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Question
will 4x8 cedar rafters spaced 4 feet apart span 15 feet and support (w/o sagging) an aluminum cover that weighs 1.5 lbs. per sq. ft. I live in south teas where we rarely see snow.
Hi Jeff, if you put the crown side up you might be okay but 15 feet is a long span for a 4x8 even without any load applied to it. Rule of thumb is one inch of thickness for each foot of span using 4x material..so a 4x15 would be the recommended beam size under optimal conditions. but you can usually cheat on that rule of thumb by a couple of feet...there are several beam sizing charts available online also..
check this one out from AceHardware..http://www.acehardware.com/info/index.jsp?categoryId=1283461
As you can see from this chart a 4x10 beam will span up to 12 feet..I hope this information helps please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com
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Answers by Expert:
Bruce E. Johnson
Expertise
I can answer any construction related question in regards to carpentry, concrete, drywall, masonry, structural elements of any type of building, residential or commercial. Interior or exterior.
Experience
Custom Commercial and residential buildings. Churches, theaters, schools and auditoriums. Most recently I am working with the Catholic Church on several design build committees. I have a website related to scheduling and project supervision. Although my expertise is more related to multimillion dollar commercial, educational and theatrical projects my generous credentials in residential and remodelling construction make me a viable source of information regarding all forms of building questions.
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