Replies

1. 
   CAGIV | Nov 25, 2002 09:59am | #1

   It depends on a lot of unknowns, such as what type and how much load is it going to carry, and the type of wood being used for starters. In a chart that I have it recommends roughly a 4"x16" beam of strong wood, I don't know how accurate this so I wouldn't quote me, but it might help get your thread going.

   Incidentally I might recommend an engineered beam, they are stronger, can be smaller then a solid wood beam, and are more stable, they wont expand and contract as much as a solid wood beam.

   Anyway, like I said, not going to guarantee what I said above, just out of a chart in a carpentry book I have

   Good Luck

1. 
   fdampier5 | Nov 25, 2002 06:48pm | #3

   Cag,

     I'm sorry my friend but I have to disagree with you strongly for the following reasons.

        1.   Engineered wood has not stood the test of time that timberframing has. 

        2.    The net cost of wood to someone who owns his woodmizer is real close to pennies compared to how many dollars for engineered wood?

        3.  When is the last time someone looked up in awe of a engineered wood beam?

       Just for starters...

       As for the original poster,  If you can share some of the details I can help you figure your options.

     I need to know the type of load and if it's in one spot or spread out.  I'll need to know the type of wood (I'll assume the wood is green, not dried) and finally I'll need to know how you will connect it. (nails, pegs, mortice & tenion, etc.)

1. 
   CAGIV | Nov 25, 2002 10:37pm | #6

   Frenchy, between this post and the one on sips I'm starting to think your not a big fan of engineered beams lol

1. 
   fdampier5 | Nov 26, 2002 02:59am | #8

   Now what makes you think that?  ;-)

      Actually I tend to be way to impractical about things that I like.  I need to remind myself that not everyone can get wood as cheaply as I can or spend all the time it takes to build their own house.   Besides I'd be willing to bet that if everyone built things my way , I'd stop and do it differantly!!!!!      ;-)

1. 
   CAGIV | Nov 26, 2002 08:01am | #10

   Frenchy, just the impression I got :)

2. 
   Ragnar17 | Nov 25, 2002 10:20pm | #4

   Cag,

   Not to beat up on you, but I have to agree with Frenchy on this one.

   Isn't the whole point of timber framing to showcase the natural beauty of wood?   Maybe we can salvage your suggestion by adding a caveat: could an engineered wood (or even steel) beam be hidden inside an attractive wood box beam?

   Hope I'm not hijacking the thread here.... the original question was just about sizing the beam.  <g>  Regarding that question, more data is definitely required.

   Ragnar

1. 
   CAGIV | Nov 25, 2002 10:32pm | #5

   I'm not saying and engineered beam would look great, and I never said anything about it being cost effective over a person being able to mill their own beam, and no it hasn't quite stood the test time, I just meant it as a suggestion.

   Was  my statement incorrect that an engineered beam would be more stable then a green beam and could also be substantially smaller?

1. 
   Ragnar17 | Nov 26, 2002 01:17am | #7

   CAG, 

   From the latest spec sheet I’ve had in front of me, allowable stress in PSL beams is 2900 psi in bending, whereas #1 Doug fir is about 1300 psi.

    If we take, as example, the 4x16 (3.5” x 15.25”) over a 22-foot span, and assume uniform loading of 20 pounds per lineal inch, the resultant bending stress at midspan is 1284 psi.

   By comparison, a PSL beam could handle the same loading with a cross section of only 3.00” x 11.25”, with a resultant bending stress of 2753 psi at midspan.

   This example is just for fun --- I’m not sure what sort of allowable stresses can be used with green timber, and I certainly have no information regarding the actual loading of the beam in question.  That said, the example shows that you could get by with a smaller PSL beam.

   Would it be cheaper?  I don’t know - those PSLs are kinda spendy as I recall.  I also share your concern that the PSL beam doesn’t have the same track record as wood since PSLs haven’t been used for 6000 years.

   Regards,

   Ragnar

    

    

    

    

1. 
   CAGIV | Nov 26, 2002 03:22am | #9

   expensive they are and thanks for the info.

2. 
   NPitz | Nov 25, 2002 02:01pm | #2

   It depends entirely on the the load to be supported, and whether it is a uniform load or not. Tedd Benson's book "Building the Timber Frame House" has a section in the back with fairly detailed information on beam sizing based on wood species, span, and loading. My recommendation would be to buy the book. The way the tables are set up is very handy because they allow you to compare different size (beam width versus height) beams for the same application.

3. 
   Piffin | Nov 28, 2002 08:24pm | #11

   So, to sum it all up, Your friend needs a book as much as a chart, to know how to size a beam.

   .

   Excellence is its own reward!

   "The first rule is to keep an untroubled spirit.

   The second is to look things in the face and know them for what they are."

   --Marcus Aurelius