Anatomy of a Roof

Roofing 101

Ventilation is an integral part of making a roof last, and occurs naturally when vents are placed at the base of the roof (at the eaves or in the soffits) and near the top of the roof (the ridge) so that warm air can leave through the top, and cool air can be drawn through the bottom. This process does not need electrical or mechanical fans in most cases, as nature will do the work on its own.

When vents are placed you should be aware of the following guidelines:

1. Vents should not be inserted into the middle sections of the roof, since this will often interrupt the natural circulation of the air. Instead, evenly distribute vents along the roof, to ensure even airflow to all portions of the roof.
2. Approximately half of the vents should be placed near the ridge and the other half near the eaves or soffits, to encourage maximum airflow.
3. Approximately 1 square foot of ventilation per 300 square feet of attic floor space should be included in the plans for your new roof (this is an approximate and depends on climate, roof pitch, orientation and available attic vent space).

Types of Attic Vents

1. Soffit Vents - Able to be used as either inlet or outlet of air they are best combined with a ridge or roof vent.
2. Gable End Vents - Vent placed at the top of the gable area on both ends of the house.
3. Ridge Vents - Vent placed along the entire ridge of the roof to allow hot air to escape as it rises to the top of the attic space.
4. Roof Vents - Available in a standard or powered version this vent is best installed toward the top of the roof.

If adequate ventilation is not installed, serious problems such as attic condensation, wood rot, mold, mildew and rusting metal will occur. These problems can affect the integrity of the roof as well as the integrity of the house, and can even cause health problems for family members in the home. One of the biggest roof problems associated with improper attic ventilation is an "ice dam".

Starter Strip - Asphalt roofing applied at the eaves that provides protection by filling in the spaces under the cutouts and joints of the first course of shingles.

Drip Edge - Edging that is placed at the end of the roof (end of the eaves) used to allow water to run-off and drip clear of underlying construction.

Facia - Trim used to cover the rafter end of the eaves. Often where gutters are attached to the house.

Soffit - A finished underside of the eaves. Covers the area between the end of the eaves and the house.

Underlayment - Often called tar paper this heavy felt paper (synthetic materials are available as well) is placed on top of the decking before the roofing material is installed to offer an additional layer of protection from moisture.