Expert: Bruce E. Johnson - 2/25/2011

Question
My wife and I want to close in our back porch. My question is our porch now is raised about 8' off the ground at tallest end. 6x6 are the support beams on the outside,with concrete pads.CanI used these pillar and joist to for my close room?

Answer
hi Joe, it depends more on the size and the stability of the concrete pads supporting the posts.  6x6 posts should be okay and you used the term "beams" when I think you are referring to the posts so without knowing what the beam spacing and post spacing or the size of the concrete pads it's hard to say whether or not the structure will support a roof system and walls.  If your concrete pads are 2' x 2' and at least a foot thick and reinforced with rebar and spaced no more than six feet apart with 6x6 posts supporting a minimum sized 4x6 beam then my initial response would be yes the structure should support the weight.  A local engineer could do the calculations required for a building permit if needed and sign off on the structures ability to support the additional weight.  A normal room with a normal roof can be estimated at 60 pounds a square foot so if your room is 10x10 or a hundred sq. feet you would need to be able to support 6000 pounds at the foundation.  By adding up the total square footage of your concrete pads and dividing that number into your 6000 pound overall weight it will give you a good idea as to how much each pad will be supporting.  The outside supports, however,  will be carrying the bulk of the roof load so that has to be taken into consideration also depending on how your support beams support the floor system.  At this time without more information that is about all I can say.  Please feel free to write again regarding this or other matters, sincerely Bruce E Johnson ..bejohnsonconsulting.com