cutting holes in joists for wire

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Old 12-22-08, 07:52 AM
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cutting holes in joists for wire

I need to put holes (5/8 or 3/4") in joists to run wire. I know in the engineered wood joists that there are very specific instructions on where holes can be cut and what size they can be. You have to know the span and then they say don't cut any holes in weight bearing zone X feet from bearing walls, etc. Any restrictions for plain old sawn lumber? I know to put the holes in center of the joists in reference to the joist depth, but what about in reference to the length? for example, I have 2x8 joists that span about 9foot. I would put hole about 3 3/4 inches from bottom (center of 2x8). Can i put hole anywhere along the 9' span of the joists or do I have to avoid the area near the weight bearing walls?
 
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Old 12-22-08, 09:02 AM
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drilling holes

well in reading your question I see that the floor joists your referring to must be in an older home. So my personal thought is you have to one determin how many holes your planning on drilling. then the location of the wholes needs to be the smartest route possible. In most cases when your house was built there were areas where your electric lines were run, and those areas is where you should run your new electric lines, but if your having to drill new holes go the smartest route, and stay as high as you can, this will keep the strength in the joist. Also if you can surface mount the wire this is generally the best way. then you do not alter the joists integrity, and you can go the shortest route, thus saving you money on wire.
 
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Old 12-22-08, 09:28 AM
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We have 2x10's set on 12" centers spanning 12 feet. Builder drilled two 5/8th holes for wire runs. One about a foot off the wall and the other in the center. 20 year old house - no problems so far....
 
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Old 12-22-08, 09:33 AM
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this actually is an addition. Because my old general contractor (now bankrupt!) poured the foundation too high, I had to re-engineer the floor and instead of having one LVL in center of room with 2x10 joists, I now have two steel beams which makes my spans shorter and was able to use 2x8 to get floors to line up.
 
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Old 12-22-08, 11:29 AM
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Cutting and Notching

Here is Massachusetts code.

5502.8.1 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 the depth of the
member. The tension side of members four
inches (102 mm) or greater in nominal thickness
shall not be notched except at the ends of the
members. The diameter of holes bored or cut
into members shall not exceed _ the depth of the
member. Holes shall not be closer than two
inches (51 mm) 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 two inches (51
mm) to the notch.

5502.8.2 Engineered Wood Products. Cuts,
notches and holes bored in trusses, laminated
veneer lumber, glue-laminated members or
I-joists are not permitted unless the effects of
such penetrations are specifically considered in
the design of the member.
5502.9 Fastening. Floor framing shall be nailed
 
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Old 12-22-08, 11:41 AM
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thanks. that is helpful, but it is missing part about "diameter of holes...shall not exceed_the depth of the member" Doesn't say the percentage or fraction?? for notches it says 1/6 but not given for holes?? I was using the 2" guideline. I also thought that you were to not bore holes or notches in middle third of span, but it seemed strange to me since this is exactly opposite of what is recommended in the wood I joists. I have the tables from boise cascade for my I joists and the restriction is that you are limited in how close to a weight bearing wall you can cut. The center of span is fine. Anyone know why there is this difference?
 
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Old 12-22-08, 11:44 AM
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In re-reading I guess you are NOT limited to outer thirds for holes, only for notches. Correct?
 
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