Low Slope Roof Live Load

For dead loads you are correct.

Low slope roof live load.

Then apply standard asphalt shingles over the membrane. Steep slope roofs have the greatest pressures in the perimeter and corners as well as the roof peak and eaves. Residential low slope roofing can generally be divided up into two broad categories. 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.

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

To do this i use conservative too heavy dead loads and full snow loads regardless of pitch. Other geometric discontinuities may have increased pressures as well especially those at greater height on the structure. For a low slope residential roof there are two main options. And ice reduces a roof s snow load and dries more quickly than a light colored roof.

For low slope roofs wind pressures typically have the greatest magnitude at the roof perimeter and corners. Where deflection from snow or other live loads is a concern a greater slope will be needed to prevent any ponding. 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. Therefore a roof designed and installed to a 1 4 in 12 slope deflects downward and needs to be analyzed as a susceptible bay according to asce 7 10.

Resilient synthetic rubber membrane widely used on low slope roofing projects for over 50 years in the united states and worldwide. The membrane will outlast the shingles and seal around all nail penetrations. 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. 1 cover the entire surface with a self adhesive flashing membrane such as grace ice water shield there are many equivalent products.

Installation is important when it comes to putting a single ply roofing system on a building. However in my practice i typically use the horizontal run of the roof for both types of load.