Low Slope Roof Live Load

For low slope roofs wind pressures typically have the greatest magnitude at the roof perimeter and corners.

Low slope roof live load.

However in my practice i typically use the horizontal run of the roof for both types of load. 1 cover the entire surface with a self adhesive flashing membrane such as grace ice water shield there are many equivalent products. And ice reduces a roof s snow load and dries more quickly than a light colored roof. To do this i use conservative too heavy dead loads and full snow loads regardless of pitch.

Minimum slope for low slope roof systems with any roofing material a slope of at least 1 4 inch per foot is recommended to promote drainage and minimize ponding. The 1 4 in 12 design slope is reduced more from live load and long term dead load creep to exacerbate water retention. For example in the rafter span table below the highlighted cell in the 40 live load table indicates that 2 x 8 southern yellow pine joists that have a grade of 2 that are. Residential low slope roofing can generally be divided up into two broad categories.

Installation is important when it comes to putting a single ply roofing system on a building. Technically you should use the actual rafter length when adding up the weight of roofing materials. For a low slope residential roof there are two main options. Larger flat roofed applications low slope such as residential condominium complexes row homes and town houses and smaller applications such as residential porch and garage transitions from the main home where the slope of the roof changes dramatically.

Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run. Other geometric discontinuities may have increased pressures as well especially those at greater height on the structure. The membrane will outlast the shingles and seal around all nail penetrations. Resilient synthetic rubber membrane widely used on low slope roofing projects for over 50 years in the united states and worldwide.

For dead loads you are correct. On a roof with a slope greater than 4 to 12 the live load limit is typically adjusted downward from 20 psf to 15 psf to allow for the relatively greater dead load on the steeper roof. Then apply standard asphalt shingles over the membrane. Where deflection from snow or other live loads is a concern a greater slope will be needed to prevent any ponding.

Finding the right products for your low slope roof. Self adhesive flashing membrane under the shingles prevents leakage on low slope roofs.