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structural ridge beam lvl
my architech speicfied a structural ridge beam for my home addition. he will be using a 24' long x 5 1/4" thick x 14" deep 2.0e lvl. the roof load will be 30live/15dead. the room span is 20' i am concerned that this beam may sag over time as it is a 24' free span. can someone framiliar with glu lams give me there thoughts on this design.
thank you.
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glulams can be selected from a load table. you might want to ask them if there is a benefit to chosing the next larger, you might want to have him double check that all loads were on the high side, and you might ask him if he would specify something else if cost wasn't a consideration.
loads have a lot to do with climate. there are wind and snow loads. where are you located?
are the supporting columns adequate? if you are having doubt about the beam, what about the supports?
a 14 inch beam for a 24 foot span is probably marginal if deflection is a concern. the international paper catalog for 2.0e lvl engineered beams does show 16 & 18 inch depths available. one of these may be a better choice.
do keep in mind that any beam (wood, steel, it does not matter) will "sag" - it is working like a giant spring to carry the load. however your roof will be "seeing" the dead load only, most of the time (unless you have a lot of snow). live load capability will be required typically for times of high wind.
one way to address this subject with your architect is to ask for a total load (not just live load) deflection limit of 1/240; this will probably force him/her to select a deeper beam.

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