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  1. #1
    Join Date
    Sep 2008
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    Default holes bored into beams

    R802.7.1 Sawn lumber. Notches in solid lumber joists, rafters and beams shall not exceed one-sixth of the depth of the member, shall not be longer than one-third of the depth of the member and shall not be located in the middle one-third of the span. Notches at the ends of the member shall not exceed one-fourth the depth of the member. The tension side of members 4 inches (102 mm) or greater in nominal thickness shall not be notched except at the ends of the members. The diameter of the holes bored or cut into members shall not exceed one-third the depth of the member.
    Holes shall not be closer than 2 inches (51mm) to the top or bottom of the member, or to any other hole located in the member. Where the member is also notched, the hole shall not be closer than inches (51 mm) to the notch.

    Here is my question;
    This sections states that the diameter cannot exceed 1/3 etc...
    And after which, it goes on to state simply "holes" but does not reaffirm the 1/3 standard but I'm sure its implied. However, I take this as holes of any size cannot be located closer than 2" etc...?

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  2. #2
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
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    26,252

    Default Re: holes bored into beams

    Quote Originally Posted by Marc M View Post
    Here is my question;
    This sections states that the diameter cannot exceed 1/3 etc...
    And after which, it goes on to state simply "holes" but does not reaffirm the 1/3 standard but I'm sure its implied. However, I take this as holes of any size cannot be located closer than 2" etc...?
    Correct on both:
    - maximum allowed size of any hole is 1/3 the depth of the member
    - minimum allowed distance from hole to edge is 2"

    A 2x12 is 11-1\4" deep; 11-1/4" less 2" = 9-1/4" less 2" = 7-1/4", however, 11-1/4" divided by 3 = 3-3/4" for a maximum size hole of 3-3/4" located no closer than 2" to either edge. There is an area of 7-1/4" in the center of the 2x12 in which that 3-3/4" hole is allowed to be made (center of depth, not center of span).

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  3. #3
    Join Date
    Nov 2011
    Location
    Oregon, USA
    Posts
    333

    Default Re: holes bored into beams

    It's always a good idea to keep any holes as close as possible to the neutral axis of a beam. That's where the bending stress in the beam is actually zero.


  4. #4
    Join Date
    Oct 2009
    Location
    michigan
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    421

    Cool Re: holes bored into beams

    Quote Originally Posted by BridgeMan View Post
    It's always a good idea to keep any holes as close as possible to the neutral axis of a beam. That's where the bending stress in the beam is actually zero.
    Not exactly zero, but minimal enough to be ignored in this issue.
    The NEC also addresses this issue. I once rejected a rough insp. do to this very concern and since the building inspector had not called it out.... turds hit the big fan.
    Being a spec-home, the builder obviously did not want to replace/repair all the floor joists.
    I stood firm and eventually a repair solution was agreed upon by my building dept and the builder.

    The building inspector, who's a great guy, was embarassed he missed this one. However, I was the 'ba guy' for doing my job as far as the builder and developer were concerned.
    I lost sooo much sleep over this hehe


  5. #5
    Join Date
    Nov 2011
    Location
    Oregon, USA
    Posts
    333

    Default Re: holes bored into beams

    Quote Originally Posted by bob smit View Post
    Not exactly zero, but minimal enough to be ignored in this issue.
    Using working stress analysis, theoretically speaking and only at a very finite point, it's impossible to transition from bottom flange tensile stresses to top flange compressive stresses without passing through a point of zero stress. Either that, or a lot of college engineering textbooks are wrong, along with a few thousand engineering professors.


  6. #6
    Join Date
    Oct 2009
    Location
    michigan
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    421

    Default Re: holes bored into beams

    Quote Originally Posted by BridgeMan View Post
    Using working stress analysis, theoretically speaking and only at a very finite point, it's impossible to transition from bottom flange tensile stresses to top flange compressive stresses without passing through a point of zero stress. Either that, or a lot of college engineering textbooks are wrong, along with a few thousand engineering professors.
    Not the forum for us to discuss, but it's hard for us to resist
    There is that 'finite point' but in practical terms, it its to be ignored just as the measure of distance from tension to compression -thru that finite point- being some linear and some exponential quality is not for this forum. oops


  7. #7
    Join Date
    Mar 2012
    Location
    Lansdale, PA
    Posts
    876

    Default Re: holes bored into beams

    Quote Originally Posted by bob smit View Post
    Not the forum for us to discuss, but it's hard for us to resist
    There is that 'finite point' but in practical terms, it its to be ignored just as the measure of distance from tension to compression -thru that finite point- being some linear and some exponential quality is not for this forum. oops
    ???...Probably should stay away from commenting on structural theory.


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