Metal Roof Deflection

[Rick Burkman]

I looked at a home with a metal roof today and there were downward deflections in the roof plane. It was not a steep roof, as you can see from the photo (most metal roofs in this area are installed on a larger sloped roof), and there was an intersecting plane which can add to snow pack and ice dam formation. However, the deflections went across the entire roof plane, not just in the area of the valley. Is this the result of poor installation, previous snow load, or something that I am missing? Thanks!

[Nick Ostrowski]

How did the attic framing structure look?

[Rick Burkman]

Attic was not accessible (no interior scuttles, gable vents, or wall scuttles). The attached garage (one of the areas with metal roof deflection) trusses appeared intact and the horizontal chords and top chords were level without noticeable deflection. Roof deck was OSB with ply clips properly installed.