Expert: Bruce E. Johnson - 5/18/2010

Question
Aloha Bruce,
Is there a chart that is used in carpentry framing to determine header beam sizes for different spans on single level homes?? Example- 4x6 used up to 4' span, 4x8 up to 6' span etc?? My specific questions is for a 14'span and 20'span? Thank you for all you do and your expertise is appreciated here in Hawaii!!
Aloha , mike g.

Answer
Aloha mike g.,  I am sending you a link on how to calculate header sizes.  It's a little tutorial but if you follow the steps you should get the information you need.  www.awc.org/technical/spantables/tutorial.htm
One rule of thumb for headers and beams is one inch of height per foot of span in 4" material..i.e. 4' span 4x4, 6' span 4x6, 12' span 4x12..etc.  Once you get over 12 feet it gets a little iffy after that because of lumber sizing and the availability of heavier beams.  We have been using laminated beams (LVL's) for longer spans lately.  They don't have to be as thick as nominal lumber and you can get them in any length. They come in 1 3/4" thicknesses and we double them up to make the 3 1/2" thickness for standard 2x4 wall framing.  An LVL to span 14' is generally 11 1/4" high and to span 20' is 16"..to inquire about LVL's you can contact your local lumber yard or truss manufacturing company.  They can give you specific engineering guidelines for your needs.  I hope this information helps, please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com