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Community and Q&A

Rebar lapping and minimum concrete coverage

ztrain727 | Posted in General Questions on

A couple quick code questions regarding rebar in the footings.

Does the 40 bar lappong requirement apply to rebar making a 90 degree bend? i.e. would it be ok for two #4 rebars to lap 10 inches on either side of a corner? Or do they need 20″ lapping in a straight plane.

Second question: is the minimum concrete coverage for reinforcing steel in footings 3″ as per the irc? As in 3″+ rebar chairs are required?

Many thanks!

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  1. Expert Member
    Peter Engle | | #1

    Yes, the 40x lapping reqiurement applies in corners. Typically, the longitudinal rebar is run close to the corner with the perpendicular rebar coming from the other direction. Then, a bent corner rebar with 40x legs is laid alongside the two intersecting rebars and tied to it. Google "concrete footing corner reinforcement" for some very good graphics of how it's done.

    The 3" cover applies if the footing is cast in earth, as in a trench. If forms are used, only 2" cover is required. This is for side and top cover. Since the footing is cast on undisturbed soil, the 3" cover applies to the bottom, so yes, 3" chairs should be used.

  2. ztrain727 | | #2

    Thank you so much Peter! This was a huge help. Just wanted to report that these specs passed inspection no problem.

    A little something to consider is the height of the rebar when you are calculating the height of your grid. We were only using 3/8, but the top bars on the grid brought the height up high enough that when we added radiant pex, the clearance to the slab surface got tight. We used 1.5ā€ dobies (rebar chairs). If I were to do it again, Iā€™d use 1/2ā€ or 3/4ā€ which would put the rebar square in the bottom third of the slab.

    Anyway, thanks so much for the help. Happy to have the slab behind us!

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