New construction basement. Dimensions 35 x 60 (external). Engineer proposed two steel I-beams running the 35-ft way, then hanging floor trusses perpendicular to the steel beams. Question: Can the height of the floor trusses be 6″ taller than the height of the steel beam, so that they hang down below them, in order to allow a plumbing drain line to pass below the steel beam? I didn’t want to have to soffit-in for a plumbing run. Or, can a 4″ hole be cut into the steel I-beam? I guess I could look that up, but I thought I might find it here.
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Replies
1) As per drilling your steel: Ask your engineer. Asking a question of this sort at a forum of this nature is doing a disservice to yourself, the engineer, and your client.
2) Do you want the tops of your floor trusses substantially above the top of your steel?
3) Do you want the bottom of your trusses below the bottom of your steel? If this is so, you may be able to install a Fire-Rated suspended ceiling to hide your mechanicals. Your BI would have to be consulted, because the fire integrity of the steel and trusses would have to be maintained. Your BI may also make your wrap the structural iron with GWB.
Again, these questions are better left to your enginner, truss designer, plumber, and BI.
Edited 3/7/2009 4:43 pm ET by McMark
Edited 3/7/2009 5:17 pm ET by McMark
Floor truss designers have a lot of latitude in how they design the height of a truss.
Are you saying you want the top of the truss even or slightly above the steel beam and the bottom of the truss to be 6" below the steel beam?
What I said was for the trusses to hang down below the I-beam. But the trusses could also be flush with the I-beam at the level of the basement ceiling, and rise 6" higher than the I-beam at their tops, allowing the 4" drain line coming from the bathroom to get past the I-beam. I don't know which makes more sense. I'm just glad that several Breaktimers have kicked the idea around a bit today. It helps me. Thanks, everyone.
and rise 6" higher than the I-beam at their tops, allowing the 4" drain line coming from the bathroom to get past the I-beam.
Better talk to your plumber, 6" doesn't sound like enough. 4" DWV implies a toilet. You have to come out of the flange, turn 90, and drop 1/4" per foot from your toilet to the beam. 4" pipe is also 4 1/2" OD.
Alot to do in 1 1/2"
Edited 3/7/2009 5:59 pm ET by McMark
Better talk to your plumber, 6" doesn't sound like enough. 4" DWV implies a toilet. You have to come out of the flange, turn 90, and drop 1/4" per foot from your toilet to the beam. 4" pipe is also 4 1/2" OD.
Alot to do in 1 1/2"
It's a 30-foot run we're talking about, so yeah, we'll need 7.5" total vertical space available for the drop alone. The idea about hanging those floor trusses off the I-beam just isn't going to be practical. Dinosaur thought it was idiotic.
You may want to look at a different approach to the drain problem. When I design plumbing systems in new homes, I do everything possible to avoid drain lines running across a basement ceiling or along walls.
I always try to run the drains over to the basement sidewall between the floor joists and then drop through the floor right next to the wall and run the sloping horizontal section underground where it doesn't clutter up the basement ceiling. It's pretty easy to box in the pipe at a sidewall if necessary.
This makes for a nice, neat ceiling line. It is usually easy to do if the sewer line can leave the home that far below ground. It's harder to do if you have a septic system at the wrong elevation. You can also use a sump system this way and pump up if needed.
Bojangles,
Underground is quieter, too.
Ron
Good point !!
Why not more conventional and run 1 60' beam with the floor joists sitting on top?
or 2 35' beams with the joists running over the top?
Why not more conventional and run 1 60' beam with the floor joists sitting on top?
or 2 35' beams with the joists running over the top?
I was gonna say that.
'Hanging' trusses off the sides of a beam is just a dumb way to weaken the whole structure. No excuse for it in new construction. Designer oughta be dope-slapped.
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
'Hanging' trusses off the sides of a beam is just a dumb way to weaken the whole structure. No excuse for it in new construction. Designer oughta be dope-slapped.
Dinosaur
Well if that's the case, I guess we'll just sit the trusses atop the I-beams and excavate deeper to make up for the lost headroom. I was wondering how they were gonna hang those trusses onto the I-beams. If the trusses are running the 60-foot direction, with one I-beam at 20 feet and the second I-beam at 40 feet, then the plumbing drain can easily run as far as it needs to without any obstruction by the I-beams. Sounds like a plan.
Yep, that's the way to go if you can. We only use hangers to connect joists or trusses to the sides of a beam in a remodel situation where you don't have the headroom to lose.
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
You can hang the joists fron the steel without a problem, the problem will be if you want it higher than the steel. I have never seen it done.
I am not saying it can't be done, just I haven't seen.
You expect the steel to span 35', that is going to be some heavy beam!
I was hoping Boss Hog saw and responded, his advice is best, sorry!
Edited 3/8/2009 10:27 am ET by frammer52
I have no idea why you would think that hanging trusses off the side of a beam would weaken the structure. We do top chord bearing and mid chord bearing trusses all the time. There's absolutely nothing wrong with it.
You and Dinosaur may be talking at cross purposes. He may be thinking of TJs, not trusses. I know most true floor trusses I've used were top chord bearing. The truss guy always made a sour face if I wanted it otherwise.
I have no idea why you would think that hanging trusses off the side of a beam would weaken the structure.
Because I simply don't believe that any hanger is as strong as the truss or joist (or beam) itself. If they were, they would have to have the same section and scantlings, etc. as the structural member, and they don't.
If I'm wrong in that belief, edjumacate me, please....
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
Dino,
Hangers are working purely in tension and it just doesn't take much steel to support a tension load. The limit on hanger design is probably the fasteners' reistance to tear-out.
The joist or truss in the hanger and the beam the hanger is fastened to, is designed to a different spec in that they are usually designed to achieve certain deflection limits and that takes a lot more beam than it would take to just carry the load if deflection were of no consequence.
I'm with you completely on having the joists on top of the beam, though. It's just simpler and faster and better.
Ron
A hanger may not be as strong as having a truss sit on top of a beam. But if it's strong enough for any load that will ever be put on it, what difference does it make?In my career I've never heard of a hanger failure where they were properly installed. The only one I know if happened when they just stuck a couple of nails in them to get them in place, then never went back to finish nailing them.
A hanger may not be as strong as having a truss sit on top of a beam.
That's what I meant when I said using hangers weakens the structure. I probably should have stated it better, though, and said that using hangers produces a weaker overall structure than having the trusses sit on top of the beams.
But if it's strong enough for any load that will ever be put on it, what difference does it make?
None...but who knows what future owners may think is a reasonable load? Some of 'em don't think, actually. They just accumulate stuff and never pay attention to how much it weighs.
Just as a for-instance: A medium-sized collection of 1500-vinyl LP records and 7500 books (like mine) weighs far more than the design states for standard residential floor framing contemplate. (And yeah, I've got my joists sitting on top of a steel I-beam. Unlike a lotta ivory-tower bookworms and record collectors, I actually know how to do arithmetic....)
never heard of a hanger failure where they were properly installed. The only one I know if happened when they just stuck a couple of nails in them to get them in place, then never went back to finish nailing them.
Aye, there's the rub: that old demon Human Error again!
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
"None...but who knows what future owners may think is a reasonable load? Some of 'em don't think, actually. They just accumulate stuff and never pay attention to how much it weighs."
Aren't your footers, columns, steel beams, and joists designed to a "reasonable" load? Like it or not, any load can be exceeded with enough effort.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
Aren't your footers, columns, steel beams, and joists designed to a "reasonable" load?
Yes, but hangers will always remain the 'weak link' in the structural chain. Thus, I don't use them unless there is no other reasonable solution to the framing problem.
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
"...hangers will always remain the 'weak link' in the structural chain."
That's BS. They might be in some cases, but they certainly won't ALWAYS be.
You're taking your own personal preferences and grasping at straws to try to rationalize them.
Why is lemon juice is made with artificial flavor, while dish washing liquid is made with real lemons?
Come on, Boss. You already stated that a stacked frame assembly is stronger than one which depends on hangers; that's what I recommended to the OP to solve his utilities-routing problem and increase the overall strength of his framing simultaneously.
If you want to debate the strength of joist/truss hangers versus ledgers, toe-nailing, Liquid Nails, or friggin' Velcro, I'm not going to play. There's no point me bashing my face against the numbers built into design programs by anonymous engineers.
But my stuff doesn't fall down--and there are a few engineers around here who can't say the same. ;-)
I use joist hangers when they are appropriate...which means when the situation requires them. Usually that's a basement remodel situation where headroom is an issue, or attaching a low deck to a house where there's no room for a ledger below the joists.
However, I know I can create a stronger overall structure by designing it so the joists or trusses are stacked on the beams, and I do that whenever there's enough room to make it a practical and reasonable solution.
But I refuse to use joist hangers just because they exist. Hell, I refuse to use anything just because it exists. There's gotta be a better reason than that.
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
I never said that putting floor members on top of a beam was stronger - I just said I preferred doing things that way.As you said, there's no point in argueing with you about the idea that hangers are weaker than the floor members themselves. You're trying to pass your own opinion off as fact, with nothing to back it up with.
Vote Democrat - it's easier than working
Well, in that case, I misunderstood you when you said this:
From:
BossHog <!----> View Image<!---->
Mar-10 7:12 am
To:
Dinosaur <!----><!---->
(26 of 34)
117542.26 in reply to 117542.24
A hanger may not be as strong as having a truss sit on top of a beam.
Let's drop it, Boss. From reading back over this thread, it's obvious that we both agree the best way to do this is to stack the joists/trusses on the beam. The only thing we're arguing about is who is more entitled to that opinion--you or me.
Not worth arguing about...especially with a friend.
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
I think the problem is that one person is taking the phrase 'may not be as strong as' to mean 'becomes the weakest link in any structure ever built anywhere by any person at any time, no ifs ands or buts'.
Mind you, it does make for entertaining reading. For some reason, it makes me want to make a nice, crispy pizza crust.
For some reason, it makes me want to make a nice, crispy pizza crust
Yah--and now you've gone and made me hungry again.
Not that it takes much to do that, of course....
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
I think Boss can fix ya right up with a pizza crust recipe...
"
I think Boss can fix ya right up with a pizza crust recipe...'If Boss can't, I can; New Haven style, thin and crispy.BruceT
Consider it dropped. (But I was right)(-:
Q: How does a man know when his wife is losing interest?
A: When her favorite sexual position is next door.
"Consider it dropped."
Ahh... You must have been using joist hangers.
Otherwise, it wouldn't have dropped... {g}
Jon Blakemore RappahannockINC.com Fredericksburg, VA
"Yes, but hangers will always remain the 'weak link' in the structural chain. Thus, I don't use them unless there is no other reasonable solution to the framing problem."
You really could say the same thing about joists, beams, subfloor, etc. Why don't you refuse to build anything but slab on grade?
Jon Blakemore RappahannockINC.com Fredericksburg, VA
Yep, we could do it that way. I told the engineer to first take a look at keeping the space in the basement as open as possible, with no columns at all. And so far, this was what he came up with.
Don't drill the steel. The flooring frame work can be made to "drop" below the steel. But you will need to be sure the "plumbing drop" will be enough to meet code for drainage.
alot depends on the height of the steel I-beam... if it's a 12" beam... then a 5" hole in the center of the web... is pretty common and not hard to drill... a standard bi-metal hole saw will go through 3/8" steel alot faster than... makeing this post and reading all the answers...
yeah i guess you could ask your engineer... but if it's an issue thats the first thing i'd do ... vs try'n to figure a way around... drill'n a simple hole...
when a hole was questionable... we just drill the hole oversize then weld in a 6" piece of pipe into the hole...to act as a sleeve for the plumbing run...
p
BarabaraD
The engineer will have to design it, but there should be no problem in putting a hole through the webs of the beams in certain locations.
It's easier in some places than in others. For instance, at 1/4 and 3/4 of the length of the beam, if it carries a simple evenly distributed load, the internal shear will be zero, and that is the loading the web resists.
I'm sure there will be some complications here, like posts, which will change the picture, so don't pull out the cutting torch quite yet.
Ron
Barbara, the simple answer is yes, you can use "top chord bearing" trusses and build them as deep as you want and hang the bottoms below the steel beam. There is no limit to the amount of "hang".
Another option is to have the truss designer create a "chase" that is built into the trusses to accomdate your mechanicals.
I'm with frammer52 - I think it's best to put the floor members on top of the beam. Trying to recess a beam almost always causes problems with mechanicals.
If headroom is a problem, then pouring deeper basement walls may be your best bet. You aren't likely to get ALL of the mechanicals hidden in the floor trusses anyway, so somewhere you'll probably have something hanging down.
I'd suggest getting a floor truss layout and truss drawings from the truss manufacturer. Then take those to your plumber and HVAC guy and discuss the situation with them.
I've been doing truss design for 24+ years, and am often asked about situations like this. I very much prefer to try to sort it all out ahead of time rather than trying to come up with a solution after the fact.
You need to run this past your engineer. Just about anything is possible, but you need to let the engineer know up front what all the design issues are.
This includes routing and clearances required for the mechanical and electrical systems. If possible the floor plan is nice to have too.
at that meeting with the designer, engineer and plumber ...
ask the plumber how much an extra DWV run would be.
one that's right where it'll feed directly from the bath above.
more plumbing might be the quickest, easiest and cheapest route.
Jeff
Buck Construction
Artistry In Carpentry
Pittsburgh Pa