Planning a roof replacement involves taking many factors into consideration: the roofing slope, the type of material and local environmental factors, among others. Another important but not-as-discussed factor is roofing loads.
What Are Roofing Loads?
Roofing loads are forces both permanent and temporary that exert pressure on the roof. The limit of the load a roof can support is determined by factors, such as the design of the roof itself, snowfall, average wind speed and the combined weight of the roofers who will be working on the roof. Calculating the roofing loads beforehand can help make sure the roof will withstand external pressure during and after installation.
Types of Roof Loads
The following are some of the most common types of anticipated roof loads:
Dead load – The dead load is the combined weight of the roof and permanent structures like dormers and chimneys. A standard asphalt shingle roofing system usually has around 15 pounds per square foot (psf) of dead load. Roofs with heavier materials would have a higher dead load. For example, a clay tile roof can have as much as 27 psf dead load.
Live loads – Live loads are the weight of temporary objects on the roof, such as rainwater, snow or roofers working on the roof. A completed roofing structure must be built to support the sum of both dead load and anticipated live loads. A typical expected live load on a roof is about 20 psf. Therefore, our asphalt shingle example from above should be able to support at least 35 psf.
Uplift load – When high winds hit the side of the building, it gets dispersed both upward and downward. The wind that blows upward exerts an uplift load that the roof must resist. The standard load limit is about 90 miles per hour (mph) with about 20 psf uplift load.
Slope correction – The steeper the roof, the more weight will be exerted on the roof’s horizontal framing. This is why the roof slope has to be corrected to meet the minimum load-bearing requirements per applicable building codes. This is important when a heavier type of roofing material is going to be installed on the roof deck.
Superior Roofing is your leading provider of roof repair and installation services. Give us a call at (706) 862-8008, (334) 869-7433 or (334) 218-5965. You can also fill out our contact form to schedule an appointment. We serve customers in Phenix City, AL, and the surrounding communities.