Corrugated Metal Roof Retrofit

Guest User
8/26/2004
I have an older 1.5 story home with a finished attic space. All of the rafters are 2X4 material and there is no venting system in place. It currently has composition shingles that are less than 5 years old and are failing (curling, losing little rocks) . As you can imagine, it is very hot in the summer and we have ice dam problems in the winter. I want to retrofit a metal roof over the failing shingles using purlins and corrugated galvanized steel. I can only find the 1.5 inch galvanized (mini rib) panels. I was planning on using 2x4 purlins mounted 36 inches on center. This should give me a huge amount of ventilation. Is it ok to use the smaller, mini rib for roofing applications, or should I use the larger 2.5 inch stuff? - I am using the corrugated material for ashetic and economic reasons. Thanks!
Allan Reid
Dura-Loc Roofing Systems, Inc.
8/27/2004
As you have a vaulted ceiling you need to choose a system where you strap vertically first with minimum 1" material directly over the and connected to the rafters. This will provide the vertical air flow. Then strap horizontally to receive the metal. 36" centres seems way to far and I would check with the manufacturer. I would suggest no more than 24" and better at 16". If the rafters are on 24" centres then you could use 1x4 strapping probably. Use vented closure strip at the eaves and under the ridge cap to provide the ventilation and choose a light colour. Good Luck.
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