Expert: Bruce E. Johnson - 3/23/2010

Question
QUESTION: Building a 24x26 garage w/ two 9ft doors along the 26ft length ceiling height 11ft. At the 12ft mark and down the 26ft length was wanting to start a second floor system for an enclosed loft about 7ft tall for storage. Along the back load bearing side, will be ok down to the foundation but the load bearing side on the other end and down the 12ft line the second floor wall system will have to set the entire 26ft length on a girder spanning at least 13ft Was hoping to put only one support post in the garage floor if possible Would this be feasible to do and if so what size girder would be sufficient to carry this load. Would use 2x 10 floor joists and 2x 4 studs to match up to the back of the building now in place that i am butting this addition up to. This second floor will only finish up about 12ft x26ft with 4/12 pitch roof. Your question may be why doing this? The existing building has an open shed roof on it and I wanted to continue the roof line of the shed roof to the new part becoming half of the roof for the new garage addition Also the existing building is a barn style two story as this may be helpful to understand what i am wanting to do   Thanks very much

ANSWER: Hi jeremy, to carry a 12' span of floor load I would say a double 2x12 or 4x12 beam of conventional lumber or a double 1 3/4" x 12" LVL laminated beam.  Would suffice.  Check out this span calculator.  www.cwc.ca/Resources/E-Tools/SpanCalc.

It is a handy tool for working out spans etc for the application involved.  I hope this information helps. Please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com

---------- FOLLOW-UP ----------

QUESTION: Would using laminated floor joist sixteen inches on center eliminate the need for a support beam and a support pole in the garage area???? They would have to span the full twenty four feet. Only twelve feet by twenty six feet would become floor space for second floor and the remaining would become attic space so the other half of the joist in essence would become ceiling joist . It would be nice not to have a support pole in center of the garage floor.If so,what size  laminated floor joist do you think would be needed to accomplish this???????

Answer
Hi again Jeremy, a 16" deep wood I-joist or 16" deep LVL laminated joists set at 16" on center should span the 24' you require.  This system will also require bridging, either metal x bracing or solid blocking every 8' in continuous rows between the joists. I hope this information helps. Please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com