Replies

1. 
   JTC1 | Jan 12, 2010 04:03pm | #1

   Yes, it can be done with a relatively painless bit of sistering of the original 2x10 joists.

   Just exactly how to figure out how long the sistered section needs to be, I do not know. A decent engineer will laugh at the simplicity of this problem.

   I had a situation on a recent bathroom where the HVAC guys installed the duct for a bathroom fan in the wrong bay. I needed the fan to be in the next bay over in order to center the fan over the shower. Fan duct exited through some rather elaborate trim to the outdoors - not the best to move the duct and re-do the exteroior trim.

   I called an engineer, gave him all of the specifics and told him I needed to bore a 4-1/4" hole anywhere between x and y inches away from the exterior wall.

   He faxed me a plan that evening - sister with a A" long 2x12 nailed with 16d nails B" on center and clinched, bore hole at Z inches from the exterior wall in center of joist hieght. Mailed me a stamped sketch the next day.

   No bill, so it must have been simple.

   Jim

2. 
   rdesigns | Jan 12, 2010 04:23pm | #2

   Are the joists solid-sawn or TJI's?

   TJI's might allow holes of that size if you are at least 2 feet from the end. Check the manufacturer's website for allowable hole sizes and hole spacing.

   If they are solid-sawn, you will definitely need an engineer as JTC says, because the code will not allow that much cutting without an engineer's blessing.

1. 
   shawncal | Jan 12, 2010 05:45pm | #3

   These are solid sawn joists. Just out of curiousity, what does code permit?

1. 
   rdesigns | Jan 13, 2010 10:39am | #4

   Since notching would be out of the question, I'll give you the limits on bored holes:

   The diameter of the hole can't be more than 1/3 the depth of the joist--so, in a 2 x 10, the actual depth would be about 9-1/4", so you'd be limited to not much over a 3" hole. BUT, the hole can't be closer than 2" to the top or bottom of the joist, so if you are running a drain line over much distance, the slope of the pipe can cause you to creep beyond that 2" margin.

   The hole can't be closer than 2" to any other hole or notch.

   Your building inspector may be able to make some allowances, however, based on the fact that the limitations above apply to joists that are at their maximum spans and loads. In your case, you mentioned an 8'-6" span, and a 2 x 10 is more than what's required for that span if it's carrying a normal floor load from above. So, it would be reasonable to allow somewhat larger holes and smaller margins in your particular case.

   Here's hoping you have a reasonable and experienced BI.

3. 
   SteveInCleveland | Jan 13, 2010 11:56am | #5

   How many joists are involved?

4. 
   PatchogPhil | Jan 13, 2010 12:12pm | #6

   Shawn

   Does your layout allow running the DWV between the joists a short distance to a partition wall or outside wall? Then you create an aestetic bulkhead (aka interior soffit) in the corner of the wall-ceiling (or verticle corner chase) to run the DWV to where you need it.

5. 
   mikeys | Jan 13, 2010 12:35pm | #7

   http://www.co.clark.wa.us/commdev/documents/building/details/rafterjoistnotchingandboring.pdf

   This is a simple diagram I found.

1. 
   rdesigns | Jan 13, 2010 12:41pm | #8

   Picture's worth a thousand
   Picture's worth a thousand words.

6. 
   davidmeiland | Jan 13, 2010 08:27pm | #9

   In that sketch... I'm not
   In that sketch... I'm not sure if joist depth "D" would be 9-1/4" or 10" when referring to a 2x10... but I suspect it's 10". Milwaukee knows you need to run 3" pipe thru joists and they make a 3-5/8" self-feed bit just for that purpose. I have seem many jobs where 3" was run thru 2x10 with no inspection problems, even with gnarly inspectors, so I *think* it's OK, but I could be wrong.

   The main issue with running thru joists is having to get a long piece into place, or coupling multiple short pieces together.

1. 
   mikeys | Jan 14, 2010 12:53pm | #10

   The sketch I posted was not the one I wanted to find.

   The page I was looking for specifically said use actual joist depth, not nominal.

1. 
   davidmeiland | Jan 14, 2010 10:47pm | #11

   I just looked at my '03 IRC
   I just looked at my '03 IRC book and it does refer to actual joist depth (D) and states that D/3 is the maximum drilled hole, not less than 2" from either edge. I recall somewhere else that uses a figure of 40% of D, in which case the maximum in a 9.25" joist would be 3.7", or just enough for a 3" ABS pipe. Where's Plumbill when you need him? Hell, he may never deal with wood framing, so whaddya do?

   edit: realized that the 40% figure applies to holes drilled thru exterior wall and loadbearing studs, not applicable to floors.