[Greenbuilding] roof replacement asphalt versus steel

[Chris Boyd]

Re: [Greenbuilding] roof replacement asphalt versus steel

In my experience in the commercial and industrial building world, the
main problem with exposed fastener roof systems had nothing to do with
the panels themselves.
The problems were with the fasteners.
Each fastener (hundreds or thousands on a typical roof) is a penetration
of the roofing material that is exposed to the elements.
The rubber washers under the fasteners are meant to seal that
penetration and protect the integrity of the weather barrier.
Unfortunately the washers are directly exposed to horrific conditions
for a flexible rubber material: heat and cold extremes, wet and dry
cycles, UV light, etc.
It is commonly the fasteners (or the washers under them) that fail, not
the metal roof panels.
One exposed fastener roofing company recommends that the washers be
replaced every 15 to 20 years.  (I have never heard of this being done.)

The alternative could be to install the exposed fastener roof over a
rain screen and strapping much as we would install siding.
That way any minor leaks in the roofing itself are still kept out of the
roof structure by the drainage plane.

Chris Boyd
Project Planner & Estimator
 
Taggart Construction, Inc.
BUILDING GREEN SINCE 1994
 
cboyd at tagcon.com
207/ 865-2281 x2
 
www.tagcon.com