Expert: Stephen Major (Owner--Major Design Group) - 7/14/2007

Question
I live in hot S. Florida and I have an attached garage which was converted into a livingroom.  Problem is, the room is lower than the rest of the house, and is also sloped--8" lower at one end and 10.5" at the other.  The entire structure is CBS.  I want to build a wood frame out of 2x6's to bring the room up to meet the rest of the house.  Can I use joist hangers to butt the joists to the frame?  Joists will be 16" apart at dead center?  Do I need to insulate the floor?  I'm not sure how to do the sleepers or supports or how far to space them, either, what with the slope and all. The sunken "room" is moisture free, so I'm not at all worried about mold.

Answer
Tony,

Joist hangers are OK in this application.  I recommend that all framing be of pressure-treated lumber.  Moisture can accumulate in a space like this and could lead to mold, regardless of the current moisture conditions.  

Joists should be 16" o.c.  Don't allow a 2x6 to span more than 7 feet unsupported.  You will need to build up flat 2x4s or 2x6s to make support "beams".  Fasten everything together well or you will have squeaks.

Insulation is not necessary, but in any event you should lay down a 6-mil poly vapor barrier prior to constructing the floor.  

If I was doing this I would pour concrete.  It's less work and more reliable, especially in your region.

Best of luck, and let me know if you have additional questions.  

--Steve Major