Easy way to locate roof beams?
 

My 2008 brochure says they're aluminum tubing. Is there a non invasive/destructive way to locate these? Thanks

You might try borrowing someones metal detector and try that.

What Richard said.

Also, an electric cable locator system might work. One attaches a signal generator to one end of the wire which then radiates a signal which can be located by a detector. Can be found on ebay ...

... there's also the tapping-with-something-and-listening method which might work better on top.

Good luck!