Expert: Dan Griffin - 3/24/2009

Question
Dan, I need to build an office in my small warehouse. the dimensions of the entire warehouse are 20'x50' and i'm wanting to build an office 20'x20' in the rear. I need the roof/ceiling of the office to be able to carry a load so i can store supplies and furniture in that space. any recommendations on the minimum spacing for the beams and thinkness? the other question I had was regarding the supprt of the roof/ceiling...considering the 3 walls i'm working with are mearly fire rated dry wall i figure i'd have to support the roof/ceiling using 2x4s do you thinks that suitable. I Look forward to your response. any help would be greatly appricated.

Answer
Roger, this can be a fairly straight forward project.  The scary thing is for either of us to know what kind of weight you are going to put up there.  Right now you say just a few things, but sooner or later it becomes a junk haven "oh, stick it up there" takes over.

YOu can use normal dimension lumber #2 yellow pine 2x12's on 12" ceneters to clear span the 20' dimension.  This will allow 50#/SF live load.  Paper or book storage can get to 100 #/SF.  I imagine this work will need to be inspected, contact your code authority for a claification on material and load requirements.  Be very careful using the word storage, call it additional work space or something else.  YOu should look at some alternate materials like LVL Trussjoists or othr manmade lumber - ask for sizing and costs at your local lumber yard.  This might also be an excellent candidate for metal studs work.  Contact a local commercial drywall supplier (not a lumber yard or box store) to double check my numbers using Deitrich or similar metal stud materials.  I think you can make the span with a smaller dimension.  I also know you will need a substantial safety rail on your deck.

YOu will need to verify what your present stud situation is and how you might attach a ledger board.  It is possible that you may not need to supply an additional stud wall on the back wall.  If you were going to need to install electric or plumbing anyway, it might be easiest to just crate a new stud wall, though I would use metal to furr out.