Re: Hole Diameter for running cable

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Jeff Volp" <JeffVolp@xxxxxxx> wrote in message news:VBhbh.119481

<stuff snipped>

> > the holes add up.
>
> I know what you mean about holes.  The main trunk down our center hallway
> fills two 1" diameter holes.
>
> Maximum stress on a joist is at the top and bottom surfaces.  All the
center
> really does is to keep the top and bottom aligned properly.  It does not
> compromise the strength of a joist at all if you drill a hole through the
> center of the beam.  While it may be permitted, I would avoid cutting ANY
> notches into the top or bottom surfaces.  That will severely compromise
the
> strength of the beam at that point.

Agreed.  When you see something like a small crane arm that's actually got
huge holes as part of the boom you realize that the center's doing very
little of the work in terms of load support on an average beam.

> Today's engineered joists are I-beams with structurally strong top and
> bottom sections separated by flimsy wafer board.  There are even
pre-stamped
> knockouts in that center section.  Those fragile looking assemblies can
> support incredible spans.

I've seen them using trusses made like that to span incredibly large areas
without needing floor columns but a lot of that strength comes from the
multiple plys used to create the members.  Old, monolithic wood joists
probably lose a lot more strength by having a hole drilled into them than
any sort of laminated material.  Is it significant?  Probably not.  Not
until that once-in-fifty-years snowstorm that adds a few extra tons of load.
(-:

--
Bobby G.