Every house should have roof overhangs, except when they shouldn't or can't
In his column titled Musings of an energy nerd, Martin Holladay claims that every house needs roof overhangs. Now I happen to be a big fan of Martin's writing, and completely agree that we have much to learn from the traditional ways of building; there are reasons people built this way. I have sometimes taken such extreme traditional positions that Martin actually called called me a Luddite.
But when it came to the renovation of my own home, I reverted to type; I am at heart a modernist. I was also not a very good architect during my short career, and learned early to hire the best. There are enough lousy buildings by lousy architects. So I hired David Colussi of Workshop Architecture, winner of the Top Emerging Practice award for 2013 from the Ontario Association of Architects, where I am a past Vice President, so I trust their judgement.
Martin is right; good overhangs are absolutely the right thing to do. If you don't have a parapet and a roof deck above for the upstairs apartment. If you don't have ridiculous building regulations demanding noncombustible construction on the sides. If you don't have setback regulations limiting overhangs to uselessly small dimensions. If you don't mind cantilevered joists breaking your thermal envelope and causing discontinuities in your cladding. If you are facing south where the shading effect might make a difference.
© Workshop Architecture/ Rear elevation
There is, in fact, a lot of modern technology that works rather well at keeping water off my house; there is a pressure equalizing rain screen wall made of Geoboard, (coming next week) a cement and fiber mixture that is waterproof and is the first line of resistance. Then there are my sticky orange frogs, the membrane that keep the water out. Cascadia clips that hold up the siding without acting as thermal bridges. Flashing on top of flashing on top of flashing. Aluminum clad windows that won't rot in the rain.
If you do design it carefully, use high quality materials and build it properly, you don't have to be doctrinaire and say "every house should have roof overhangs." I was convinced that this design will stand the test of time.
Lloyd Alter/CC BY 2.0
Then we had our first downpour since the windows were installed and my open casement was getting soaked inside and out, and I was getting wet sitting right next to it. And I thought, a roof overhang would be really nice right now.
Perhaps Martin is right, houses should have roof overhangs. But there are a lot of reasons that go beyond aesthetics why one might not. My wife said, "suck it up and close the window", which I did, and opened up some of the others that were awnings. We will report back in 20 years.
Lloyd Alter/CC BY 2.0
Martin is also correct when he says that you can do roof overhangs in modern design; Frank Lloyd Wright did it all the time. A great example is the Darwin Martin House in Buffalo. But it helps to have more than a 30' tight urban lot.