Roofing continued:
Just like the rest of the house, the roof starts out as a frame. The frame is usually constructed of joists, trusses, and rafters. Together, these three types of beams make up a framework that gives the roof its shape and strength to support the weight of the roof plus snow if applicable. Asphalt shingles are standard roofing materials, but if you plan to use heavier materials like tile or slate, you may need to add extra supports at this stage. Once the frame is in place, it is covered in decking (like sheathing on a wall but usually stronger). Decking is the skin that covers the frame and creates the base that the rest of the roof will be built upon. The most common material for decking was once plywood. However, in recent decades oriented strand board (OSB) has taken over as the most common material for load-bearing planks in residential construction. OSB is similar to particle board, but instead of tiny bits of wood, it is made up of thin strips of wood. The strips are held together with resin and a small amount of wax to form a very strong plank. The first water barrier layer of the roof is the underlayment. Underlayment is installed directly on top of the decking. Mainly, it serves as a back-up water barrier in case any water makes it past the shingles. In cold climates, roofs may have an additional special underlayment that acts as a water and ice barrier. It can help protect from ice dams that form when the bottom layer of accumulated snow melts and refreezes at the edge of the roof. Some of these underlayments may have special properties such as being self-adhering and closing around nails for a watertight seal. In cold climates and areas prone to driving rain and high winds from hurricanes, the water and ice barrier might cover the whole roof. In more mild climates, ice and water barriers may still be used in vulnerable areas of the roof, like valleys, roof edges, and around penetrations in the roof. After the underlayment is installed, flashing is installed in areas of the roof that collect a lot of water. Valleys, where water from multiple roof planes is directed into a gushing stream, are always covered with flashing. The flashing is generally a thin layer of sheet metal that protects a vulnerable joint and directs water away from the area. Flashing is also used anywhere the decking is cut open for some type of penetration. For example, a chimney/dormer requires flashing all around it. The final outermost layer of the roof is the shingles or rubber roof. It is the part of the roof that is visible. The most common type of shingles are asphalt shingles due to their relative ease of installation, asphalt shingles will melt to each other in the hot sun when installed properly. Other common roof coverings are stone-slate shingles or metal roofing. Rubber roofing is used when a roof pitch is less than 3, because water will not drain fast enough on a flat roof.
Just like the rest of the house, the roof starts out as a frame. The frame is usually constructed of joists, trusses, and rafters. Together, these three types of beams make up a framework that gives the roof its shape and strength to support the weight of the roof plus snow if applicable. Asphalt shingles are standard roofing materials, but if you plan to use heavier materials like tile or slate, you may need to add extra supports at this stage. Once the frame is in place, it is covered in decking (like sheathing on a wall but usually stronger). Decking is the skin that covers the frame and creates the base that the rest of the roof will be built upon. The most common material for decking was once plywood. However, in recent decades oriented strand board (OSB) has taken over as the most common material for load-bearing planks in residential construction. OSB is similar to particle board, but instead of tiny bits of wood, it is made up of thin strips of wood. The strips are held together with resin and a small amount of wax to form a very strong plank. The first water barrier layer of the roof is the underlayment. Underlayment is installed directly on top of the decking. Mainly, it serves as a back-up water barrier in case any water makes it past the shingles. In cold climates, roofs may have an additional special underlayment that acts as a water and ice barrier. It can help protect from ice dams that form when the bottom layer of accumulated snow melts and refreezes at the edge of the roof. Some of these underlayments may have special properties such as being self-adhering and closing around nails for a watertight seal. In cold climates and areas prone to driving rain and high winds from hurricanes, the water and ice barrier might cover the whole roof. In more mild climates, ice and water barriers may still be used in vulnerable areas of the roof, like valleys, roof edges, and around penetrations in the roof. After the underlayment is installed, flashing is installed in areas of the roof that collect a lot of water. Valleys, where water from multiple roof planes is directed into a gushing stream, are always covered with flashing. The flashing is generally a thin layer of sheet metal that protects a vulnerable joint and directs water away from the area. Flashing is also used anywhere the decking is cut open for some type of penetration. For example, a chimney/dormer requires flashing all around it. The final outermost layer of the roof is the shingles or rubber roof. It is the part of the roof that is visible. The most common type of shingles are asphalt shingles due to their relative ease of installation, asphalt shingles will melt to each other in the hot sun when installed properly. Other common roof coverings are stone-slate shingles or metal roofing. Rubber roofing is used when a roof pitch is less than 3, because water will not drain fast enough on a flat roof.