The mountain – valley juxtaposition as a metaphor is, well, as old as the hills. It’s very accessible and can be readily experienced, and it exploits a meaningful ambivalence. As Winston Churchill put it, “Mountaintops inspire leaders but valleys mature them”. In other words, a different challenge and reward can be found in each. Valleys are fertile and rich, growing food and sustaining life, but they can also be isolated, inferior strategically, and prone to flooding. “Yea, though I walk through the valley of the shadow of death…” Mountain tops are an accomplishment to achieve but can be precarious and barren. An optimist sees opportunity in both; the pessimist sees peril in both. It is all there: the good and the bad, the positive and the negative, all neatly presented in the opposition.
Driving around the beauteous Shenandoah Valley, I get to experience this dynamic pairing quite often. But whether I’m in the Valley or further east, ridges and valleys are part of more home inspections than you might think. How you ask? Easy. Roofs are nothing more than ridges and valleys. Even straightforward roofs with just two faces are a mountain with two small rives (gutters) on either side. Like geographic mountains, roofs vary quite a bit in their complexity and composition, and the arrangement of a given roof has a direct bearing on its effectiveness when it comes to channeling the water around it.
Building science guru, Joe Lstiburek, of the Building Science Corporation, has a humorous visual analogy to illustrate the difference in how the thinking of builders and engineers differs from that of architects when it comes to roofs. He takes a piece of paper and folds it in half, creating a simple two sided roof as a representation of how builders and engineers conceive of and think about roofs. Then he crumples up the bifolded paper into chaotic mess to show how architects think of roofs. Humor and hyperbole aside, the point is that the more complicated the roof lines are, the greater the potential for problems.
Now, roof valleys as a whole are not problematic. If well-engineered and well-installed, they can be an effective means of controlling water. However, when valleys are terminated against vertical walls, they can become vulnerable areas where rain, snow, and leaf debris can get trapped, holding moisture against the roof and walls.
From the 1950s through the 1980s rooflines were, for the most part, fairly straight forward. This was the preferred style. Think of the venerable brick ranchers that can be found around every turn in the greater Winchester area. Sure, homeowners added rooms, porches, and even whole wings, but it’s rare to see dramatic peaks and valleys atop these houses. Beginning in the late 80s, the preference for more dynamic rooflines began to increase. Roofs got steeper, more perpendicular orientations appeared, and the height of roof sections began to vary quite a bit.
A byproduct of these changes is that lower roofs are sometimes terminated against sidewalls. The classic example is the garage roof that runs into the sidewall of a two story foyer. Here, all elements of the mountain-valley dynamic are in play. To create a dramatic, stark roofline, narrow valleys have to channel gallons of gushing water. Now, we all learned in elementary school that the churning of the Colorado River created the Grand Canyon across the millennia. Coincidentally, it takes water a much shorter time to work through tar paper, felt, and wood. Roofs that abut sidewalls are problematic. Historically, it turns out, we’ve done a poor job of trying to out-engineer Mother Nature. Still, we try with narrow roof valleys.
Oh – we also routinely make an already vulnerable area much more so. In houses from the early 1990s onward, I routinely see downspouts that discharge into these narrow roof-to-sidewall valleys. Adding more water to an already problematic passage is, go figure, not a good idea. Even if the valley flashing – the water-tight covering under the shingles – is perfect, this is still a less-than-ideal arrangement. You may have noticed that water flow and volume are rarely consistent, rain shower to rain shower. Think about it this way. What is smarter? Standing by a river in waders during a rain storm or moving to higher ground? Right. Avoid the bad idea altogether.
If, perhaps, you have a home with a vulnerable valley, make sure that it stays clear of leaf and snow debris. I once meet a seller who claimed to blow leaves off the roof from the master bedroom with a gas powered leaf-blower. This would work, but you might want to run that by your significant other first. Battery powered leaf-blowers have become surprisingly effective. Also, if some recalcitrant roofer dropped a downspout in a narrow valley at your house, have a qualified roofer or landscaper add and extension to that downspout that directs it an adjacent gutter or down to grade.
If you are showing or looking at houses, look for narrow, vulnerable roof valleys and then study the interior walls beneath like they’re a Picasso. Any discoloration or staining could be sign of water damage behind the wall. Even as a home inspector who angles through attics, assessing the full extent of hydro-harm can be difficult. It often takes invasive investigation by a carpenter to completely uncover the conditions caused by a roof leak. Given that they are cheap, investing in a handheld moisture meter isn’t a bad idea either.
Simple roofs are boring but effective. Complicated rooflines evoke glorious grandeur, but they can be a bear to install, maintain, and repair. It’s all there: the mountain and the valley.
 The western chalet style houses that can be found a higher elevations are an obvious exception.
 I mean simple in terms of roof faces, not pitch. Steeper pitched roofs are universally more effective when it comes to shedding water and have a greater longevity.