Expert: Bruce E. Johnson - 9/21/2008

Question
QUESTION: hello Bruce!!!
i have a 28ft wide x 16 ft long patio. 28ft along back of the house. i have footings on the front of it already in there when i did the concrete. footing are 3x3x4 at each end on the 28 feet width. i want to build a covered roof attached to the house and on the 2 footing i would like to have the 2 fiberglass columns. is 2x6 ok for the roof? i was thinking of fabricating a beam with 2x10  or 2x12 for the 28 feet span. i don't have footing in the middle. should i build a beam with wood? get a steel i beam? i prefer to build it with wood because i don't know how heavy the steel beam will be. can you help me out? wood or steel  and what size steel or 2x?
i live in south new jersey so what is the minimum pitch of that roof. and are 2x6  ok for it?
thank you very much Bruce!!!

ANSWER: Hi Jimmy, I don't understand your footing size 3x3x4..is that inches or feet?  2x6 is a little puny for a 16' span unless you are over a 4/12 pitch.  A flatter pitch will require probably 2x8's minimum.  As far as your 28' long beam goes you are going to need an engineer to design something for that long of a span. A double 2x12 isn't going to cut it, it will  sag or collapse under its own weight.  A 28' steel beam will need to be pretty hefty for a load bearing span like that also. If you put a post in the middle of the span and cut it down to 14' spans then a double 2x12 will probably be okay.  I am not familiar with minimum roof pitches in New Jersey but it usually depends on a. the type of roofing b. the snow load.  I imagine a minimum of 2 1/2/ 12 pitch is required for the snow factor.  I believe you will need to get a building permit for this addition and will need to submit engineered drawings for it.  Contact your local building department and see what is required to attempt this project.  I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com

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QUESTION: thnx for the 2x8  recomendation
i was thinking of a like 4 or 5  2x12 glued and bolted together every foot  top and bottom.
tnx again

Answer
Hi again Jimmy, the thicker the beam doesn't necessarily make it capable of this length of span. Remember, it has to be able to hold up its own weight.  You might try contacting a truss manufacturer and see what kind of composite beams they have that are capable of making a 28' span..I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com