Expert: Dan Griffin - 9/30/2009

Question

    The second story of a home I am buying in California has a beautiful view of a small orchard through 2 large wide windows in a wide dormer in a gambrel roof.  I would like to remove the window, put in French doors and a small cantilevered balcony.  The existing floor joists are 2 X 10, 16" OC.  I would like to tie in to these to cantilever the balcony. Putting in french doors in the dormer means the threshold of the door would be 18 inches from the edge of the exterior wall which supports the second floor.  What I would like to do is run the sister joists out 3 feet beyond the exterior wall to give a balcony that would be 4-1/2 feet by 8 feet wide.  I guess I need to see if the California code will allow this, but I'm also wondering how much weight such a cantilevered balcony would hold.  I suppose I could also put some corbels underneath the balcony for support.  I could even run support beams from the edge of the balcony all the way to the ground, but I am trying to avoid this if at all possible.  Anyway, just wondering if you have done anything like this and what is a safe way to approach this.  Bob

Answer
Bob, I would discourage using cantilever.  YOu are very limited on cantilever distance in structural settings and the flashing and waterproofing are quite problematic.  Even the corbels will require some major wall stiffening.  I think your best approach would be work with a structural engineer to consider this one.