[permaculture] Roofing materials and water collection

Lawrence F. London, Jr. venaurafarm at bellsouth.net
Fri May 13 21:23:07 EDT 2011

On 5/13/2011 7:49 PM, Stephen Sherman wrote:
> We have a small building which is going to be roofed, and I am in the
> middle of choosing a roofing material. I would like to keep the option
> of collecting roof runoff open, and keep the roof as fireproof as
> possible. Those are the primary concerns for this choice of roof.
> I have heard/read the negatives about using water which came off asphalt
> shingle roofs, so those are probably not an option. That would seem to
> leave only a few choices:
> Ceramic tile roofs are out, due to their weight and structural concerns.
> Galvanized metal roofing seems like the best choice perhaps, for easy of
> use, fireproof-ness, and runoff quality (as far as I have heard).
4) The Best Choice
> Another potential option is painted metal roofing (usually available in
> wider sheets than the plain galvanized, and longer lasting. Only problem
> is no manufacture seems to have any data about runoff water quality from
> their painted roof materials.

I would avoid asphalt/fiberglass etc.; ceramic is not really an option, 
plain 5V (24") galvanized will rust and require maintenance

Painted, galvanized (I assume it is galvanized under the paint layer) 
metal roofing comes in any length and in  38" width with 5 separate, 
evenly spaced gullets (rounded ridges) affording many overlap options to 
accomodate roof framing specs without cutting the roofing panels 
lengthwise which would bugger up the edge and break the paint coat. This 
is maintenance free and will last a lifetime. It may be heavier gauge 
than 5V and for sure you can get the industrial grade of this type of 
roofing that is very heavy gauge and with deep square overlapping 
gullets; this last option will last hundreds of years. I have used both 
5V and painted but will only used the prepainted for any new work or 
maintenance. If you have to cut any to fit framing then use a simple 
curcular saw with a sheet metal cutting blade. Works fine. It is a flat 
smooth/square edged disk with many short slots cut around the edge 
radially toward the center. It cuts by tearing or ripping and not by 
abrasion. You can use this blade to cut panels lengthwise and across.
The fastener system ussed to attach the painted metal panels is superior 
to that available for the 5V, partly because of the limitations
imposed by the V's, only leadhead, acorn or neoprene washer nails are 
available though now there may be neoprene washer galvanized screws to 
use. This latter fastener, though heavier gauge than used for 5V, is 
what is used on the 38" painted metal panels. They say you can screw 
them through the flats but I would never do that, only through the 
overlapped V gullets (they are more like U gullets).
I can take photos of both metal systems if you want to see what they 
look like installed and which has rust and which doesn't.

> I was wondering what people thought about these options; If there are
> any others which I've missed;  and if anyone had any hard data on
> painted metal roofing leaching whatever into the water runoff.

 From my experience and knowledge 5 U galvanized/painted 38" metal 
roofing is the very best option, nothing else can come near for ease of 
installation and durability as well as giving the owner-builder more and 
better design options.

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