Roof Design Loads

The amount of weight a truss needs to support per square foot is important.

Roof design loads.

Framing table for maximum roof rafter spans. Loads used in design load equations are given letters by type. In commercial or industrial buildings for each floor or portion thereof designed for live loads exceeding 50 psf 2 40 kn m 2 such design live loads shall be conspicuously posted by the owner or the owner s authorized agent in that part of each story in which they apply using durable signs. Chapter 3 design loads for residential buildings.

This includes all of the roofing material and ceiling along with loading for construction purposes and then environmental factors such as wind and snow. 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. 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. 50 psf x 14ft 700 pounds per lineal foot.

910 pounds per lineal foot. This means that one is a fixed node and the other is a rolling node. 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. 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.

For a larger map with greater detail refer to asce 7 98. 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. Roof load live load design is affected by the shape of the roof whether it is flat curved or pitched. 15 psf x 14ft 210 pounds per lineal foot.

Roof loads are a downward vertical force on the home. This downward imposed load on the home is also known as the snow load. D dead load l live load l. 3 20 residential structural design guide.

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. The north zone middle zone and the south zone are identified on the roof load zone map above.