[Greenbuilding] metal roof question

RT ArchiLogic at yahoo.ca
Tue Aug 26 19:30:03 MDT 2014

On Tue, 26 Aug 2014 20:03:09 -0400, Reuben Deumling <9watts at gmail.com>  

> wondering whether for a 20" roof (housewall to soffit)use a single strip  
> of metal running horizontally, with a 3/4" lip at the top to slip under  
> the course of wood siding,and a ~2" lip at the bottom, like that soffit  
> metal has?

I'd say that the above would be the logical approach so long as the  
horizontal length of the roof isn't too great but even if it is, it  
wouldn't be difficult to resolve.

Much of it could be resolved by increasing the height of the upstand at  
the top edge  from the proposed 3/4" which is too short to begin with IMO.

Increasing the height to say 6 inches would help to make the panel more  
rigid and less likely to buckle during the process of getting it from the  
ground up to the roof.
One could of course, simply clamp the panel to some sticks of wood to  
prevent buckling but I'd venture that the upstand should be at least 4 to  
6 inches to provide protection against leaks (ie wind-driven rain).

I'm not sure what the "2 inch lip at the bottom means but if I were  
detailing the bottom edge, I'd provide at least a one inch overhang at the  
fascia and incorporate a drip edge.  I'd design it so that a drip-edge  
flashing is installed first and then have the bottom edge of the roof  
panel fold-lock over the drip-edge flashing using it like a cleat to  
anchor the roof panel without the need for exposed fasteners.

And if the auxiliary roof is designed as a hip roof, I'd also incorporate  
fold-lock seams where the panels meet at the hips (with hold-down cleats  
installed on the first panel) eliminating the need for a separate ridge  

All of the above can be formed into the panels on site using no much more  
than a couple pairs of duck-billed locking pliers and some appropriate  
lengths of steel bar to use as straight edges to form the bends.

=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at  Y a h o o  dot  CA >
(manually winnow the chaff from my edress if you hit REPLY)

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