Re-bar Required Up Out of Base? What'd You Do?

[Dino_Pizza]

A new Forum member building his oven asked a question on his thread

http://www.fornobravo.com/forum/f6/g...sas-13415.html

about his ovens base or slab. His was existing so he stacked his concrete blocks on it and is ready to fill his cells (probably every other cell with concrete and rebar) but he asked this question:

Is it REALLY necessary to have rebar sticking out of the slab (from the bottom) into the cells?

I looked at lots of forum pictures and I see many that don't have any. I assume it's always preferable in a new pour to poke in (usually 4, 1 in each corner) a length of rebar, like I did. But, if you didn't I assume it's ok, especially if you fill in half the cores (the cement will somewhat bond to the slab) and the weight of our ovens will never allow it to move.

I think it's fine; what do you think?

[Tscarborough]

Re: Re-bar Required Up Out of Base? What'd You Do?

It is usually easier for DIY'ers to pour the slab, layout the CMU, THEN drill in the rebar, rather than calculating where they need to be before the slab is poured. They miss it better than half the time on commercial construction anyway.

However, if the question is do you actually need to have a mechanical tie between the stand and the slab, then the answer will depend upon your area. Seismic regions should always have the tie, non-seismic it is not really needed, but it is a standard detail of this type of construction. In short, a tie at each corner certainly won't hurt and the effort and cost is minimal.

[GianniFocaccia]

Re: Re-bar Required Up Out of Base? What'd You Do?

Given that the FB plans do not call for our ovens to be structurally attached to the hearth, one would guess that the same principle would apply to the oven stand. Even without rebar, isn't a bond created (however minimal) between the core concrete and the slab below?

I live in a seismic region right next to the San Andreas Fault, and in fact had a mag 5.9 earthquake yesterday. Although our chandeliers swung pretty good for about three minutes, my oven stand (without vertical slab/core rebar) looks unfazed.

[Tscarborough]

Re: Re-bar Required Up Out of Base? What'd You Do?

This is my Internet Advice Philosophy.

There are Best Practices for most industries. That does not mean that every task of every project will adhere to Best Practices. The truth is that Best Practices get adapted, diluted, misunderstood, and incorrectly applied.

The Best Practice for Internet Advice, therefore is to always advise the most reliable and resistant to minor imperfections method, i.e. Best Practices.


For example, I am comfortable having used old bags of masonry and concrete mix to build my 3" thick slab with a total of 4-48"x3/8" rebars. The slab is not tied to the CMU, none of the CMU were grouted, there is no tie from the CMU to the hearth slab which is composed of 30"x30"x2" thick 20 year old roofing pads, etc.

Would I ever recommend any of that to anyone, even though I am 100% positive that in my situation the oven will outlast me and the house?

No, absolutely not, nor would I use those techniques when building something for anyone else.

[Dino_Pizza]

Re: Re-bar Required Up Out of Base? What'd You Do?

Well said Tscar.

This reminded me of a funny thing that happened earlier this year to my cousin in a certain, guard-gated community of multi-acre properties in my area:

My cousin built an excellent 6'x10' chicken house, 7' tall, totally framed, roofed, sheathed and painted with hinged doors and clever flip-open pockets for retrieving eggs. He's a high-end wood craftsman by trade and done this many times before.

The next door neighbor is remodeling his house so an inspector can easily see into cousins yard. He came over to ask him about the "structure" and if it's permitted. "What's there to permit, it's a chicken coup" (say it like this: "eets a tsicken coooop"...with a heavy Greek accent).

Inspector said "did you have the roof structurally engineered? What if it collapses?"

My cousin has no poker face. He glared at the inspector and said: "If the #%@#ing thing collapses, then I eat them" ("Ay eeeeet dem")

And believe me, he will.

[mklingles]

Re: Re-bar Required Up Out of Base? What'd You Do?

I thought really hard about not including the tie down between the slab and the stand, but in the end just did it because it wasn't that hard. Probably would have been fine without it. I agree completly with the "best practices" advice.

[Evets]

Re: Re-bar Required Up Out of Base? What'd You Do?

I did not. Call me crazy but I'm not the least bit concerned about it. I did fill every other core including a 40" length of 1/2" rebar in each.

[Neil2]

Re: Re-bar Required Up Out of Base? What'd You Do?

For a new slab, I would do it. The cost and effort is minimal. The upright rebar should be bent and tied to the slab reinforcing.

For an existing slab, I would not bother drilling and grouting in a pin.

[MetalHead]

Re: Re-bar Required Up Out of Base? What'd You Do?

I did not. I had the base 4 courses laid and I placed rebar and poured some of the cells to create "legs" inside my base.

I did tie the rebar in the slat on top to the rebar in the "legs" on the base.

http://www.fornobravo.com/forum/8/ov...html#post65761

[ralogan55]

Re: Re-bar Required Up Out of Base? What'd You Do?

I just finished pouring my foundation slab, block stand, and framing my hearth (about to pour). I live in So Cal so I'm very generous with the use of rebar - it's cheap insurance.

Alway tie rebar with wire, never use string.

I put the vertical rebar into the foundation when wet. It's not that hard to figure-out where your block openings will be and it's much better than trying to drill into hard concrete. I wasn't off any more than a couple of inches.

I also made sure my vertical rebar was long enough to extend into the hearth. I was then able to tie my hearth rebar into my vertical stand rebar. I also left 4"-6" open in my stand blocks so when I poured my hearth it would integrate into the stand. The cost of doing this isn't that much more and it's better to be safe than sorry, particularly in earthquake areas or soggy soil.

[SCChris]

Re: Re-bar Required Up Out of Base? What'd You Do?

I tied 1/2" rebar into the slab that ran high enough to include a 90 degree turn to tie the horizontal oven floor rebar to. The rebar didn't cost much and I figured that here in SoCal more unitized shear structure is better. When we're dealing with these ovens we're not talking about much height for the oven weight to differ in momentum relative to the base in an earthquake. This difference is what tears things apart. The stand walls have a minimum of 6" width and most often 8" and in most stands the blocks are woven to create the corners. If I do another I'll add rebar again it's cheap.

Chris

[Neil2]

Re: Re-bar Required Up Out of Base? What'd You Do?

After the "big one", you can cook pizza for the survivors.


You are right though, rebar is cheap. Maybe one of the cheapest components of the build