Expert: Bruce E. Johnson - 9/12/2008

Question
live in Jacksonville, Florida and am considering building an outdoor porch on an existing concrete slab that is 35 ft long along house that extends out 10 ft.  The house is concrete block w/built-up flat tar roof; concrete slab is 30 inches or so below the first floor elevation of the house; so porch roof supports would be about 12 feet high; how would I attach a simple sloped roof using the colored
aluminum panels popular in some south Fl home building?  Where could I access some simple designs?  Thank you for help.


Answer
Hi martin, not sure where you can access designs related to your project, try this link (http://www.coolhouseplans.com/links.html?searchCategory=Porches) however it is a simple process to build a roof structure like this.  Plus you might need a building permit so you may have to have an engineer design and seal a set a drawings for the building department.  Simply put, you attach some 4x4 posts to the concrete using post base anchors.  The posts hold up beams.  Your beams should be sized according to span.  Normally one foot of span for one inch in depth.  In other words for 8 feet of span you would use a 4x8 beam, 10 feet, a 4x10, etc.  So your post spacing will determine your beam size. The posts are connected to the beams with appropriate Simpson post and beam connectors.  The roof structure will consist of probably 2x8 joists at two feet on center the joists are connected to the house via a ledger made of the same material bolted to the studs and the joists in hangers on the ledger.  The joists then sit on the outside beam and are connected through Simpson h-clips. Then you need to cross those joists with purlins, 2x4's laid flat across the joists at 12" on center.  These purlins are what you attach your roof panels to. I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com