[Greenbuilding] roof replacement asphalt versus steel

[Bruce Donelson]

>
> steel roof
> EXPOSED FASTENERS ARE GOOD FOR A WOODSHED, NOT A HOUSE

I'd be interested in hearing the reasoning behind this statement.
I suspect that it is a prejudice that is borne out that peculiar thing we
call "taste" more than it is out of actual performance criteria.

I can point to exposed-fastener metal roofs on newish  _houses_ that have
outlasted similar-aged, asphalt-shingled roofs which one notes, have been
re-roofed two or more times in that time. (I know this because I built
some of them.)

I have seen lots of exposed fastener roofs where the fasteners wiggle out,
especially on the lower part of the roof. This is more prevalent with
lengths longer than about 20' (6 meters) because the expansion and
contraction of the metal between its coldest night and hottest day stresses
the fasteners and encourages them to back out. Often they can be replaced
with longer or thicker screws, but sometimes this process is delayed until
after the wind has picked up a sheet and "modified " it.

The concealed fastener metal roofs seem to be immune to this fastener
loosening, maybe because of the restricted space between the two metal
sheets. After I tell a customer that I would be happy to install an exposed
fastener roof for them, but that they will be responsible for tightening
down the screws, they generally see the advantages of concealed fastener
roofing. Leaks around screws that are overdriven or crooked or loosened are
not a factor with concealed fastener roof types. Less roof maintenance, less
opportunities for leaks, equal ease of recycling, and minor increase in
costs make the concealed fastener roof vastly superior to the exposed
fastener type.

I do miss being able to walk up the roof by stepping on the screw heads or
traction, though.

Bruce Donelson
A better Builder