I was up on a client’s roof in Chevy Chase the other day (this is what an architect does for relaxation) when I ran into my old nemesis – the phrase “That’s how we always do it”, and I was reminded yet again of the infinite ways that homes can be tragically damaged by ignorance – even by those who are well meaning.

Houses are complex; they are living, breathing organisms that stretch, shrink, vibrate, and sweat – just like people. But too many architects, contractors, and homeowners don’t understand the science behind houses and what keeps them healthy. All too often, they use a stock answer to solve a unique problem.

In this case, a roofer installed a new built-up roof over an existing one, not realizing that his new roof would act like shrink wrap and trap moisture beneath it. He didn’t think through the particular needs of this 1960’s contemporary, with heavy timber beams and exposed roof decking, which served as the ceiling for the house.

Humid air from inside the house was rising through the roof deck, through the old roofing via thousands of nail holes made when installing the new over-roof. Here the moisture condensed into water and seeped back through the many holes into the structure below. Gradually the water collected at the eaves, where it rotted the roof decking and the heavy timber beams.

I was looking at a total failure of a 4-year old roof as well as heavy damage to the underlying roof structure. The repair will be complex and expensive, but the real tragedy is that it was completely avoidable. When I asked one of the roofers why they installed the roof this way, he uttered the dreaded phrase “That’s how we always do it”.  But most installations of this type of roof occur over a ventilated attic – not over a cathedral ceiling of exposed timber frame – and that difference is everything.

Washington, DC and the older suburbs of Bethesda and Chevy Chase are home to an astonishing variety of house types, each with particular problems and needs. So the next time you hear “That’s how we always do it”, call an expert. It’s never that simple.