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Plywood box beams

inperfectionist | Posted in Construction Techniques on September 10, 2008 01:21am

Years ago, while working for a GC, we did a building w several plywood box beams for headers. I was young at the time, but it seemed like a great idea,,,,,very strong, simple, site built beams. I recall the building coming out very well.

Anyway, question is, are they very common now-a-days?

I can’t recall ever seeing any reference to them here on BT.

Has anyone here built any lately? Is there a situation when they are commonly used? Is there a disadvantage to them?

I was reading a piece on the APA web site,,, seems pretty straight forward to size and build them.

I don’t know how most BI would react to seeing them.

Thanks, Harry

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Replies

  1. Danno | Sep 10, 2008 02:33am | #1

    I haven't seen them done even back when I did framing in '96. Seems like a good idea though. Maybe they are unusual enough that building inspectors don't like them.

  2. oops | Sep 10, 2008 02:34am | #2

    Harry.

    They are not common in my area.

    I have not seen anything, but I have not been looking.

    I have not done any recently. Used  them back in the 60's when in the prefab business. My guess is that most framers had rather not fool with them.

    Since they are an engineered item, the BI could want a PE stamp/inspection. Most BI's don't like anything that is different from the norm. Then neither do most GC's.

    I always thought that  kind of stuff was fun, but I'm not sure how good one can control the quality on a job site. We used a nail and glue system and was fabricated inside a building.

  3. junkhound | Sep 10, 2008 02:40am | #3

    I designed a 30 foot 3 ft deep pw box beam for my brothers house - 3 ea 2x6 on each chord, held up 1/2 of the 2nd floor and 1/2 of the roof. OK service now for about 20 years with no sag.

    Brother told me that if he had known how much work it would be to build it even though the materials were low priced (1/3 the cost of a glu-lam), he would have gone with the glulam even though he would have had to rent a crane to place it.

     

    1. inperfectionist | Sep 10, 2008 03:19am | #4

      I guess w the availability of the engineered beams now, there no need to be making your own.The place I refered to that we built back when was on a little island.
      Maybe thats why we built those beams.At the time, it was a real good lesson to a young guy about a structure being stronger than the sum of it's parts.H

    2. oops | Sep 10, 2008 07:02am | #12

      Your post brought back lots of memories. I hate to do this to you guys. I always hated it when my dad use to tell me about how he had to walk to school in the snow and had no shoes. But here goes.

      When I started designing plywood box beams, there was no such thing as a calculator.  You used a slide rule and lots of paper, #2 pencils and a big eraser. Back then it was DFPA (Douglas fir plywood association) not APA (American plywood association). That was before yellow pine plywood. The pages are all yellowed now, but I still have my old "Fir Plywood Technical Data Handbook" dated March 1959. Man, It was a lot of work back in them old days. Box beams and stressed skin panels was cutting edge technology. We did some neat A-frames (24' x 36') made with stressed skin panels. 4' wide x 24' long panels. Last time I checked, they were still standing  on the side of a mountain just west of Los Alamos NM  Won't bore you with all the construction details. It was fun though.

      After looking at your profile, I figured that your your 3 score plus years would make you a little more understanding. Good looking pics. You got it right about the amount of labor. We were able to get them in the dry in one day.

  4. cargin | Sep 10, 2008 03:50am | #5

    imperfect

    Here is the APA site on box beams if anyone is interested.

    http://www.apawood.org/pdfs/managed/Z416.pdf?CFID=6909442&CFTOKEN=31910354

    Rich

     

    1. inperfectionist | Sep 10, 2008 04:04am | #6

      Thanks,I was reading that site last night,,,, thats what got me thinking.

      1. Clewless1 | Sep 10, 2008 01:06pm | #14

        I was going to say ... sure ... they are a great idea ... with the downside that you might have to have them engineered/stamped for the BI to accept them. But maybe the APA website has some stock design tables (looks like it) that can be used. NICE RESOURCE!! the other poster offered us!! WOW! Nice.

        I've often thought this is an underutilized resource (site built beams). Ive often thought about turning entire walls into deep truss/beams that span a large space below (e.g. a bearing wall going across the middle of a garage). Design the openings into it, glue and screw sheathing to it ... voila ...     Can a standard truss guy do something like that, I wonder?

        Downside that I can think of is that if you construct w/ it and you go through a rainy period, it MAY not be a good thing (or acceptable). Could always drape some sheet plastic or something over it and then cut it away when you are dried in.

  5. MikeSmith | Sep 10, 2008 04:06am | #7

    we always build plywood box headers...  really like the extra insulation

    here's a link

    http://forums.taunton.com/tp-breaktime/messages?msg=92880.50

    Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
    1. inperfectionist | Sep 10, 2008 04:25am | #8

      Mike,That's a great modern use for the plywood box beam! I take it your inspector is OK w them.That RFH Ranch was a great blog,,,,I must have missed the headers the first time around.We need to get a collection going here,,,, puchase a lot,,,, get you guys buiding another house.Harry

      1. MikeSmith | Sep 10, 2008 04:30am | #9

        i got them right out of the code book...... IRCMike Hussein Smith Rhode Island : Design / Build / Repair / Restore

  6. Jim_Allen | Sep 10, 2008 06:29am | #10

    I remember the good old days of box beams. In my first construction job, (I worked in a steel supply shop), I was a utility truck driver and one of my jobs was to run the boom truck. I remember setting a bunch of those box beams on a job once but I've never built, nor used one myself.
    I think I did learn about them in carpenter school too..but not too much about them.

    1. Jim_Allen | Sep 10, 2008 06:33am | #11

      Now you made me take a walk down memory lane when things were simpler. Back then, if I wanted to be a truck driver, I had to get a chauffer's license. It cost an extra $5 per year more than a normal license. I had to answer ten questions...stuff about maximum length, flags etc. So, with my $5 license, one day, they put me in a semi even though I had never drove one...and away I went.

  7. joeh | Sep 10, 2008 07:26am | #13

    IRC 2000 covers them.

    Joe H

  8. user-144854 | Sep 10, 2008 03:13pm | #15

    I've done them in situations where I was the only carpenter and heavy lifting was impractical -- just assembled them in place.  Those jobs were generally remote cabins or other scenarios where inspections were not involved, but I've shown the B.I. my calcs a couple of times and they've been OK with it.  An inspector is within his authority to question quality assurance, so it can be a matter of gaining his confidence or being prepared for tear-out.

    }}}}

  9. fingersandtoes | Sep 10, 2008 09:01pm | #16

    The only downside I can think of with box beams is that because they are uncommon and don't look like a beam, people working on the house in the future might not recognize them as a load bearing part of the structure. 

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