agree. I agree that ground prep is critical and I disagree that rebar is not required. Where I live there is a high content of clay in the soil and ground prep back in the day in residential areas is not what it is now. In fact when this house was built in 72 there were no codes for ground prep. Slab and foundation issues are a big problem here. We are in what some soil/grading experts are calling a nine year drought. My neighbor had his driveway replaced and his house is ten years younger. His old driveway (not as old as mine) had no mesh and no rabar. And it had serious slumps, and cracks as wide as 2 inches in it; and yes there were joints. His new driveway had new base material and good ground prep done before they put rebar in it. And they actualy did the rebar properly. Drive down my block and you can tell what driveways don't have rebar in them. My driveway is 30 years old and trust me it has moved, in some places there is a four inch change in elevation---soils shift my freind. Many forces act on the ground such as vibration, shrinking, and expansion. Sweet thing about my driveway is that it has 10M running through it. The cracks that did occur did not spread open or create high lows as the rebar is holding it together and distributing those tension forces. The climate I live in gets as cold -45 C (no wind chill) in the winter and as warm as 35 C in the summer. So with these weather extremes doing the job right the first time is critical to the longevity of the structure in question. And placing rebar is critical in concrete. One person noted that proper placement of rebar is important--absolutley. Edge distance and proper bonding has to be adhered too. The fact remains that concrete has very poor ability to transfer tension forces. Concrete and rebar expand and contract at (virtualy) the same rate so they move together as forces act upon the structure. It can be argued that rebar does a lot.


----------



## Termite (Apr 13, 2008)

pitonspud said:


> ...and I disagree that rebar is not required.


I'm in full agreement with most of your statement, but...

Perhaps it would be better to say it is _needed_ as opposed to _required_, because as stated, code does not require it. Local requirements and amendments to code may however.


----------



## pitonspud (Mar 18, 2010)

thekctermite said:


> I'm in full agreement with most of your statement, but...
> 
> Perhaps it would be better to say it is _needed_ as opposed to _required_, because as stated, code does not require it. Local requirements and amendments to code may however.


Yes, the more I move around and boom out the more I learn that what is common in one place is not at all common in another. Geography plays an important role in building practices and how codes are developed. Codes seem to change as issues reveal themselves overtime, too. I can imagine that in some places the climate is very stable and applications such as a patio would not need rebar. I am very impressed to here about the driveway being 3 years old and not having rod in it--you should see the driveways that were built here last year by fly by night comapnies. They were falling apart after the first winter. Damn shame. My neighbor spent 25 000 on his single driveway that widens to a double garage at the back. Its about 80 feet long in total. I was impressed by the craftsmenship that the builder put into it and it still looks good and hopefully lasts at least 50 years..


----------



## stadry (Jun 20, 2009)

any jabonie can place & finish conc & some of them even get away w/it for yrs w/o knowing what in hell they're doing,,, unfortunately, they do seem to set the standard.

quoted a carport repair the other day replacing the front half ( 10'x20') & also the adjoining 1st slab,,, we waterproof'd her bsmt & never a drop since :thumbsup: told her i'd be high but it would NEVER randomly crack,,, her other quote's 20% below mine & he's using ' commercial ' concrete ( whatever in hell THAT is ! ) :laughing: bet you $100 it'll be crk'd all to hell w/i 1yr 'cause they won't jnt it properly,,, the soils under THIS particular slab ARE expansive - hence we did include steel ( & expansion jnt, of course )

my d/w has no steel - next door n,bor has his d/w crossing the original bldr's on-site trash dump,,, yup, big crater & dropp'd slab,,, we replaced that section w/DBLE-mat #6 & 8" slab - 750# flexural strength,,, its actually an at-grade bdge crossing :yes: point of all this is - you have to bld according to code ( min standards as 'mite sez ) yet you also have to design/bld to site conditions.

THAT is why/how jabonies stay in biz,,, h/o's don't know the difference but they/we DO understand $$$$$$$$,,, ain't nobody can fit 5gal of wtr into a 4gal bkt yet we generally get what we pay for !


----------



## pitonspud (Mar 18, 2010)

Hey itsreallyconc: Nice web site :thumbsup:


----------



## stadry (Jun 20, 2009)

hope it was some help understanding what's going on !


----------



## Daniel Holzman (Mar 10, 2009)

The subject of rebar in slabs has been discussed repeatedly on this site, I won't repeat history here. Those who believe that steel reinforcing is important in thin slabs (less than 6 inches thick) should consider that ACI code requires a minimum of 2 inches clear from any surface contacting soil, and 1-1/2 inches clear from any other concrete surface. This means that in a 4 inch slab, the steel needs to be essentially at the center, which is the neutral axis of the slab. This means that the steel performs no work, is under no stress, and the only thing it does is help to hold the concrete together if the concrete cracks due to improper base preparation, poor placement of the concrete, inferior curing practices, or failure to install control joints. Properly placed concrete, properly cured, installed over an adequate base, does not need any steel reinforcing.

As previously noted, normal steel reinforcing with minimal clearance (clearance is minimal by definition in a 4 inch slab) will eventually rust, expand and cause damage to the slab. In my opinion, steel in thin slabs is a negative, not a positive.


----------



## stadry (Jun 20, 2009)

isn't that danny a sweettalker ? ? ? :thumbsup: thanks for watchin' my back, bud !


----------



## mjmpdx (May 4, 2010)

*Rebar is not (necessarily) required*

The purpose for rebar for slabs on grade is for crack control. If the slab is properly jointed then the shrinkage cracks should occur at the designated locations. The PCA recommends that joints be spaced at no more than twice the thickness of the slab in feet. In other words if the slab is 5-inches thick then the joints should be no more than 10-feet apart. Furthermore the length/width ratio should be no more than 1.25 to 1. So, for example if your joints are 10-feet apart in one direction they should be no less than 8-feet in the other direction. So if the slab is properly jointed rebar is not necessary. However, it is pretty cheap insurance for two things: 1) if the slab does crack (unlikely if jointed properly) the steel will keep the crack "tight" (this is essentially what is happening with continuously reinforced concrete pavements) and 2) if there are weather extremes that would cause significant expansion the steel will prevent the slab from moving and causing the joint to "open up." Both are unlikely if the slab was jointed properly and you live in San Francisco, so I wouldn't worry too much about not having any rebar in it


----------



## stadry (Jun 20, 2009)

we're beatin' this thread to death, aren't we ? ? ?


----------

