Rain or Shine: How Roofs Withstand the Test of Time – Part II: Roof Design and Weather Resistance

When it comes to longevity and resisting the elements, no two roofs are exactly the same. The fact that different roofing materials have different expected lifetimes serves to stress this. But while it can be argued that balancing cost, durability, and service life is a matter of trading off different factors to find a solution that will meet your needs the most, it is a fact that certain combinations of materials and engineering make for roofs better able to resist weather damage.

Roof Design

Wind primarily affects roofs in the form of uplift. The more sloping surfaces a roof has, the more resistance it has to wind and uplift forces. This means that a hip roof, with four sloping sides, will be able to resists strong winds better than the more common gable roof, which only has two slopes.

The Danger of Overhanging Areas

Projecting surfaces and large overhangs not only provide areas for the wind to latch onto and tear at your roof, but also makes the overhangs inherently weaker at resisting the effects of the wind. If you’re getting an entirely new roof, keep in mind that gable ends should be avoided and whatever overhang your roof might have should not extend beyond 20 inches from exterior wall edges.

Roof Pitch

A roof’s slope also plays a part in resisting hurricane-force winds. To maximize resistance to uplift, you want a roof with a 3.6/12 slope, meaning it rises 3.6 inches for every 12 inches that it extends. Generally though, roofs with pitches ranging from 4/12 to 6/12 will also do well in offering wind-resistance. Aside from resistance to wind, a roof’s pitch also helps determine how well it will shed water. Typically though, the steeper the roof, the faster it sheds, minimizing water damage.

Paying particular attention to roof design can help you fashion a roof with optimum weather-resistance. In Part III, you’ll be learning about the other things you can do to keep your roof in shape no matter what the elements may bring.