8" joists, 15' span

[Katharine Chartrand]

I am putting an addition on an old house that has 8" floor joists. For various reasons, it's very problematic to change the ceiling height between the original house and the addition. However, the smallest engineered floor joist I can find is 9 1/2". 

Code allows me to span 15'7" with 2x8" on 12" center. That's currently the only option I have, however, I've been told my floor will be bouncy.'' Is there anything else I should be considering?

[Jon Holdman]

I would recommend, and have, hiring a structural engineer for situations like these.  It should only be a few hundred dollars.  In my case he was able to give me much simpler solutions than I was expecting to have to install.  An engineer stamp may be needed on your plans in any case, when you go to get permits.

You might be able to doubled up 2x8s.  That gets you from 2x8 joists to 4x8 joists.  Or perhaps add a beam below the new joists.