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Thread: Second Floor of Shop I-Joists or 2x12 Lumber

  1. #1
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    Second Floor of Shop I-Joists or 2x12 Lumber

    I just got the quote from my lumber yard on my 19'x30' floor system. I'd heard that I-joists were better and not much more cost. I liked the idea of the lighter weight vs solid wood as I'm hoisting them up 12' in my existing 26' high ceiling shop. I'm studying all the information I can on installing I-joists as I've never worked with them.

    The cost is $1984 for I-joists and 5"x12" LVL beams. The I-joists 16''OC span 19' clear and rest on LVL beams at each end. The 4- LVL's span 14' between the huge steel columns that hold up the 27' high roof. This is the specs from the I-joist supplier to meet 40 psf live load/15 psf dead load. This meets residential code for a floor full of people and furniture, all I'll ever need.

    Then I priced 2x12 joists 20' long. I can make up my own beams from
    4-2x12's glued and nailed. I'd put in posts so I'll only span 7' with the beams. This chart:
    http://www.awc.org/calculators/span/...rcalcstyle.asp
    says I can span 19'11'' with 12''OC joists. All the charts for decks say I'm OK on joist span, but the made up beam spans all say 16' maximum joists can rest on the beams.This may include cantilever. If not I'll add more posts.

    The price for 2x12's is $784! Way cheaper. I'm going to have a carpenter and the lumber yard manager(our best friend) look at the whole final plan.

    I would rather use solid lumber. I know how to work with it. Framing the stair opening would be easier.

    The main downside is I'm close to the maximum span and the floor may feel bouncy. As long as it meets code I don't care. I'll use it for minimal storage. I mainly want it for the ceiling. It's hard to heat and light a shop with 26' high ceilings. The other downside is I can't find 12" wide insulation batts so may have to cut 24", but to save $1200? No problem.

    What would you do?
    Last edited by Andrew Joiner; 01-17-2009 at 10:30 PM.

  2. #2
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    My shop building uses I-joists and they are great. These are 22' joists, 16" tall and spaced 16" OC. While they may cost you a little more, the span they offer is just great. I-joists are also more forgiving when it comes to running wire and pipe through them in case that is a factor in your shop. They are also lighter to work with than big, long 2x12 boards, but yes, a little different. While was not around when the building was put up by a contractor for the previous owner, I don't have the impression that they are hard to work with.

    If you do have to go with the lumber and 12" OC, you can buy 24" insulation and just split the material down the center as you surmise.
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  3. #3
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    When you say I-Joist, are thost them things with a board on top and a board on bottom with a web of OSB in between?

    If so, I say run from them. The only reason I needed to hear to condemn them forever in my mind was: Firefighters. Should, god forbid, your place catch on fire, those webs are GONE shockingly fast. This leaves your entire span supported by a couple 2x3's. A solid 2x will actually smolder for a LONG time before it's structural integrity is compromised appreciably.

    If yer taklin' somethin' different, then ignore me. I dunno about scissor joists and such.
    Jason Beam
    Sacramento, CA

  4. #4
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    Quote Originally Posted by Andrew Joiner View Post
    The main downside is I'm close to the maximum span and the floor may feel bouncy. As long as it meets code I don't care. I'll use it for minimal storage. I mainly want it for the ceiling. It's hard to heat and light a shop with 26' high ceilings. The other downside is I can't find 12" wide insulation batts so may have to cut 24", but to save $1200? No problem.

    What would you do?
    If all you are using this space for is storage, then I'd just go with the 2x12's. The strenght of these is also determined by the species. Douglas Fir-Larch #2 is probably your best bet. They are a little pricyer than S-P-F, but they are much stronger and can span further.
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  5. #5
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    Yes, Jason.
    http://images.google.com/images?sour...-8&sa=N&tab=wi

    If they were cheaper I may use them and risk the fire weakness. I can see how you may be biased with your last name! Glad your not named skinnywimpysliversandglue?

  6. #6
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    Douglas Fir #2 and better is the grade. Around here it's all Doug Fir and the long stuff is usually 90% #1's. So it's good on the species.

    It may exceed the chart on spans,but the charts don't list all Doug Fir.

  7. #7
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    Just checked the AWC span chart and #1 Doug Fir-Larch spans 21' so that helps.

  8. #8
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    Quote Originally Posted by Jason Beam View Post
    When you say I-Joist, are thost them things with a board on top and a board on bottom with a web of OSB in between?

    If so, I say run from them. The only reason I needed to hear to condemn them forever in my mind was: Firefighters. Should, god forbid, your place catch on fire, those webs are GONE shockingly fast. This leaves your entire span supported by a couple 2x3's. A solid 2x will actually smolder for a LONG time before it's structural integrity is compromised appreciably.

    If yer taklin' somethin' different, then ignore me. I dunno about scissor joists and such.
    Jason,
    Do you have research to back up your statements above? I would say that I joists and are mostly used in commercial construction but are also used in residential construction moreso now-a-days. Someone may correct but i believe that the webs are not just osb which has been cut down.

    If there were that much of a problem with firefighters or fires I would think the firefighters would push to not be able to use them in construction at all.

    As to the OP's question. If you are only going to use the space as storage space I would go with the 2x12's if the capacity meets the spans you have planned out. If you are going to be using the space as occupied space I would consider the I-Joists because you will get a stiffer floor. A lot still depends on the spans etc. If you push the limits of the joists, either I-joists or lumber, you will have a bouncy floor.

    Another option would be to use the 2x material as joists but still use LVL's for your girders. I would have to see a plan to really get an understanding of what would be best. You have to decide if you want open space below or if you can stand more columns.

    One advantage of the engineered lumber is that they do work exactly like traditional lumber. Some of the hangers are a bit bigger...I think Jim hit the nail on the head that you can drill holes in the webs, make sure you follow the manuf. recommendations, to allow for pipes, cables etc.

    Greg

  9. #9
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    I have a google search ... it's enough for me.

    http://www.google.com/search?hl=en&q...=Google+Search

    I've heard firsthand from firefighters who've been injured due to a floor collapsing underneath them. It's fairly well known, as far as I can tell.

    I don't need more than that.
    Jason Beam
    Sacramento, CA

  10. #10
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    The fire fighting business is hazardous at times. A lot more houses are built around here with engineered I joists then any type of solid wood. If the fire gets to the point where it is starting to destroy the web I would have to say it is well along and the structure is already in big trouble.

    I am going to run it by a couple friends (who range from firefighter to chief) in a couple departments and see what they say.

    As for using them, they are easy to handle and install. If it is live load (you will be working in there) make sure you over size them and the beams. For just storage it isn't as bad since bounce isn't a problem.

    Span tables use different amounts depending on the amount of deflection allowable. I don't recall if it is i360 or l360 but that would be 1/360th of the span for deflection in the center. A 22 foot span with i360 is nearly 3/4" deflection. That would feel very springy under foot.

    Joe
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  11. #11
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    Quote Originally Posted by Greg Cuetara View Post

    Another option would be to use the 2x material as joists but still use LVL's for your girders. I would have to see a plan to really get an understanding of what would be best. You have to decide if you want open space below or if you can stand more columns.




    Greg
    Greg,
    My shop is built like a pole barn, but with 7-steel posts on a foundation for "poles".
    My site made beams made of 4-2x12's would span 14' between my existing steel posts that are in the side walls. The beams would be supported by blocking down to the foundation on each end and in the center.

    The 19' long 2x12 joists are supported on each end by these beams. There are no posts in the middle of the 19' span, so the first floor is all open.


    This is a tiny plan view. The x's are corner posts, the o's are center posts and the dashes are the 14' long beams. There's a large garage door opening on the right hand end.

    x---o---x
    o
    x---o---x

  12. #12
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    Andrew

    I would use the 2x12's with the cost differential being that great.
    I have to wonder though, exactly which engineered beams are you looking at? Some are just that, a beam, others already have the cutouts in them for DWV, Electrical, water, and HVAC so that they are just installed. The manufacturer has done the work for you. If you do end up with the engineered beams, remember that there are a lot of "rules" about cutting them.
    Maybe you were looking at more expensive beams that really didn't suit your purpose.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  13. #13
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    First off the paralams / microlams / and I joists DO NOT work like traditional lumber. They must be properly sized then installed exactly as specified by the manufacturer/ engineer using the correct hangers, nails and stiffeners all in the correct locations. Protecting them from flames included.

    Paralams / microlams - allow you to make headers and load bearing beams that would not be possible with standard lumber.

    I have used these in quite a few projects over the years -- not always to my liking.


    One example similar to yours:

    I rebuilt a old garage that inside was 22 feet wide and I wanted it to be open space with no poles holding up the floor. The garage had block walls and conventional framed roof with a floor support wall between the bays. We removed all the old ceiling/floor and supports and framed a new 2.4 wall inside the block wall to provide support for the new floor structure (the old floor was sitting on the blocks) I was using a contractor that I used previously with excellent results and I purchased all the materials from an authorized dealer who provided me the material and drawings. I was a disaster!

    Without going into all the details -- I had to rip out everything except the perimeter support walls and start over with a new contractor and my own engineer. I should have taken the roof off the garage and used engineered trusses -- it would have been cheaper and ultimately stronger!

    What I have learned is that 22' is a long way to go unsupported for wood products of any type -- you get a degree of sag and bounce with any structure that off times is not acceptable to many people using the area above. Since you are using this for storage it may or may matter to you at all - but be prepared.

    The floor above and the ceiling bellow MUST be glued to the I joist to stiffen the structure and all the rim support structure must be followed to the letter! The codes for deflection in a floor structure allow for so much deflection as to be IMO unusable for many uses.

    I have used I beams in other area for floors/ ceiling with fantastic results because you can get them in incredible lengths allowing you to quickly install a floor structure with no breaks plus the products are light and stable.

    Do continue your reading -- and think about paying a local engineer the very small cost of checking your numbers.

  14. #14
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    floor structure

    I would add to all the above...Whichever way you go, install a center blocking or even two rows of blocking between ALL joist. You wouldn't believe what a difference this will make in the bounciness of the floor. I personally feel the I joist will carry your span MUCH better than the 2x12 and will definately provide a more level floor. I have framed with both. I joists are simple to install. I'll also add that if you make your own beams, add a plywood piece in between the 2x12's. This will help to fir out to proper thickness and increase the stiffness a lot. Russ

  15. #15
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    http://www.raisedfloorliving.com/spantables-2.shtml

    If you check the link above and the link below it appears at first glance that the 2x12 and the I joist are similar in span but the above table (#1 grade sawn lumber) is l360 where as the below (I joist) is l480.

    http://www.trulinetruss.com/html/bod...s_-_ijoist.htm

    That is a difference of almost 3/16th's, .63 -vs- .475 flex in the middle.

    It is all going to depend on what you are doing upstairs. Bouncing floors are no fun to live or work on but for a storage area it is fine.

    I don't recall how much flex is OK before it starts to feel bouncy but it isn't much. You can also help with flexing if needed with extra briding, x braces and/or using plywood or OSB ceiling material underneath. Somewhere I have a book that gives a lot of info on joist flex but it is packed away somewhere that I can't remember.

    Joe
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