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

  1. #31
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    Quote Originally Posted by Anthony Smaldone View Post
    I'm a Lieutenant in the FDNY. Let me say, if we were able to, we would ban Wood I joists from ever being made. They fail within min. of being exposed to fire. They are very dangerous to the fire Depts. throughtout this country. Main reason being, We do not know which buildings have them and which do not. They have killed and will continue to kill us.
    Anthony,
    Are Wood I joists banned in NFPA? Is this something that NFPA is trying to do right now? It sounds like the problems are with the OSB. Is that correct? If OSB is that much of a problem are there any issues with using OSB for roofing and flooring rather than regular plywood? I would think roofs made with OSB might go up in flames faster and make it even more dangerous....yet another reason in my mind to use real plywood as a roofing material. Is it just the I joists which have the OSB web which are a problem? I know they also make I joists with tubing as the webs or 2x material for the webs. Should OSB be banned altogether?

  2. #32
    Quote Originally Posted by Jason Roehl View Post
    One thing I haven't seen yet in this discussion is the difference in feel between the two floors. An I-joist floor can be made very stiff (low deflection), but will still bounce due to the lack of mass--it will vibrate for some time after all motion on it has ceased. Solid lumber has more mass, but is more flexible, so it takes a much larger 2x to achieve the same lower deflection as an I-joist. Due to the higher mass, however, vibrations are dampened.

    If someone has a china cabinet in their dining room, I can probably tell how the floor is constructed just by walking through the center.
    Good point. I recently added a second floor in a barn using BCI at 24oc, and 3/4 edge gold. I have a laser level and had it set up to check the ceiling heights, when I walked through the room, the laser went crazy. I hadnt realized before how much vibration was in a floor system.

  3. #33
    Join Date
    Jan 2009
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    Pine Falls, MB, Canada
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    Like Allen said, thanks for thinking of the firefighters. I am Deputy Chief of a small department and we have many homes that have been built in our area in the last 10 years and I can't think of one that used dimensional lumber. When I built my home this summer I used iJoists. You need to follow the manufacturers recommendations in terms of protecting the joists from direct flame contact. This is where most people fail as in almost every home people finish the main floor and leave the basement until a later date. I finished my basement immediately. I drywalled my basement ceiling with 5/8 firegaurd which gives the ijoists added protection. I've attached a couple of pictures that we use in training new firefighters. The story behind the pics is that there was fire in a home under construction. Fire started in a construction heater and was contained to a limited area in the basement. Very little fire extension past the basement level. However the engineered joists were exposed. FD was on scene within 6 minutes and made entry 8 minutes from initial call out. The destruction of joists compared to the damage in the remainder of the house is incredible.

    Hope this helps.
    Attached Images Attached Images
    Last edited by Kerry Medeiros; 01-21-2009 at 11:53 AM. Reason: typo

  4. #34
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    Sep 2007
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    Burlington, VT
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    Thanks for all of the info. As a designer I have been spec'ing TJI's for a few years now. As others have pointed out, it is hard to get decent 2x material anymore. I do like the fact that they are easy to work with and they are a very consistent product. I had not realized the fire implications but I will take note now to ensure proper fire protection is spec'd. I think this is consistent with many new products. For instance I see more and more projects that use spray foam as the insulation since it has so many advantages over other systems but the fire risk is also greater. As such the foam must be properly protected.

    Another thing to consider in using the I joists is that there are often 2 span tables in the literature. In larger houses I do not rely on the span tables and instead I use a structural engineer to size the joists. The engineer is always very specific with the client regarding how much "bounce" is acceptable to them even when we are framing with dimensional lumber. In smaller projects I will use the span table showing the L/480 deflection instead of the L/360 which will result in a stiffer floor. L/360 is the minimum allowed by code and who wants a house that just barely meets the minimum legal requirements. I am doing this in my parents house now and those floors are rock solid! And finally I never let the lumber yard/manufacturer run the calcs on a house. If you notice they usually put some "weasel" words in the documents regarding the fact that everything is sized for the average span. By definition some of your spans will be greater and some less than the average. You can end up with some really solid areas and one or two bouncy areas.

    Anyways, I don't think the I joists are going away any time soon. Like many "new" products they have advantages and disadvantages and it is up to architects, designers, engineers, and builders to work to make sure that the products are used correctly. I am telling my parents tonight to make sure the basement ceiling gets a layer of sheetrock as it is the only area where the TJI's won't be protected.

    chris

  5. #35
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    Wow Kerry! Those photos are amazing. As an architect I find them really interesting, and will log those in the old memory for later. I usually don't spec, TJI's around here, but from now on, I'll make sure to add the fire-rated gyp board with notation on my drawings.

    And Chris, make sure your parents use the fire-rated sheetrock, just like the attached garage (if there is one).
    It’s only work if somebody makes you do it.
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  6. #36
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    I used to be a Maryland volunteer firefighter in the 1990's

    In all of our firefighting classes they drilled into us the problems of the composite floor systems, particularly the wooden I-Joists. They must be protected from flame impingement, drywall being the most common UL rated fire barrier. Also, when sealing gaps/holes for utilities that could cause flame spread, (from wall cavities etc) make sure to use fire-rated sealants. The normal "great stuff" is not fire rated. However, they do sell one that is.

    Francis Brannigan is considered the guru of fire and building construction. His books are considered the firefighter's bible.

    Even the Wooden I-Joist manufacturers association (WIJMA) caution about the Fire problem. And have a handy video on thier website.
    WIJMA has taken a proactive stance on the issue of fire safety. A 10-minute informational video for fire fighters has been developed to address many fire issues related to modern construction.

    Significant additional information on life safety risk to firefighters and occupants is needed. WIJMA is currently working with organizations such as AF&PA and CWC to address common fire performance issues across the engineered wood products industry.
    ~~~~~~~~~~~~
    The fire issue aside.

    To compensate for the other shortcoming of the springingess and deflection, Wood I Joists offer a solution.
    The one advantage that no one mentioned about the wood I joist is its easier to get stiffer material, just needs to be taller. I think I remember Bruce Hoadley's "Understanding Wood" discussed that 2 2x8 was similar to one 2x10 in strength. So a taller joist makes a better floor, and you might consider that if you are splitting a 26' floor to ceiling height.
    The original manufacturer Structural Wood Corporation has a handy table of sizes they make.

    ~~~~~~~~~~~

    In the issue of cheap and frugal, you might check if your local metal shop has any un-used steel bar joists, leftover from a job. (ordered wrong size, cancelled job etc.) If so, you could have them modify them (with engineer's calculation/drawings). I would bet they would part with them for a reduced cost, otherwise they would only get scrap metal value. You can screw or powder actuated fastener a plywood deck to the joist. Not sure if that would be cheaper, just an option.
    The wisest thing in the world is to cry out before you are hurt.

    Board-Stretcher 101 : I cut it twice and it's still too short. I don't understand?

  7. #37
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    Kerry's post made a believer out of me. If ya gotta use it cap it with fireguard sheetrock ASAP.
    David B

  8. Floor trusses, I-beams and solid dimensional lumber

    First a little about me. I owned a roof and floor truss plant for 25 years and sold a lot of I-beams. Also built pole buildings, steel buildings and high end homes. Now I am doing honey-does for my wife. Of all the things I did I loved to build heavy timber trusses with 1/2 thick steel connectors plates.

    I agree with most of the previous responses.

    Lets talk about span, it is difficult to get solid lumber over 20 feet. So a room clear span assuming 6 inch walls would only be 19 feet wide. This does not make a lot of architects happy with dreams of large flowing spaces. First there was floor trusses and them I-beams. These usually went into cost competitive townhouses and homes.

    Of course you could use heavy laminated wooden beams and then ladder in-between with 12"s for example. This works but is costly and creates a thick area between the ceiling of the first floor and the floor of the second floor. In some cases it could be 2 to 3 feet thick. And the beam might project into the room below creating a non flat ceiling.

    I-beams are cheaper than floor trusses. I-beams are generic extruded item.

    The floor trusses are custom manufactured to a height and length.

    I-beams require end blocks to prevent crush of the product. Installed on site.

    Floor trusses are faster to install.

    The higher the floor truss or I-beam the stronger it becomes. This is very important. It is cheaper in general to have a higher truss than more lower height trusses spaced closer together.

    The added height of the I-beam is not very expensive.

    I-beams come with 2x2 and 2x3 and 2x4 tops and bottoms. The reason to have different size chords is just cost. What a giant builder wants is JUST to make code. Nothing extra. Cost drives the construction market.

    I have a garage that is 30 foot clear span and has 23 inch thick ( high) floor trusses. 12 inch on center with two layers of 3/4 subfloor and 3/4 inch of 5 inch brazilian cherry.

    There is no bounce and the room is very solid.

    You can have your local building supply( forget the big box stores) and get a

    recommendation on sizing. However give them some design information.

    Size of bearing----such as a 2x6 is 5 1/2 inch on both ends.

    span----------------inside distance from bearing to bearing

    load----------------what is on top-----equals top chord load
    what is on the bottom-----usually sheetrock
    what is the live load-------people, machines, furniture , file cabinets filled with "stuff". The biggest problems I had was from accountants, lawyers, national geographic collectors who had lots of concentrated loads, water beds , full size snooker tables 6x12 with 2 inches of slate.

    So tell the man what you are doing.

    Usual bedroom load is about 55 total PSF

    commercial loads run from 100 to 250 and up.

    The room over my garage was designed for 300 pounds PSF with almost no deflection and no apparent bounce.

    Nice thing about I-beams is that they are easy to install. Floor trusses usually are designed NOT to be cut. So the builders must build square straight walls.

    I-beams are easy to use in tapering conditions. That is where walls are not parallel.

    In the past we built roof trusses to 80 foot and floor trusses to 40 foot. These are all clearspan. We built some trusses for the navy that closed two tunnels and we had state police escorts for 150 miles closing the bridges.

    It only cost money and you can get anything you want.

    If I was looking for a large room with clear span area. For example 40x60

    Get some used big steel I-beams 40 footers (tall in height) say 3 of them and then ladder them with tall I-beams or floor trusses. If you find 4 steel I beams you could ladder with solid lumber. Years ago I got a steel Ibeam from a old railroad bridge. 44 feet long 24 inches thick and about a little over 300 pounds a foot. It cost me under 500 dollars delivered. That thing weighed over 13,000 pounds and then a crane and welder to cut the beam. But I have a room roughly 44 x 58 in the basement.

    You local building supply can help you and then take it to a structural engineer for review and suggestions.

    Also remember to build big footers. I like like the german concept of 36 inches wide x18 inches thick and 4 pieces of 5/8 rebar. I have always used 5000 psi concrete for the last 30 years. Overbuilt yes for sure, but you can sleep at night. ( actually it is 1 meter by half meter).

    Sorry for the rambling.

    Herb

    Ps. I built a gym for a church. The design was simple they wanted 120 wide and 200 feet long. Low height to be 24 feet and 40 foot clear in the center. No columns anywhere. get what you want try not to settle.
    -

  9. #39
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    Wow, GREAT information here. You guys are reading my Mind! Now retired, I want to build a 32x32 dream shop/garage in what space I have out back. I have more Time than Money and wish to do as much as possible to save on cost and pay as I go,

    The building will cost more to *look nice* (same siding/roofing/2nd story) because it is adjacent to my home. Otherwise I would just throw up a big metal building if I had land! I am not so blessed. Since extra $ must be spent on appearance I want to save wherever else I can, without compromising structural integrity. These are my ideas so far:

    * 4" concrete slab floor

    * 2x6x10' walls, 16 or 24"" centers?

    * gambrel roof w/ 2nd floor for storage of heavy stuff i.e. hardwood lumber, machinery, (for now) but roughed in for toilet and electric for future efficiency apartment.

    * upper floor supported by longitudinal homemade lam-beam, in 3 sections, 4-1/2x16x10'4" (made of 6 lams 3/4 OSB using plastic resin glue, lam butt joints staggered by 24"

    * 3 Lam beam sections bolted together 1/4"x16x24" steel gusset plates, supported on 2 posts (4" heavy wall pipe with welded steel 3/8" top plates.

    * Homemade I-beam floor joists (12"x16ft on 12" centers) 2 lams 3/8" OSB, butt joints staggered 24", 1-1/2"x1-1/2" top/bottom chords, plastic resin glue. (can I-beam halves be joined over center beam support?)

    How am I doing so far?? After reading here, I do not think I am too far off. I appreciate any professional advice anyone can afford. Main concerns are with building my own structurally sound Lam center beam and I-beams as indicated? I am not naive, but believe much can be done to save money if the right materials and techniques are used when my time is FREE!

    P.S. Certainly not my intention to hi-jack this thread! I guess I got carried away! I think I am right on track as the OP with same issues., with the DIY aspect.
    Last edited by Chip Lindley; 01-23-2009 at 11:45 AM. Reason: apology if hijacking
    [/SIGPIC]Necessisity is the Mother of Invention, But If it Ain't Broke don't Fix It !!

  10. #40
    Join Date
    Apr 2008
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    Manassas VA
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    The other way to build strength into a wood joist is to sandwich in a steel plate (or two), called a flitch plate.

    This is often done for garage door headers because of the long span and loads



    Commercial sources for a pre-assembly:
    http://www.betterheader.com/
    http://www.readyheader.net/

    Engineering info: http://www.structuremag.org/Archives...ac-5-10-07.pdf

    If you want to make it yourself, go to the local steel shop and order a flitch plate. They can punch or drill the large holes quick and cheap. You need open span length +2 bearing sides. Normal maximum length is 20', longer will require splicing plates. Buy it undersized in height, example 9" wide plate for 2x10, 11" for 2x12. Thickness depends on strength needed, however going over 1/2" thick means it won't be flush in a 2x4 wall.

    Typically a local steel shop will charge by the pound, expect about $ .75 to 1.25 per lb depending on raw steel prices (it is coming down now).
    The wisest thing in the world is to cry out before you are hurt.

    Board-Stretcher 101 : I cut it twice and it's still too short. I don't understand?

  11. #41

    My "Garaj Mahal"

    Quote Originally Posted by Herbert Mulqueen View Post
    I have a garage that is 30 foot clear span and has 23 inch thick ( high) floor trusses. 12 inch on center with two layers of 3/4 subfloor and 3/4 inch of 5 inch brazilian cherry.

    There is no bounce and the room is very solid.
    <snip>

    The room over my garage was designed for 300 pounds PSF with almost no deflection and no apparent bounce.
    No bounce? I should hope not! That's a floor system on steroids!

    My shop has considerably less beef and has a 28' span (outside to outside). I used TJI joists 16" O.C. with a single layer 3/4" t&g plywood floor, glued and screwed. If memory serves, my joists are 18" high with 2x4 chords.

    My shop is over a 3 1/2 car garage. I didn't want any columns in the garage, so I ended up using TJI joists due to cost and ease of installation. Most of the joists were installed by just me, my FIL (who was in his 70's at the time) and my "skycrane". The crane is mounted to my truck in the pic's, but it was reworked onto a big dolly to hang the roof trusses later.

    I have a single row of blocking run down the center. I built the blocking using 2x4's, slightly oversized and trimmed each one to fit snug.

    My floor is quite sturdy and I'm very happy with the results. I did not consider fire implications of the TJI joists, and I appreciate knowing that I should drywall the ceiling when money permits.

    The building inspector was impressed with the solid feel of the floor when he did the final inspection.

    I attached a picture of my blocking, taken while I was building them. I shamelessly copied the design from one found on the internet.

    Close inspection of the garage door headers will reveal they are Flitch plate construction. I went with 12" tall, 1/2" thick mild steel. The supplier punched the holes for the bolts. I notched the studs to accomodate the fact that the steel was 1/2" proud of the 2x12's.

    I really enjoyed building my garage/shop and like to refer to it as the "Garaj Mahal". LOL!

    Fun stuff! Good luck with your project.

    Dave
    Attached Images Attached Images
    Last edited by Dave Zeigler; 01-23-2009 at 4:44 PM. Reason: fixed typo.

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