Polyisocyanurate Insulation Board - Installed Between Bar Joist & Roof Deck ?

[DCEngr1]

Has anyone seen rigid polyisocyanurate board installed between the top chord of a steel bar joist & the underside of roof deck? Is this done with any frequency?

 

[spats]

Never heard of it. The board goes on top of the deck. Don't you need the deck to perform as a flexible diaphragm? The deck needs to be attached to the structure, plus what braces the top chord of the joists in such a situation? It makes no sense at all to me.

 

[ztengguy]

Not a good detail at all.