The term Wood Beam refers to a monolithic or composite piece of lumber engineered to span longer distances and support live, dead, wind, and seismic loads by transferring their weight to both ends and on down to a foundation. When a qualified professional selects a wood beam there are many variation and choice to be considered: structural grade, lumber species, allowable bending stress, allowable shear stress, modulus of elasticity, and minimum deflection permitted.
Rough Sawn Beam – A rough sawn beam is one whole piece of lumber cut to size. A common rule of thumb used for estimating the depth needed for a wood beam is the planned span/15. The width of the beam is commonly 1/3 to 1/2 of the beam depth. Deflection under full load should never exceed 1/360 of the total beam’s span.
Box Beam – A ‘Box Beam’ is a type of wood beam commonly used that is essentially a 2x box frame which is sheathed of plywood, and can span up to 90′
Built Up Beam – A Built Up Beam is a made up of 2 or more 2x pieces of lumber and is commonly considered equal in strength to the sum of it’s part’s strengths, as long as no splices exist. If two members are used, they are commonly nailed with 10d nails at 16″ centers staggered in rows. If three members are used, they are commonly nailed with 20d nails at 32″ centers staggered in rows.