Expert: Bruce E. Johnson - 9/5/2011

Question
I purchased a home last year that has what I would describe as a somewhat unique layout.  The house is built on a traditional basement, first floor has 2 bedrooms/bath and the garage.  The second floor is a open loft style setup (tall cathedral ceilings) with dining/kitchen/living rooms open.  The master bedroom is only divided by a standard 8 ft high wall which does not reach the tall ceiling.  I would like to add a ceiling to this room to add some privacy/noise insulation as well as some additional living space on top.  The actual room is 14' x 14' with two walls being outside walls and the other two walls being the 8ft high walls.  I am a mechanical engineer (automotive) and have done a number of house renovations but I am not sure how to tackle this ceiling project to make sure it is properly done.  My current plan would be to add a beam across the center of the room then run joists off of that connecting into the existing walls.  Is there a rule of thumb for this type of project or would I need to consult some type of engineering company to provide some specs?  If that is the case how would I go about finding someone to do such a small job?  Hiring a general contractor is an option but so far I have not found any in this area that I trust beyond my own capabilities for a project like this.  
thanks

Answer
Hi James, this isn't too big of a deal for an average home handy man.  As far as spans go, 14' can be spanned with a 2x12 joist without a center beam or you can use a 4x12 center beam and hang 2x8 joists for the 7' resulting span.  You might want to make sure your 8' walls have decent bearing, sitting on something other than floor sheathing, otherwise the added weight of the new floor system may cause the existing floor to sag.  You will also be increasing the load on your existing floor joists so hopefully you have a good floor system as well.  Truss manufacturers handle laminated beams and I-joists which may come in handy if you have height restrictions that preclude you using 12" deep material.  Truss plants also have engineering tools to help determine the maximum or minimum size material needed.  Sincerely bruce johnson