Understanding Roof Slope and Pitch

Any time you are discussing a roof with a Portland roofing contractor; the roof span length, run of the roof, rise, pitch, and slope will be factored in building, repairing, or replacing a roof system. Here are some basic terms and explanations used when building a Portland roof.

Roof Span is the length of the roof, which includes both angled sides from the peak to the bottom edge.

Rise is the amount of distance from the peak of the roof to the low end of the roof. This is measured is determining the pitch or slope angle.

Run is the measurement to determine the vertical rise of a roof’s slope. For every 12” there will be some vertical rise, that 12” distance across is the run.

Roof Pitch is the calculated angle in which a roof is shaped. For example is a roof has a twelve-inch run with a rise of four inches the roof pitch will be a 4/12 or 4:12 pitch

Roof slope is often expressed as the pitch of the roof, however it is more closely described as the overall shape of the roof. Highly sloped roofs have a distinct style to a low-sloped roof. A low slope in a roof can often be seen in the form of a Flat Roof. Where a highly sloped roof will be seen as a more traditional Portland area shape, which has an attic, chimney, and includes an attic space.

Steep Roofs:

A steep roof pitch has many benefits, as well as additional costs to construct. In a wet climate such as Portland a home’s roof must be able to shed water, snow, and ice throughout the year. When a Portland roof sheds water it is performing properly in keeping the home dry. In areas with very heavy snowfall there are often even steeper “A” frame homes built to have a greater effect on shedding snowfall.

A steep roof pitch will provide useful interior space often used as an attic space in Portland homes. This attic space will require additional costs to construct. The attic space under the pitched Portland roof requires framing materials to build the shape and hold up the roofing materials. While there is an additional building cost, a pitched roof lasts much longer then a flat roof, requires much less maintenance, and stands up to water much better.

Flat Roofs:

Flat roofs are most often seen in commercial applications within the Portland area. A flat roof is cheaper to build, but requires constant maintenance, and is often prone to roof leaks. There is no attic within a flat roof, and therefore requires less energy to heat or cool the overhead space. With a heavy rain or snowfall the added weight placed on a flat roof will deteriorate the structure over time. Any time there is a pooling or gathering of water, a flat roof can be in danger of developing a roof leak. Since debris, and other materials will collect on a Portland flat roof constant cleaning and inspections are required.