Griund Versus Roof Load

Victor staley a building official in the town of brewster mass responds.

Griund versus roof load.

Ground snow load or roof snow load snow load. The roof shall be designed for the live load indicated in table r301 6 or the snow load indicated. Economical structural design in these areas requires an accurate prediction of the ground snow plus an understanding of how the snow is distributed on the roofs. Length of roof upwind of the snow drift.

1 0 importance factor i. When discussing snow load with anyone it is crucial to have a clear understanding as to if the load is a ground or flat roof snow load. It s quite easy to find one online. The truss could be designed based on the assumption that the 25 psf roof snow load is a factored ground snow load in which case a ground snow load is back calculated using asce 7 based on the specified roof snow load pg 25 psf therein lies the problem with specifying only a roof snow load.

Enter the information requested like the rise and the roof ground snow load for your city exposure roof type etc. 1 0 exposure factor ce. Ground snow load might seem somewhat confusing until you read the basic premise that is identified in irc section r301 6 which states. Roof loads are a downward vertical force on the home.

The north zone middle zone and the south zone are identified on the roof load zone map above. Figure 7 1 pages 84 85 and table 7 1 page 92. 70 60 50 40 35 30 25 x0 7 x0 7 x0 7 x0 7 x0 7 x0 7 x0 7 roof snow load. This downward imposed load on the home is also known as the snow load.

Pf is flat roof snow load if as a consumer your concern is snowfall and you want to upgrade the ability of your building to carry it this is the value to increase. The calculator will tell you the pounds per square foot of snow. Length of high roof lu. 49 42 35 28 24 5 21 17 5 assumed value thermal factor ct.

The flat roof snow load is calculated using formula 7 3 1. The snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load. If you live in the us our snow load calculator compares the total weight on your roof with the permissible load calculated according to the standards issued by the american society of civil engineers regarding the minimum design loads for buildings and other structures asce7 16. After that you ll need to use a snow load calculator.

Weight of permanent. Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10. Roof load live load design is affected by the shape of the roof whether it is flat curved or pitched. Snow loads can be presented in two different ways.

In our case let s assume that our structure has a flat roof roof slope 5. Sheikh taheri snow loading is the most severe test of roof structures in many parts of the state of idaho. The determination of the drift load that is. This issue of live load vs.

Table 1 1 page 3.