Low Slope Roof Rain Load

Many studies on roofed structures have been performed in the past.

Low slope roof rain load.

To do this i use conservative too heavy dead loads and full snow loads regardless of pitch. For dead loads you are correct. Many roofing shingles do not allow applications onto roofs at this pitch. More commonly roll on membranes such that use heat to bond seams together is used as a roofing material.

Uses the least amount of roofing material. We construct our residential style roofs at a minimum slope of several inches to the foot pitched to external gutters that have been sized to meet building codes. Codes prescribe a minimum slope of 1 4 in. Low slope roofs are often more susceptible to leaks.

Of two roofing manufacturers general manager of a roofing contracting company and for the past 34 years has been a consulting engineer roof consultant. Roof shape and slope are both important parameters for the safety of a structure especially when facing wind loads. Easy to access and. A structural member designed and installed to a 1 4 in 12 design slope deflects under the initial short term dead load to create a roof surface slope less than 1 4 in 12.

I ignore the slope. Low slope roofs i e roofs with slopes less than 1 2 inch of vertical rise for every 12 inches of horizontal run 1 2 12 are common in commercial and multi family projects including wood frame. A low pitched roof is anything that is any roof with a pitch of 3 12 or less. Per ft while the nrca calls for no ponding water on the roof 48 hours after a rain during conditions conducive to drying roofing manufacturers have their own requirements.

That shouldn t mean much to the roofing industry. Rain totaled 8 inches at new york s jfk airport 5 inches in philadelphia and 11 inches in seabrook farms nj. Rain also can add to snow loads on low slope roofs. Patterson has coauthored.

The 1 4 in 12 design slope is reduced more from live load and long term dead load creep to exacerbate water retention. This is because water tends to be stagnant on a flatter surface of a low pitched roof as compared to high pitched ones that lets the water flow freely downward. The framing members that support snow loads also resist the forces of rain loads. However in my practice i typically use the horizontal run of the roof for both types of load.

Roof design and practice published by pearson inc drainage design published by the rci foundation and. Wind pressures on low slope roofs published by the. For these projects rain and ponding loads should be a design criteria and when appropriate factored into the roof design loads.