Anatomy of a Roof

For most of us, the roof is just something that keeps the weather out of our homes. If we notice it at all, it is to consider how well it blends into the neighborhood, or possibly that a small branch has fallen on the roof and needs to be removed. In point of fact, the roof above your head is the second most expensive thing you’ll ever have to replace on your home (the whole home being the first). In short, we should all have a little more respect for that marvel of engineering that keeps the bugs, birds, bats, rain, wind, dust, hail and more out of our lives and outdoors where they belong.

Let’s take a closer look at the anatomy of a roof:

Deck: Once the rafters are up, the deck is the structural base that everything else is built on. Decks are generally made of wood or plywood.

Underlayment: The next layer is called the underlayment. It is a protective layer between the deck and your roofing material. It is generally designed to be water tight and provide a certain amount of insulation.

Roofing Material: At this point, roofs can wildly diverge from one another. For residential homes, your roofing material can be almost anything … shake, shingle, tile, metal, stone. For commercial buildings, those same materials apply, as well as additional categories like single-ply, built-up roofing, foam, modified bitumen and more.

Fasteners: Each type of roofing requires some type of fastener to attach it to the underlayment and deck … for asphalt shingles it is roofing nails, for tile, it is literally a metal fastener, for some types of roofing it is sticky tar, sticky paper or even glue that bonds the roof together.

Coating: Last but not least, these days, most roofing materials receive on final boost to make them weather resistant, a coating layer. The coating may be built into your roofing material already, or may be applied at the very end. Most of the coatings are polymers that give under impact and spring back to normal shape. Coatings can also shed heat and UV rays, thus adding extra insulation and providing a longer lifespan for your roof.

And there’s more…

So that’s it for the main layers on the roof, but there are all kinds of extras that have to get added during the process. For instance:

Flashing: Flashing is generally some type of waterproof material that is installed at the intersections of different planes of the roof (valleys, eaves, dormers, gables, hips, etc.) to reinforce those areas against the weather.

Drip Edge/Gutters: Along the outside edge of your roof, metal is installed, often along with gutters, to channel water off your roof and away from the foundation of your home.

Vents: Roofs must breathe. Intake vents are located under the eaves (and in the gables) of the roof that help draw cool, dry air into the attic and vent warm air higher up. Without this feature, attics begin to sweat (just like people). That sweat soaks into the rafters and begins to cause rot, mold and more.

Perforations: Especially here in the Southwest, with HVAC on the roofs, there are all kinds of perforations and penetrations through the roof that must be doubly protected against our fierce Monsoon weather. Then there are the vents for kitchens, bathrooms, dryers and more. In addition, we do love our sunshine here in Arizona, so lots of homes also employ skylights for extra light. These are especially vulnerable to leaks and must be carefully installed and the roofing reinforced around these areas.

Let the buyer beware…

Here’s the tricky part … improper installation of any one of these items can spell disaster for your roof and your wallet. That’s why it is so important to make sure you use professional roofers who are licensed, bonded and insured to install your roof. Check on their reputation with places like the Better Business Bureau and Angie’s List. Ask for references and call to find out if clients were satisfied with their work.