Timeline - Design Evolution - Roof Cladding

Since Two Years Ago

Steel Panels

While we waffled considerably on wall cladding, roof cladding turned out to be a no-brainer.  In retrospect, it is hard to understand why there are so few steel roofs except in the southern

Asphalt shingles

states.  I am not sure how the cost stacks up against asphalt or wood shake shingles when professionally installed but, for the DIYer, a standing seam metal roof is cheaper than buying and installing his or her own shingles. We did consider "barn tin" type corrugated galvanized metal roofing that that we have admired in books and magazines but local code prohibits it. 

Cost

The cost of metal roofing fluctuates with the thickness of the metal and the way it is fastened.  Obviously, the thicker the metal, the higher the cost.  As far as fastening is concerned, there are two ways to fasten standing seam roofing -- exposed fasteners and concealed fasteners. The first utilizes hex screws with heads matching the color of the steel.  The screws have neoprene washers under the heads to seal out water. The other system typically utilizes clips that are installed first then the panels are snapped to place over them. 

Pros and Cons of Fastener Styles

(The rest of my comments are based partly on my research and partly on my having helped my step-son, Keith. install a metal roof recently.)  

The advantage of exposed

Exposed fasteners (click to enlarge)

fasteners is that the system is a third cheaper than

Concealed fasteners (click to enlarge)

systems with hidden fasteners, which is what makes the cost of metal competitive with asphalt. And they are faster and easier to install, particularly for a DIYer. 

The disadvantage of exposed fasteners is that, unless care is used in setting the hex screws so that they are not over-tighten or fail to seat fully, water will eventually follow the screws through the panels. This is one of the reasons that 30# felt is used under steel roofing.  Another disadvantage of screwed down panels is that they cannot react to the thermal expansion of the metal as it heats and cools.  This is more important as the panels get longer.

The advantage of hidden fasteners is that there are no breaks in the surface of the panels that can leak. If the panels are installed correctly, they shorten and lengthen in response to temperature changes by sliding on the clips.  The disadvantages of hidden fasteners for the DIYer is that there is a steeper learning curve and the added cost.

Slippery Slope

Installing metal roofing on a steep roof is dangerous because, unlike rough asphalt, it makes a perfect sliding board.  In my view, a DIYer might want to think twice about installing it on a steep roof.  And, if s/he does decide to do it, a safety harness is an absolute must.

Sustainability

Steel roofing is the most sustainable among roof claddings.  While it has fairly high embodied energy, it is less so than asphalt or aluminum.   It contains a high recycled content,, has a recyclable end-life and lasts longer.  It also is available in highly reflective colors which help to limit the amount of radiant heat penetrating the roof in summer. Asphalt shingles are petroleum-based, rarely have recycled content, almost always have a landfill end-life, have a shorter lifespan and lower reflectance. Shake shingles too often come from old growth trees, have a limited lifespan and end up in the landfill or, worse yet, are burned.

Our Choice

We will be using a light colored reflective steel roof.  The good-news-bad- news story is that the roof pitch is so low as to make slipping off the roof unlikely. but our budget dictates the use of exposed fasteners.

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Addendum, June, 2017
By the time I placed the order for the metal roofing, I had given up on the use of exposed fasteners due to a lower pitches to all of the roofs than originally envisioned.