A ridge cap is a building material that is installed along the ridge line of a sloped roof. A traditional gabled roof on a home is made up of two sloped sides that meet in the middle. The point where these two sides meet forms the apex of the roof, and is known as the ridge or ridge line. A ridge cap fits over the joint between these two edges to keep rain and snow out of the home. It also helps to finish off the look of the roof by creating a tightly sealed joint along the two sides.
Some form of ridge cap is used on almost every kind of sloped roof. The most basic type of unit consists of asphalt shingles, which are cut to fit over the ridge. The shingles are installed in overlapping rows until they reach the ridge, then wrapped over to meet the other side of the roof. A second set of shingles is cut to fit over the top and to provide a cohesive finish to the roof.
Some builders may use pre-fabricated roof caps when installing roofing systems. These units can be made from asphalt shingles, aluminum, copper, or even plastic. They are generally chosen to match the rest of the roof surface, though some may simply be covered by additional roofing material. Many uncovered ridge caps are painted, or they may be pre-finished at the factory in a variety of colors and designs to match popular roofing materials.
A ridge cap vent is often used to help ventilate the home, which can lead to improved energy efficiency and greater levels of comfort for occupants.To add a ridge cap vent, a hole must be cut along the entire length of the ridge to create air flow. A plastic or metal vent is nailed over the ridge to cover this hole, and is then covered with shingles or a separate ridge gap to create the desired appearance.
Most ridge cap vents are baffled to allow hot air to escape without letting water enter the home. They feature an inverted "V" shape that fits over the ridge while sitting slightly above the surface of the roof. Because water can't travel uphill, moisture is not able to penetrate the home through these vents. This baffled structure also helps to keep out dirt and leaves, and minimizes the impact of wind gusts. Some ridge cap vents may use a mesh screen to keep bugs and other pests from entering the home.