Concrete slab advice

[spebby_92]

I am having a monolithic slab poured (25' x 30') with 16" (w) x

18" (d) footings. 18" is below the frost line in my area. This slab will also have a 6" (h) x 4 1/2" (w) curb along the outside edge. I am a little concerned about the quality of the work by the contractor. My questions: Should the curb have re-bar? If so, what size? There will be anchor bolts (j bolts) 4' o.c. along the curb. How should the re-bar (#4 (1/2')) be set in the footings? By that I mean how far below the surface should the top re-bar be? There are 4 lines of rebar in the footing, two near the bottom and two near the top. In my layman opinion, the top set is too close to the surface. Also, the re-bar is tied to a vertical length of rebar driven into the ground. Is this acceptable? Any comment will be appreciated.

[DanG]

Rebar exposed to dirt should have 3 inches of cover. Formed concrete should have 1 1/2" of cover. Most curbs do not have steel. They do have load transfer dowels at joints - these are 1" thick slick dowels about a foot long.

In commercial work, the 4 bars in the footing would typically have #3 cages (stirrups) at a particular spacing, usually 12" c-c. These beam reinforcements are usually hung in the forms, spaced away from form surfaces, and poured.

The Corps of Engineers and other architectural concrete agencies will not allow driving pins in the dirt to support reinforcement. The contention is that said rebar will rust and the rust will get into the rest of the reinforcement.

There are sure many installations on driven pins. I have dug up old work that has been in the ground for over 50 years where the rust had no gotten to the pins in the dirt, much less the grade beam steel. I have dug up old footings, etc where the cage steel was exposed to the dirt (was not spaced away and covered properly), the rebar had rust, but was very viable.

Your call. It's your stuff. If the fellas are making an honest effort at holding the steel to grade, providing temporary spacers to keep the steel away from the dirt, plan to use a vibrator, and can show other pours with a decent finish, I think I would leave them alone. These issues should have all been resolved before they ever started, to change now sounds like a recipe for disaster.

[spebby_92]

Thank you very much DanG for that response. I know very little about concrete work and thus don't know quality when I see it. Plumbing, electrical and roofing I know well enough to make sure I'm getting a quality job.

[John Loomis]

Hello, I am a Concrete Contractor and Builder in Calif. The footings should have re-bar in it spaced at least 3" clear of soil. The re-bar near the top of the footing can be 3" or more....... In a curb application, it is best to have the rebar in the curb since anchor bolts will be attached in the concrete and used. The re-bar will hold the curb together on the top of the slab. Usually contractors try to support the steel from tie wire and hanging the rebar from the top. concrete blocks can be placed on the bottom of the footing and rebar placed on those.(3" dobies) One can also bend rebar to support the upper bars in an L formation. It is tied to the bottom steel and sticking up high enough to support and tied to the upper steel. Diagrams for footings are easier to understand. Rebar is the best for concrete slabs, footings, etc. Neat work and tied neatly is best. 2' overlaps at splicing is best. (or 40 times the diameter is the right length for a splice.) 1/2" times 40 =

[spebby_92]

DanG, I have "fired" the contractor working on my slab and have opened the door for the "recipe for disaster." I really had no choice. They would show up without the tools they needed, for example, the day they came to set the forms they had no spool of string. I loaned them one. They would work an hour and then leave and I would have to call to get then back after a day or two. Today I called and they told me they were waiting on me, I was supposed to call and get the inspection. The last time they were on site they said they needed to go get a drill to set some dowels and it wasn't ready for inspection. They were on site about an hour that day. I haven't seen them since. The steel in place looks like a roller coaster, with portions higher than the finished slab. They talk a good game but could not produce. Nothing they said happened. This will probably wind up in court. I have banned then from the site and told them I would call when they could come get their steel and forms. With the footing dug, it will be difficult to set new forms. Hopefully, I can find a contractor willing to clean up the mess. Of course I;m looking at a delay of at least 4 weeks. I contacted the guy you recommended but he never returned my call.

[spebby_92]

Thanks John Loomis for your response, it was helpful,

[Ralph Hertle]

[text omitted]

Simpson StrongTie has a simple new anchor bolt that could work for the application.

The bolt rod is bent so the anchor piece below is located closer to the center of the grade beam, and the threaded rod top is located at the center of the narrower curb and extends vertically up thru the center of the possible [2x6] wood sill.

Ralph Hertle