Author Topic: Built-up beam question  (Read 7625 times)

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Offline Pa_Kettle

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Built-up beam question
« on: May 22, 2006, 04:04:01 PM »
The Little House plans call for (2) 4"x8"x24' beams for the 14'x24' house.

Due to cost and shipping issues, I would like to assemble "built-up" beams.  Would (2) sandwiched PT 2"x8"s be strong (or stiff) enough?  Or should I go with (3)? Or maybe (2) 2"x10"s?

I have read John's comments on placing 1/2" PT plywood in between the 2" boards to get the thickness dimension (3.5" actual) correct to sit on top of the 4x4 PT posts.  I have found sites that mention using PT plywood "spacers" instead of a continuous piece of plywood in the middle.  Which method is recommended?

Can someone post (or give a link for) explicit instructions for making these built-up beams?  I cannot find any good hits on Google about this.

What nailing pattern should I use?  Are screws better?  What size nails or screws?  What kind of glue?

I know I should stagger the joints by 4' and have them occur over posts.  I assume I don't want a joint at the outer post since that will leave a 2' part of the beam with no ability to cantilever correctly.

BTW, we are going to install the footings this weekend.  Woohoo!

Thanks,
PK

Offline PEG688

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Re: Built-up beam question
« Reply #1 on: May 22, 2006, 06:05:15 PM »
Quote

  
 #1   Would (2) sandwiched PT 2"x8"s be strong (or stiff) enough?

  #2  I have read John's comments on placing 1/2" PT plywood in between the 2" boards to get the thickness dimension (3.5" actual) correct to sit on top of the 4x4 PT posts.

   #3   Can someone post (or give a link for) explicit instructions for making these built-up beams?

     #4  What nailing pattern should I use?

     #5 Are screws better?

     #6   What size nails or screws?

      #7    What kind of glue?

      #8    I know I should stagger the joints by 4' and have them occur over posts.


        #9    I assume I don't want a joint at the outer post since that will leave a 2' part of the beam with no ability to cantilever correctly.

      #10     BTW, we are going to install the footings this weekend.  Woohoo!

Thanks,
PK


  #1  If your piers are 4' OC 2x8 dbl should be good.

  #2  Yup , 1/2 plywood spacers 3 or 4 " wide 7" long every 16 " OC . I do not have John's plans if he spec's PT for the joist and the under side of the cabin / building will not be closed in with skirting to make it sort of like a crwl space PT 2 bys and spacers might be wise. I wouldn 't stress on the ply being PT if it where me  ;)

 #3 Stager your joints, you should only have 3 per beam . Put the joints over a post.

 #4 I'd go three , two , three about 16" between the 3 nails center on that to the two.

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     Best I can do for graphics  ;D

  #5  No unless they are graded. Not  as much shear in most screws .

  #6 16d Galv nail,  angled so they don't stick out when driven.

  #7  Const . Adh. like you'll use for the subflooring , optional IMO, not required.

 #8  Roger :)

 #9  Your joints should be 6' back from the end of a 24' beam  use 12',  12' = 24' one side , 6' , 12' ,  6' = 24' other lamination.  One beam takes 4 / 12'  2x8's .

 #10 OUTSTANDING , good luck, PEG

  
« Last Edit: May 22, 2006, 06:07:41 PM by peg_688 »
When in doubt , build it stout with something you know about .


Offline Pa_Kettle

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Re: Built-up beam question
« Reply #2 on: May 22, 2006, 06:37:51 PM »
WOW!  Thanks PEG688!

Just to be sure, I'm nailing the 7" plywood strips vertically, with 3 nails, moving horizontally 8" inches and nailing another 7" strip with two nails.  Rinse lather and repeat, correct?  Are my angled nails parallel with the ground (rotated looking from above) or diving up and down or both or does it matter?  ;D

PK

P.S. I just re-read your response which states the plywood spacers are 16" OC.  So am I not putting a spacer where the 2 nails go, or are my 2 nails 16" OC from my 3 nails?   :o
« Last Edit: May 22, 2006, 06:44:34 PM by Pa_Kettle »

Offline PEG688

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Re: Built-up beam question
« Reply #3 on: May 22, 2006, 07:04:41 PM »
I sort of eye ball the spacers in you won't pull the 2 by in "to much" with the spacers just at the 3 nail line . but if you want you can put the spacer between the 2 bys at all the nail lines , They are really just spacers the dbl 2x8 do the "carrying "/ support.

 The angle of the nail is just so they won't poke thru and stick ya when your carring them / climbing over / pulling wire etc , angle what ever way make it easier for you to nail.

  7" long is a lil shorter than a 2x8 , they should measure 7 3/8 , or 7 1/4 "  so the 7 " ish strips also will not stick up or down but be inside the sandwich never to catch / hold up / get in the way again :)

  As your nailing that beam together it helps to work from one end  to the other. Having a helper move the top peice left or right to line up the top , crown the 2 bys first , crown up , tack on the spacers with angled 8's or 1" roofing nails .
 Try to keep the top of the beam flush ist as your joist will sit on it .


     If you can build it (The beam )  on horses right next to the posts and you have the help you might be able to build it all flat and rotate it down right on to the post put one gusset on the posts to help guide it . This might be into TMI (To Much Info) and only confuse you . If so delete your mind back to what you understood and start over,  I , TMI ,  my guys at work some times as well and when I  see the "glazed over" look I stop  ;D

  Good luck , PEG
    
« Last Edit: May 22, 2006, 07:34:20 PM by peg_688 »
When in doubt , build it stout with something you know about .

Offline glenn kangiser

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Re: Built-up beam question
« Reply #4 on: May 22, 2006, 07:23:29 PM »
There you have it from the pro, PK.  PEG's always a great help.
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

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Offline John Raabe

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Re: Built-up beam question
« Reply #5 on: May 23, 2006, 06:52:47 AM »
Again, just super work guys!  ::)

My quote at the bottom couldn't be more true. It is great to have the support of folks like PEG who know how to make a drawing into a physical reality.

This is wisdom and experience you will never be able to get written out in a set of plans.
None of us are as smart as all of us.

Offline Pa_Kettle

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Re: Built-up beam question
« Reply #6 on: June 01, 2006, 05:55:20 PM »
Whoops!  In reviewing the Little House plans I noticed the information I was originally seeking is on the first page!  :-[

Anyhoooo,  we've got the footings backfilled and the deck blocks in.  I'll post to the owner building forums when I've got a bit more progress to show.

Thanks,

PK

 

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