[Greenbuilding] roof material for rain harvesting

[RT]

>> On Thu, 15 Aug 2013 22:15:51 -0400, candtcampbell at juno.com  
>> <candtcampbell at juno.com> wrote:

>>> I've read that the best roof for rain harvesting is simply unpainted  
>>> galvanized steel (not galvalume).

> On Thu, Aug 15, 2013 at 7:43 PM, Topher <topher at greenfret.com> wrote:
>> If it is, available in rolls (which seems to be the case), you should be
>> able to do a standard standing seam roof, that way.

On Fri, 16 Aug 2013 00:24:03 -0400, Reuben Deumling <9watts at gmail.com>
wrote:

> can you explain the rolls bit? My impression of standing seam roofs is  
> that  they come in panels.


I'd venture that the "best" roof for rainwater harvesting would be  
tempered glass ...and if the glass is from diverted-from-the-wastestream  
patio door insulating glass units whose edge seals have failed (IGUs then  
separated to yield two panels) one would be hard pressed to find a more  
Green roof material (chemically inert, indestructible, never needs  
replacement).

But on the subject of standing seam metal roofing:

Sheet metal flat stock is typically 36 inches wide but 48" wide stock is  
available from Murrican mills.

Any company that fabricates pre-formed sheet metal roofing buys the sheet  
stock in big coils that are at least 4 ft (or more ? ... it's been awhile  
since I've been in a fabrication plant) in diameter requiring a fork lift  
to move. At the retail level, utility coils of 50 and 100ft lengths which  
are manageable by hand, are typically available. The local building supply  
is likely to keep 36x96 or 36x120 inch flat sheets on hand.

The old rule of thumb (from the days when pans were formed by hand on  
site) is that standing seam pans should not exceed 18 inches in width.

I've made standing seam pans on-site in the past using 28 and 26 gauge  
Galvalume stock, working alone -- a walk in the park.

It's simply a matter of making two (or three, depending upon seam lock  
detail) bends along each longitudinal edge of the pan stock. A couple of  
10ft-plus lengths of steel angle (3"x 3" x 3/16" is a nice manageable  
size) with a few F-clamps and/or C-clamps makes a very serviceable brake  
press.

This setup enables one to fabricate custom-shaped panels, useful for  
non-rectilinear roofs (like say for that ziggurat design that looked so  
nifty on paper ... or that reciprocal roof that was so awesome-looking at  
the framing stage  ... but became a nightmare to put a roof on. )

-- 
=== * ===
Rob Tom					AOD257
Kanata, Ontario, Canada

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