Low Slope Roof Truss Design

The run or the base number is 12 inches.

Low slope roof truss design.

Pitch slope the pitch or slope is the incline of the roof expressed as a fraction describing the rise over the run. Classification of low slope roofing. Epdm won t last as long as metal but there s a reason it s the most common roofing for very low slope roofs. Another approach is to build a cupola or ventilated doghouse in the middle of the low slope roof an approach championed by joe lstiburek.

It is out of these categories. Low pitch large span and high wind speeds and this is where you ll find a truss working the hardest. On low slope roofs in the snow zone epdm will be work better than standing seam since it can t leak even under high winds whereas metal roofs will. Design professionals frequently specify the minimum code permitted slope with little if any consideration of the resultant valley slope created by the intersecting planes figure 1 ponding water is commonly observed at valley intersections for low slope roof and deck.

It is a common roof on sheds and other outbuildings and is frequently used on carports patios porches and small additions to a house. This can be cantilevered at one or both ends. While this article focuses on configurations we also have a very cool set of illustrations showcasing the different parts anatomy of roof trusses. There are three factors that most affect the strength of low pitch trusses.

If the upper edge of a low slope shed roof intersects a vertical wall the most logical approach in my opinion is to detail the roof as an unvented roof. Understanding low pitch roof truss design. With limited slope to drain well it can take forever to be rid of any leakage moisture. A roof that slopes in only one direction is called a shed or pent style.

Just as there are many types of roofs with many roof parts there are many different types of roof trusses this extensive article explains through a series of custom truss diagrams the different truss configurations you can use for various roofs. Combine these three at their most extreme i e. The flat truss can be designed as bottom or top chord bearing or for multiple and simple spans. It also is often used on dormers extensions built on a basic roof to provide more light or space inside.

A flat truss is not necessarily flat as it slightly slopes to prevent the pooling of water on the roof and prevents the damaging or collapsing of the entire structure. A low slope roof design typically has a pitch of between 2 12 and 4 12. Specifically the code text typically reads roofs shall have a design slope of not less than one fourth unit vertical in 12 units horizontal 2 percent slope for drainage the stated and intended purpose of the code specified 1 4 in 12 slope is to provide drainage. According to low slope roof definitions low slope roofing can be classified into five main categories.

However ponding water is often observed in these low slope roofs. For example a slope of 6 12 means for every 12 inches of horizontal distance the slope of the roof will rise 6 inches vertically. Just like any other roofing system low slope roof designs will have several effects on the overall construction of the building including the interior volume the style and design of the house the drainage system and the material used for covering.