When planning a roof installation, the roofing company needs to consider many factors: slope, material and even the average rainfall amount in the local area. In this blog, Winfield Builders discusses another factor that isn’t discussed as often, yet is nevertheless essential: roof loads.
What Are Roof Loads?
Roof loads include both permanent and temporary forces that exert pressure on the roof. The limit of the load the roof can support is largely determined by its design. When designing a roof, a roofing contractor takes into consideration factors such as average wind speed, snowfall amounts and even the weight of the people who will be working on it. Calculating the right roof load helps make sure that the roof will be able to withstand such conditions.
Types of Roof Loads
The following are some of the commonly anticipated roof loads:
Dead Load — The dead load is the weight of the roof itself, along with permanent structures such as chimneys and dormers. A typical asphalt shingle roofing system has 15 pounds per square foot (psf) of dead load. By comparison, a clay tile roof has as much as 27 psf of dead load.
Live Loads — Live loads are the weight of any temporary objects on the roof. This includes snow, rainfall and roof installers. The roofing structure must be able to support the sum of the dead load and anticipated live loads. A typical expected live load is about 20 psf. Therefore, the asphalt shingle roof in our earlier example should be able to support at least 35 psf.
Uplift Load — High winds that hit the side of the building are dispersed upward and downward. The wind that shifts an upward direction exerts an uplift load that the roof should be able to resist. The standard load limit is about 90 miles per hour, with a load of about 20 psf. Most of the uplift load will be resisted by the roof’s dead load.
Slope Correction — A steeply sloped roof will have more weight pushing on a horizontal surface; therefore, the roof slope may need to be adjusted to meet the minimum load-bearing requirements in the local building code. This is important when a different type of roofing material will be installed, or if changes need to be made for code compliance.
Winfield Builders is your leading provider of roofing and siding services. Give us a call at (301) 329-8295 or (410) 401-5045. You can also fill out our contact form. We serve customers in Annapolis and Columbia, MD.