Tirey & Associates, P.C.

Consulting Structural Engineers

Project: FCI/USA Roof Replacement

Location: Lincoln, New Hampshire

Completion Date: Fall, 2009


The screwed down metal roof of this 90,000 square foot, pre-engineered metal building was in poor condition, with leaks and significant ice buildup at the eave lines due to low insulation and compressed insulation at the roof purlins. The existing metal roof and insulation was completely removed, leaving only the steel purlins and moment frames. A new, structural galvanized steel deck was screwed to the purlins with rigid insulation overlaid and a TPO membrane applied on top. The use of a uniform thickness of rigid insulation yielded uniform heat loss through the insulation, thereby reducing the amount of snow melt water previously produced at the compressed batt insulation at the purlins. The use of a slippery TPO membrane promotes the slow sliding of snow, even on the 1:12 pitch roof.


This roof now experiences significantly less ice dam and icicle formations. Sliding snow cantilevers short distances beyond the eave line before breaking off and falling to the ground, in much smaller sizes than previously occurred. There is less total heat loss through the roof due to the uniform thickness of the new rigid insulation.