The manufacturers are doing the right thing by not warrantying the Snap-Lock standing seam metal roof on low slope application such as yours (2 in 12 roof pitch). The problem with snap-lock standing seam on low sloped roofs is that if water freezes at the bottom and melts in the center of the roof, it will flood the pans between the ribs and will penetrate the roof through the locks.

There are two solutions – obvious one is of course the mechanical lock, which can go on as low an pitch as 1 in 12. The other solution is sealed snap lock, where a special course of sealant / adhesive is added inside the snap locks and seals upon contact with the lower lock. This may be an issue if the lower lock is not touching the sealant. Also very few metal roofing manufacturers provide this type of snap-lock panels. I only know of FireStone BP selling it.

You should still go for a mechanical lock instead, as double crimped locks will now let any water penetrate the roof. I would advise you however not to install exposed fasteners system on low slope roof. Though it’s commonly done, these roofs leak often and much sooner than you would expect them to.

Good Luck

Costs were determined based on material costs, and the installation difficulty and are based on my personal experience of working with this type of metal roof. I know that installation prices will vary greatly from one region to another, so I tried top average it out.

As far as longevity of the roof – they may last more than 35 years, but the exposed fasteners nailed or screwed right through the panel is the main reason that I chose that number. This is my subjective opinion, and does not reflect ONLY Decra products – the stone-coated steel roofs in general. If you want, I will remove “Decra” form the site, but this is what I think of the product. Of course there are cases of asphalt shingles roofs lasting in excess of 35 years, but also there are many cases of shingles failing in 5-10 years. Same thing with various metal roofs, and there are many factors affecting the system longevity.

Believe me – I’m not trying to take away from metal roofs in general or stone-coated steel in particular – I think metal roofs are the best for sloped roof application, but some systems are better than others. This is once again my subjective opinion based on experience of installing virtually every metal roof there is – here is my view about differen metal roofing materials: http://www.newenglandmetalroof.com/blog/metal-roofing-systems.php