Hi all,

Need to run a 2" drain line through some sistered 2x10 joists, preferably at an apx. 45° angle to the length of the joists. Can I bore these holes diagonally, or would it be better turn cross perpendicular to the joist, cross straight through it, and then turn back again with 45s? Also, since these joists are sistered, is there some special boring bit to get all the way through the 4" thickness?

Thanks in advance!

Rob

If you have to go through them, you are wise that youu're not planning to notch them at the bottom. A two inch notch at the bottom would reduce the strength to that of an 8 inch board from my understanding.

I do not know how your drilling would affect your situation, but one idea for either type of hole, would be to drill a pilot hole at the angle you choose... 90 or 45... then use a spade bit very carefully to dig out the hole. One side will dig in first, and the other side would be later if you do the angle hole. It could kick back on you and be considered very dangerous. I have drilled similar holes, but going very slowly to make sure drill does not bind... If it is possible, you might drill half way through from each side to prevent a lot of splintering at the end of your drilling.
Again, I don't know the effects of weight load or anything like that where you are thinking of drilling, so I can't offer any thoughts on that type of thing...

The strength of the beam is best if you drill at the center.

The easiest way I see to do this is to fasten a piece of wood that's cut at a 45 degree angle. This is your sacrificial starter, so that the flat wood bit starts on a perpendicular surface.

The flat wood bits are available for power drills and for a hand brace

Shown here:

Garrett Wade
.

The bits can also be purchased in an adjustable version such as these: IRWIN Adjustable Wood Bits

If you want to drill holes parallel to the joists you should be able to do it with a right angle drill, a extra ling drill bit and a hole saw.

6" drill bit here: Drill Bits
Really doesn't matter what size. Probably 1/8 to 1/4" for a 1/4" pilot bit on the hole saw.

Drill through both joists using the 1/8-1/4" bit. Then one side using the hole saw and then the other side using the hole saw.

You might consider bracing the hole with a steel plate with a hole in it and through bolts.

I used to be able to do those calculations and even figure out what size steel plate and the number of bolts and pattern needed to restore the strength.

A friend of mine made an additional suggestion to pass along to you. Consider using a metal sleeve in the hole for your pipe to pass through in case of any splinters or other issues that might result to damage on your pipe.

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Originally Posted by newpz

Hi all,

Need to run a 2" drain line through some sistered 2x10 joists, preferably at an apx. 45° angle to the length of the joists. Can I bore these holes diagonally, or would it be better turn cross perpendicular to the joist, cross straight through it, and then turn back again with 45s? Also, since these joists are sistered, is there some special boring bit to get all the way through the 4" thickness?

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Can you cut the existing piping back far enough to be able to hit the joists straight on?

That would certainly be preferable to destroying the integrity of the framing members.