Installing a metal roof

Asphalt shingles are so passe. They use carbon resources. They seldom last as long as advertised. They are a pain to rip off and dispose of. The roof sheds them as the base felt paper disintegrates over time.

And for centretown type houses, often three stories tall, and on narrow lots, the labour cost of replacing them far exceeds the cost of the shingles themselves.

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above: a bit of shingle roof as seen looking down from my third floor windows. The eave of the roof has eavestrough.Below are more pictures from the same position as the new steel roof is installed.

Chasing down alternatives was not easy. I was horrified by some of the recommendations of roofers. Many offered to screw metal sheets directly to the existing shingles, with no ventilation space under the metal (moisture condenses on the bottom of the metal sheets, and needs to dry; and we don’t want thermal expansion and contraction to grate the (hopefully galvanized) bottom of the metal panels against the abrasive grit on the old shingles. The ventillation gap should also reduce summer heat gain. And don’t get me started on the weird combination of shingle grit applied to the top of metal shingles.

I checked out metal shingles, ie small metal sheets, sometimes of aluminum, sometimes steel. They look a lot like traditional shingles but are full of joints. One benefit, in my mind, of large sheets is that there is no joint from the peak of the roof to the eaves. Fewer joints, fewer leaks; and fewer spots for the wind to grab onto.

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above: shingle-like metal roof spotted elsewhere on the west side. There doesn’t appear to be ventilation directly beneath the metal. The fins are snow guards to break up falling ice.

Eventually settling on heavy gauge steel roofing, the contractor first wrapped the roof with a breathable waterproof membrane, more like a heavy duty canvas than plastic house wrap. They then put battens above each roof joist. And ran cross pieces, to give a 2″ air circulation gap, that vents from the bug-screened eaves up to the vented roof peak.

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above: view from the third floor window with membrane and battens installed.

The type of roof I chose has a European profile. It won’t be mistaken for asphalt shingles. Many metal roofs in Ottawa use long vertical patterns, sort of like barn roofs and commercial corrugated siding:

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above: houses on Bronson with traditional-style “farm house” metal roofs

The Euro profile looks a bit odd in Ottawa today; but where these roofs have been making huge inroads into the SW Ontario market (London, Stratford, Niagara) they can now be seen on pretty much every block and by dint of repetition the Euro profile becomes normal.

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above: same third floor view, with new metal roof. There are not horizontal seams, the fold is part of the pattern stamped in large sheets.

Colour guarantee: 50+ years. Roof life expectancy: 100+ years. Cost: about twice that of shingles, so the payback period is less than 20 years, ie when you don’t have to reshingle. And if I am around in 2150 I can sell the metal to be recycled.

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above: snow and ice can “let go” and slide off the roof. Snow guards break up the mass of snow. 

And no, the metal roof does not give a “rain on a tin roof sound”. That’s a product of Hollywood movies, or southern locales where tin roofs have nothing beneath them. The plywood and insulation of the roof mask all sound. On the asphalt roof I used to hear squirrels running across, usually at 5am. Squirrels don’t seem to find the same traction on metal as I never see them there.

Of  course, maintaining a 110+ year old home is never done. Next, the flat roofs out back, then the kitchen counter, then …

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above: roof of the front porch dormer prepared for the roofing material.

One thought on “Installing a metal roof

  1. I’m nitpicking, but that’s Beech St not Bronson. 🙂

    We used a metal roof at our cottage and love it. I see more and more of them around the city, and I think they look great.

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