Enlarging holes in 2x8 joists

[Tpt life]

24 minutes ago, Ronn W said:

You can easily use up to 2" holes in 2x10 joists.  You can move over about 6" from your current holes and drill new.

There are 2 considerations in the strength of a joist.  One is "shear" which is greater near the supports and least in the middle of the span.  The other is bending which is greatest in the center of the span and least near the supports.  Shear is resisted by the entire cross section of the joist so you don't want holes one above the other, but holes in a row about 4 to 6" part would be OK.  Bending is resisted most by the top 2" and the bottom 2" of the joist so you do not want keep your holes in the middle of the depth of the joist. Holes are OK in the center third of the span where the shear is the least provided they are in the center of the depth of the joists.  Actually notching a joist is never a good idea without an analysis.

Most of what you just said in the second paragraph fails coding. I did not enter this discussion to talk load physics. I entered to prevent insurance lawsuits and city cease-and-decist orders. 

[Tom Cancelleri]

The location of the holes is definitely within code. 

[Ronn W]

1 hour ago, C Shaffer said:

Most of what you just said in the second paragraph fails coding. I did not enter this discussion to talk load physics. I entered to prevent insurance lawsuits and city cease-and-decist orders. 

 

I respectfully disagree.  Shear is least is the center of the span. In fact the shear at exactly center span is zero if the joist is evenly loaded.  Center third  is the best place for holes provided they are near the center of the depth of the joist.  Notches are different and, as Tom's sketch suggests, " no notches" in center third is correct. 

[Janello]

6 hours ago, Ronn W said:

 

I respectfully disagree.  Shear is least is the center of the span. In fact the shear at exactly center span is zero if the joist is evenly loaded.  Center third  is the best place for holes provided they are near the center of the depth of the joist.  Notches are different and, as Tom's sketch suggests, " no notches" in center third is correct. 

Wrong. You need to revisit this, because it's just not true with conventional lumber. You might be thinking TGI's which have a different set of rules. 

[wtnhighlander]

I don't have a clue about this particular circumstance, but I would point out that building codes are not universal. Even in the state where I live, they vary somewhat by county. Best to confirm with your local building inspector.

[Janello]

Vinny Gambini: I'm sorry, I was all the way over here. I couldn't hear you. Did you say you were a fast cook? That's it?

[Mr. Tipton nods in embarrassment]

Vinny Gambini: Are we to believe that boiling water soaks into a grit faster in your kitchen than on any place on the face of the earth?

Mr. Tipton: I don't know.

Vinny Gambini: Well, perhaps the laws of physics cease to exist on your stove. Were these magic grits? I mean, did you buy them from the same guy who sold Jack his beanstalk beans?

[Tom Cancelleri]

 

[wdwerker]

All of the approaches mentioned will work, some slower than others. Time spent doing some layout work to align the holes will make pulling heavy wire much easier.

[AJ_Engineer]

 

16 hours ago, C Shaffer said:

The center of the joist most certainly does matter. This is why you are limited to the outside thirds of the span. Drill nowhere in the center third. 

 

16 hours ago, Chestnut said:

Wrong center center height wise not length. You are correct on the length part.

Correct that notches are not permitted in the center third of the length for joists per NDS, IBC and IRC (which is likely your governing code). Holes on the other hand are allowed anywhere along a joist. Limits apply to the size they should be centered.

For studs you can bore and notch anywhere along them. For exterior/bearing walls notch to a max of 25% of depth, bore a hole to a max of 40% of stud width. For non-bearing walls the numbers are 40% for notches and 60% for holes.

IRC for joists. IRC for studs. Both have some good figures and match IBC.

[Tpt life]

I have never built a home in an inspected territory that would allow ANY clearance in the center third of the Span. This means notch or hole. Please check your local coding before doing any work. Holes being allowed in the center third of the span almost always indicates web I-joists. They don't matter in this thread as Tom specified 2x8. I am not in a very restrictive environment. Our coding is rather loose. I would not assume my local enforcement is picking on this one area out of context. 

[Janello]

24 minutes ago, AJ_Engineer said:

 

 

Correct that notches are not permitted in the center third of the length for joists per NDS, IBC and IRC (which is likely your governing code). Holes on the other hand are allowed anywhere along a joist. Limits apply to the size they should be centered.

For studs you can bore and notch anywhere along them. For exterior/bearing walls notch to a max of 25% of depth, bore a hole to a max of 40% of stud width. For non-bearing walls the numbers are 40% for notches and 60% for holes.

IRC for joists. IRC for studs. Both have some good figures and match IBC.

Your link to IRC for joists is not difinitive. What I can tell you without question is this. Where Tom lives, if you drill out the middle third of a span of conventional lumber, you're failing inspection and you are paying the framer to replace all of those joist you hacked into. Period!

It's clearly stated in the National Standard Plumbing Code.

[shaneymack]

Not sure why no one is taking into consideration tji's vs solid lumber. Big difference. John already mentioned this. Its different depending on the joist

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[Chestnut]

34 minutes ago, shaneymack said:

Not sure why no one is taking into consideration tji's vs solid lumber. Big difference. John already mentioned this. Its different depending on the joist

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Aren't I-joists even more lax on hole location and size? I've seen ducting run through the web. Also there is open web trusses but those are even easier yet no drilling necessary.

[Janello]

24 minutes ago, Chestnut said:

Aren't I-joists even more lax on hole location and size? I've seen ducting run through the web. Also there is open web trusses but those are even easier yet no drilling necessary.

Short answer is yes.

[Tom King]

What county and town is it?  I'd like to call and see what they call for.  I've never run into a jurisdiction that didn't follow the IBC.  If indeed they don't, this will be good to know so that I will always call and ask that question when working in a place I've never worked in before.

[Tom Cancelleri]

Loudoun County VA. I thought VA was IBC/IRC

[Tom King]

Beautiful country there.  I know my way around the  Middleburg area fairly well from horse stuff over the years. 

I drilled a series of 3-5/8" holes in some 8" floor joists once, and all involved, from owner, to inspector, to engineer, were okay with it.  The joists were 36 foot long 4x8's for the third floor in an early 19th Century house.  We put a bathroom on the third floor, as well as the other floors.  The house had never had a pipe or wire in it before.  That bathroom was put in what was wasted space in the attic because of the way the roof was framed, and no change to the original rooms or floorplan was made.

Those holes were put right over a bearing wall, and pure heart of Heart Pine.  The 3" drain pipe was behind a knee wall, so taking the floor up didn't matter at all. We ran HVAC lines above that same area to the air handler that served the second and third floor. The plumbing drain pipe went into the attic of a modern kitchen addition, sitting on brick piers to match other "porches" on the house.  The drain continued to  the outside wall where it dropped down and went through one of the brick piers.  You cannot look around that house, or in the basement, and see a wire or a pipe anywhere, but it has bathrooms, and a good HVAC system.

Water supply lines are home runs of PEX inside glued plastic electrical conduit, so they can be pulled out and replaced in the future, and any leak will be carried away from the house structure.

[Ronn W]

12 hours ago, AJ_Engineer said:

 

 

Correct that notches are not permitted in the center third of the length for joists per NDS, IBC and IRC (which is likely your governing code). Holes on the other hand are allowed anywhere along a joist. Limits apply to the size they should be centered.

For studs you can bore and notch anywhere along them. For exterior/bearing walls notch to a max of 25% of depth, bore a hole to a max of 40% of stud width. For non-bearing walls the numbers are 40% for notches and 60% for holes.

IRC for joists. IRC for studs. Both have some good figures and match IBC.

Correct.