Roof Design Loads

In order for a roof truss load to be stable you need to assign two of your nodes on each truss to be support nodes.

Roof design loads.

Roof loads are a downward vertical force on the home. 50 psf x 14ft 700 pounds per lineal foot. A fixed node will provide support in both directions down the length of the roof truss members often called the x and y directions. This means that one is a fixed node and the other is a rolling node.

For a larger map with greater detail refer to asce 7 98. The amount of weight a truss needs to support per square foot is important. The north zone middle zone and the south zone are identified on the roof load zone map above. Loads used in design load equations are given letters by type.

The dead load on a roof is the weight of the roof structure itself along with any permanently attached materials or structures on the roof so it must be designed first of all to support itself. Depending on your region you may need to design for a maximum snow load of anything between zero to 65 pounds per square foot or roughly 0 3 kpa. Let s look at the sample table below which shows maximum rafter spans for a snow load of 31 3 pounds per square foot psf. It is important to list live load dead load and total load separately because live load is used to compute stiffness and total load is used to calculate strength.

3 20 residential structural design guide. 15 psf x 14ft 210 pounds per lineal foot. Live roof load w wind load s snow load e earthquake load r rainwater load or ice water load t effect of material temperature h hydraulic loads from soil f hydraulic loads from fluids. Roof load live load design is affected by the shape of the roof whether it is flat curved or pitched.

D dead load l live load l. Chapter 3 design loads for residential buildings. In areas where the ground snow load is less than 15 psf the minimum roof live load refer to section 3 4 is usually the controlling rgavity load in roof design. Framing table for maximum roof rafter spans.

This downward imposed load on the home is also known as the snow load. 910 pounds per lineal foot.