|This is one of those try it and see applications. Due to the mass of the walls, probably your best bet would be to try and capture the structural beams under transient temperature conditions.
Set up a camera and record an image every 15 to 30 minutes for a 24 hour period for which you have clear skys (night and day) and low wind. Ideally you want sunshine to heat the walls during the daytime.
Then review the images to see if anything pops up for structural details.