Any opinions on the use and cost effectiveness of eng. floor joists vs. traditional stick framed subfloors. Spans will be 12′, 16′, 14′. Thanks in advance.
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Replies
For a span of 16' you will just about have to go to an engineered floor system unless you want to use dimentional lumber larger than the standard 2x10.
Regardless of what you use, don't max out your spans (as stated on a span table).
Around here, everyone seems to use engineered floors, due to cost. Some prefer the truss style joists, easier to run wiring / plumbing through, but most prefer the i joists, for two reasons: they are lighter, so easier to manhandle, and more importantly, they can be cut to length on site, whereas teh truss style has to be made to suit.
Just make sure your subs understand how to penetrate them: the inspector wasn't happy that the plumber put a 3/4" hole through a lvl beam, 4" from the end (it is definitley a no-no), but he accepted it. I'm glad he didn't come later to see the electrician do THE SAME THING TO THE OTHER END OF THE SAME BEAM, and the hvac guy start to "open up" the web of an i joist to use as a duct....Good Grief!
I love I-joists, use them every chance I get. Straight, strong, light, consistant sizes...can't say enough good things about them.
Use them for rafters when I get the chance, too. Overhangs take a little longer to frame, but I still think you come out ahead in the long run over dimensional lumber and there's no question you get a flatter roof.
Great innovation - right up there with fiber cement siding and pneumatic nail guns.
Overhangs take a little longer to frame
Don't necessarily have to. Cut the rafters even with the top plate (either plumb or perpendicular as the o/h allows). Build the o/h by sistering 2 x 6 to the rafters. First off, you get a slightly higher soffit elevation--better for ventilating the roof over the top of the ceiling insulation. Second, you are not, per se, framing the o'h with more expensive material. Best reason is to simplify the rafter cuts.Occupational hazard of my occupation not being around (sorry Bubba)
Yeah, but you still have to block out the web of the I-joist. And if you frame rake overhangs by notching 2xs flat into the top of the gable rafter or truss, you're gonna have to learn a few new tricks for framing with I-joists. I'm not saying it's anything anyone with half a brain can't figure out, just that it takes a little more time (money).
but you still have to block out the web of the I-joist
Bugged me for a while, but found a way to not have to. Run the 2 x 6 under the top flange (ought to be about 2x the o/h in length). Now, you just need to run some "strapping," if you will, of the correct thickness to match the top of the BCI (or scab on blocking along side the 2x6 to the right height.
One very neat thing is that a lot of this can be done down on the ground with the less experienced help. If you are tough enough (or have the right machinery, and, more importantly, need), you can lift pre-assembled sections up (much better for narrower overhangs, though). Saw it done once, where the o/h and soffit were framed up together, on a ground level jig. Looked like a lopsided "b," all of the framing was aligned in place, rafter by rafter. Went right quickly.Occupational hazard of my occupation not being around (sorry Bubba)
Can't have a thread on floor joists without me bringing up the Floor Vibration thread.
You'll probably get more responses if you ask specific questions. I'd say I-joists go into roughly half the new homes around here. (But that's just a guess) Wood webbed floor trusses run about 5%, and conventional lumber makes up the rest.
There are fire concerns with I-joists, but no one seems to talk about that much.
He often broke into song because he couldn't find the key.
Thanks for the help. I'll give some more info. This project was supposed to be a remodel/ addition. After our initial tear-out, we couldn't find anything worth saving. Cracked and rotten joists and no sill plates!, foundation is 5" out of level from back to front. I'm going to form and pour the old foundation to match the new. The spans for the floor joists would be 12', 16', and 14'. Money is a factor, but quality and structural integrity come first. I'm looking at either I-joists or 2x12's. I appreciate all info.
If you can come up with a dimensioned drawing for the floor or floors in question, indicating bearings below, loads from above, openings, etc., your lumber supplier will be happy to have his source for engineered lumber figure the job for you. Once you and your lumberyard person have that drawing, you can see whether sawn lumber can do the same thing and price it both ways. Or were you planning on building this booger with some notes and sketches done on lumber scraps?
I've got the prints, just looking for personal opinions.
I don't have a lot of thoughts for you, but here are a couple.
The upsides are that I-joists are straighter than any lumber you're gonna buy at the yard. Some of them have wider flanges which makes the subfloor go down easier. The fact that you can buy them in long lengths (48' around here) means you don't have to lap joists over bearings.
The downsides are that they're a bit more expensive to buy initially than regular 2X lumber. There are specific details that you have to follow for stuff like point loads, bearing walls that stack over walls below, etc. Threre are also specific restrictions on where you can cut holes for mechanicals.
If you're spanning 16' I would strongly suggest 11 7/8" I-joists. You can probably get 9 1/2" I-joists that will span 16', but you won't be happy with the performance.A closed mouth gathers no feet.
Pretty much in agreement with what Boss wrote.
Engineered joists may be pricier up front, but you know that each piece is uniform, unlike 2-by stock. No wane, no checks, excessive crown, all the same depth, etc. Setting I-joists is usually faster than setting 2-bys.
When getting close to the span limit, it's often better to go with a deeper I-joist than to decrease the on-center spacing.
I-joists do have the 'trampoline effect' due to the platform being so uniform that it's easy for it to reach a reverberation frequency. Use strapping on the bottom sides of the platform, screw the rock to the strapping.
Most trades are familiar with drilling schedules for I-joists, but have them sign off on it anyways, because some yahoo will always try to pop a hole where a hole is not allowed. Staple a couple of schedules to the bottom flanges of the joists so they hang down into space below for easy reference. Also, include a schedule with each set of plans you give to the subs. Easy, zero cost, and it protects you on your end from the "no one ever told me" syndrome.
For any hangers, run a bead of contruction adhesive inside the hanger before placing the I-joist.
Glue/screw the subfloor to the I-joists. Better performance, and the span charts are usually predicated upon that. Advertised spans are less if you don't.
Think L/480 as the minimum, L/720 as much better.
Always order them slightly longer than you actually need. Sometimes the flanges get crushed or or slightly delaminate in the process of shipping/storage/dumping off at the jobsite. If you need a 16' joist, and they delivered you a 16' joist with 6" of damaged flange, you've got a useless piece of wood...unless it can be cut down for another application.
Review all details before using...crush blocks, web stiffeners/fillers, fastening schedules, etc. They can be a big time-saver, as long as you install them right...the first time.
BH I went back to the thread and wonder if you could send me the chart or look up and confirm my suspicions about my trusses. I have 38 ft, 12" deep trusses @ black diamond spacing with a 2x6 support wall mid point.
A cat running through the room ( 33x19) is like a suspension bridge. I put some storage shelves in the basement about in the middle and ran a 2x6 under most of the trusses which helped. It is not bad enough to do anything serious about it but it is aggravating. Tell me how bad it hurts or is that hertz?
" I have 38 ft, 12" deep trusses @ black diamond spacing with a 2x6 support wall mid point. "
A 19' span for 12" deep trusses isn't much of a stretch. (Although I personally like to limit 12" deep trusses to 18') According the the spreadsheet, the floor should vibrate at around 14.5 to 15 hertz. The lumber grade affects the number, and I just guessed at that.
"A cat running through the room ( 33x19) is like a suspension bridge. "
I don't follow what you mean there.
If you're looking for suggestions, I have 2. First would be to ask if there is a double vertical over the bearing wall, with a gap between them. If there is, the top chord was probably meant to be cut at that point to separate the 2 spans.
The idea behind this is that if one side of the span is heavily loaded (Like with kitchen cabinets and a fridge) the other side can be "picked up" a bit, which affects how the floor feels. Cutting the top chords with a sawzall (Over the bearing and between the verticals) can separate the 2 spans and change the way the floor feels.
The second suggestion is to install 2X6 strongbacks at mid span. If you don't know what these are, let me know and I'll try to come up with a picture.Never trust a stockbroker who's married to a travel agent.
Thanks, Boss. The cat thing was meant to describe the room size of 33x19 and when one of our slightly overweight cats runs through the room you can feel vibration. The bridge part was comparing it to the old bit about how easy it is to set up vibration on a long highway suspension bridge. I have unused chases at midpoint in each half for heat ducts that we did not use. We ran 2x6's nailed to the bottom chord and vert. member in the vertical orientation. There are double vertical members but there was no mention about cutting the top chord. It is too late now.
If I had it to do over again I would use deeper ones and drop down one more block ( this was an addition).
Adding the strongbacks in the duct chases should have made a differnce in the "feel" of the floor. Adding a second one in the OTHER side of the chase might possibly help.
Adding more rows of strongback might also help, but it's hard to tell. And they're generally a pain to get in since the trusses are fairly shallow.
The top chords could still be cut with a sawzall, but it wouldn't be easy.What's the definition of a will? (It's a dead giveaway.)
Thanks again, more sage advice. All things considered it came out pretty well overall and the little bounce is acceptable. Had 40 folks in for grandaughter's first birthday four years ago and noticed no problems. Just load it down. I think part of the reason is almost all of the heavy furniture is on perimeter and wide open space like a drum. It does cause some rattle in the china cabinet up against the wall. The heirs can fix it when they get it.
The heirs can fix it when they get it.
Perfectsolution to a minor problem (|:>)
SamT
I like the concept of the TJI's but there is a serious problem if you have a fire. The bottom flange can not stand much damage before failure. I prefer the use dimensional lumber and pre-made x-braces. These are made by Luxor Industrial Corp. Web-www.luxorcorp.com
These things are so cool. They add to the span limits, but more importantly, they get rid of a LOT of the bounce you feel in the floor. Price---about $ 7.25 per for a 2x10 on 16'' centers. Trade name--IBS 2000.
I used them in my own house.
Curly
Restoring the past for the future.
In addition to those already commented on, one great benefit of the I joists is that they are very stable across the grain. If you have noticed that most of your drywall nail/screw pops are in 2 story areas, you are not alone. A sawn 2X10 or 12 will move a lot as it dries out from new and then changes over the winter and summer with changes in humidity. The I joist and maunfactured rim products are much more stable in that regard, and will drastically cut your "beltline" drywall woes.