My one-story house with crawl space has 26' long floor joists
supported at midspan by a girder. Is there any reason not to to drill
holes through the joists directly above the girder? I'm just
wondering if the loading pattern over the girder is different than in
the unsupported section. There is a 2x3 bearing wall above the girder
that supports only ceiling joists.
You can drill reasonable sized holes in joists provided you place them
on the centerline without significantly reducing the load bearing
capability. It is best to keep them in the third of the span on each
Sorry, I guess my question wasn't clear. I'm familiar with the rules
for drilling holes in joists through an unsupported portion of the
span. My question is just whether there is any special consideration
with regard to drilling a hole directly over a support, e.g. a girder
with a bearing wall above.
Draw 45 degree lines up and out from the top of the girder to the top
of the joist, and down and out from approx. where the wall above is.
You should in, theory not drill there, without adding blocking first,
because that section is under compressive loads. In practice,
a 1/2" hole is unlikely to matter much. OTOH, just getting a drill
IN there is going to be a pain in the ass. My drill with a
1/2" spade bit in it is more than 14.5" long.
Good, that's the sort of answer I was looking for, thank you. I ended
up drilling 12" and 15" away from the edge of the girder at the
midline of the 9.5" deep joists. So I should be clear. The bearing
wall is roughly above the girder or slightly offset to the other side.
I'm using a 3/4" hole for 5/8" OD tubing.
I have a right-angle chuck (from Harbor Freight) that is invaluable in
this situation. Still a pain with all the wood chips raining down.
I'm talking about a 3/4" hole for plumbing supply line in a 2" x 9.5"
No 2 DF joist. I know that's no problem in the outer third of an
unsupported span. I'm just wondering if there are different rules for
a hole in a joist directly above a support and below a bearing wall,
since I imagine the usual loading (top half of a joist in compression,
the bottom half in tension) would not apply.
The force immediately adjacent to the bearing point is entirely shear,
so a hole that small wouldn't matter for your one story house. I'd be
reticent about locating it there for other reasons, but probably not a
How old is the house that you have 26' long dimensional joists?
When you say shear, is that the same as compression perpendicular to
the grain? I would think this would apply over the entire bearing
surface, not just at the boundary of the bearing surface.
Could you explain? I can locate them anywhere I want, I just thought
that over the girder would be out of the way. Would a 3/4" hole along
the neutral axis of the unsupported portion of the joist be better
(strength-wise) than a 3/4" hole over the bearing surface?
1908. Too bad the joists are No 2 or No 3, there are some knots, knot
holes and splits. Perhaps I should closely check the middle parts of
the unsupported spans for such defects and apply gussets where needed.
I did sister (without jacking) the two joists under the cast iron
bathtub sitting at midspan and running parallel to the joists, the sag
of the old 9.5" deep joists was only about 1/4" at midspan, judging
from the fact that the new 9.25" deep joists were tight to the
supports at the girder and exterior wall and tight to the subfloor at
I only need a 1/2" pipe, so I'm going to use soft copper (5/8" tube).
I was pleasantly surprised to find out that locally it is only 20%
more expensive than hard copper type L ($1.20/ft for soft copper,
$1.00/ft for hard copper).
Because it supports the 26' 2x6 ceiling joists at midspan? This is
I would suggest you consider PEX tubing for your fresh water re-pipe.
I've done the soft copper thing & it sure does start out soft but work
hardens in short order (esp with me on the throttle). I'm done with
copper (even though that's all I even used) PEX is the way to go. I'm
facing a re-pipe in my current house (1930) , original galvanized steel
still in service in some places!
Unfortunately, PEX is not approved for use in California.
I was surprised that the soft copper is harder to work with than I
imagined. I just want to get a 16' length through 12 joists. The
best solution I've come up with so far is to run a rope through the
holes in the joists, tie a knot in the end, feed the knot into the
soft copper, crimp of the end of the copper down to capture the knot,
and pull on the rope with a come-a-long. Still a serious pain.
A friend's brand new house Victorville is plumbe with red & blue PEX.
Maybe it's just the PR of Berkeley that's behind the times?
Also lots of municipal water works use HDPE for supply lines 12" to 24"
You should have no problem drilling a hole in a joist at that
location, of course a lot depends on the size of the hole. If you have
any doubts, you could always nail an additional piece of 2x6 to
provide some additional support, but I really don't think that it is
necessary in most cases.
A 2x6 in compression, even with a 1" hole in it is a formidable
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.