I'm moving my shed from the city to my piece of property in the country. I've got some metal roofing laying around but have never used this type of roofing material before. I'm thinking of using it instead of the shingles that were on there in the first place. Btw, the slope on this shed roof is about 2 in 12, if that really matters.
Pitch matters.
Some roofing materials will not be approved by the manufacturer for low pitches. In other words they will not warranty the roof if applied to too low a pitch. It may leak. Check with the manufacturer of the metal you have to see what they recommend. The Fabral I have used calls for a minimum pitch of 2.5 / 12 for example.
You can seal the overlap on ribbed metal roofing material by using butyl rubber tape in the lap joint.
2/12 is at the very limit even for asphalt shingles, and often they will recommend alternate installation techniques (http://"http://www.casma.ca/installation-of-asphalt-shingles-on-low-sloped-roofs#.VfQgc41RHIU") when under 4/12 pitch, just to help resist against water penetration and ice damming if in a colder climate.
The only easy option I know of for a 2/12 roof is rolled roofing, unless you want to get into hot mop and rock. You might be able to put your metal over something like that but it might not last very long
Some metal roofing that is used on metal framed buildings can go as low as 3/4-12 pitch. it has a very high ridge and span up to 8' between purloins depending on your snow load.
Well, I installed metal roofing the other day and am sold on it. It was easy and fast. I would say about half the time of what it would take to install asphalt shingles. We had a down pour today and it was bone dry in the shed. But I made a wide ridge cap to overhang on both sides of the peak to ensure that rain isn't driven up and under.
Pics please... in our minds it never happened if we don't see the proof. ;)
We installed metal roofing on our porch in June of 2012. It has about a 2/12 pitch in Northern Arizona. We don't get a lot of rain, but when we do, it comes down hard and fast in most cases. Never a leak. These are the metal panels that overlap and snap together, with the screws being completely covered by the metal. So there are no perferations to the top side.
(http://www.arizonaranch.org/root/arizonaranch.org/wp-content/uploads/2012/06/DSCN0327.jpg)
We used the same metal roofing on our main roof in August of 2007, and never a leak there, either. The install was so easy, I swore I would never use asphalt shingles again...
(http://www.arizonaranch.org/root/arizonaranch.org/wp-content/uploads/2012/07/DSCN0409.jpg)
(http://www.arizonaranch.org/root/arizonaranch.org/wp-content/uploads/2013/03/DSCN0687.jpg)