All roofs can be divided into two slope types, steep and low. Low slope roofs have increased in popularity for residential homes due to their clean, modern design. They are also able to accomodate patios, porches, gardens and more. When choosing appropriate roofing materials for your project or deciding what type of structure to install, repair or replace, it is important to know and understand the difference between the two types.
Steep Slope Any roof with a slope of 25% or more is a steep slope. Steep slopes consist of five basic components.
Roof covering includes shingles, tile cedar shake, slate or metal and the underlayment that sits underneath this to protect the sheathing from the weather.
The board or sheet materials that are attached to the roof rafters that create the roofline is the sheathing. In order to remain structurally sound, the sheathing is covered by underlayment and roofing material.
Roof structure is the trusses and rafters that structurally support the roof sheathing. This is created by the framing of the roofline.
Flashing is installed at any point on the roof where there are vulnerable spots, such as joints, valleys, chimneys or vent. Flashing is used to prevent water seepage in these areas.
A critical component of overall roof design is drainage. Drainage must be considered when choosing the layout, slope and shape of any roof. It is necessary to ensure that water is shed from the roof without compromising the structure of the roof.
Low Slope Low slope roofs are usually “flat”, but are actually any roof that is between 0-24% sloped. Low slope roofs have the same five basic elements, but there are some differences in the details.
Low slope roof coverings usually consist of a single-ply membrane such as PVC, TPO, Modified Bitumen or E.P.D.M. Also common are “built up systems” composed of multiple layers of asphalt and sheet materials covered with a gravel coating. Other material options are also metal or spray foam. All of these materials do require an underlayment between the materials and the roof sheathing.
Roof sheathing found on low slope roofs is quite different from sheathing for steep slopes. Some structures do have basic wood boards like residential structures; however, you may also see gypsum, concrete, metal, tectum or other fibrous materials.
Low slope roof structures are conceptually the same as steep slope roofs. There are rafters, trusses and joists supporting the sheathing. The materials for these structures may be steel, wood or concrete rather than wood.
Flashing serves the same purpose to prevent water seepage at vulnerable spots on the roof and doesn’t differ much from a steep slope installation.
One of the most critical parts of a low slope roof is drainage. The basic design of a low slope roof does not shed water like a steep slope roof. Even the slightest incline as well as gutters, internal drains and downspouts can be advantageous and effective. Special design considerations must be made for truly flat roofs. Options such as stepped slope insulation may be a safer bet.
Regardless of the type or roof you choose to install, it should balance all five of these components. Texan Roofing Pros addresses each of these components when assessing roofing needs and discussing with our clients. The hidden components of a roofing system are just as important as the visual impact of the roof covering. Texan Roofing Pros would love to help you determine what type of roof is ideal for your structure. We offer FREE inspections and estimates! Contact Texan Roofing Pros today! We proudly serve the San Antonio, Austin and Rio Grande Valley areas.