Rain Loading Configuration On A Roof

The accumulation of water caused by the deflection of the roof structure is called ponding and as it results in added load it can lead to roof instability.

Rain loading configuration on a roof.

3 2 load combinations the load combinations in table 3 1 are recommended for use with design. Until recently floor live load roof live load roof snow load wind load earthquake design data and flood loads were required to be listed on the construction documents. This is all of the natural stresses imposed upon a roof such as snow loads rain loads and wind loads. 1611 1 design rain loads each portion of a roof shall be designed to sustain the load of rainwater that will accumulate on it if the primary drainage system for that portion is blocked plus the uniform load caused by water that rises above the inlet of the secondary drainage system at its design flow.

Note that although rain loads are covered in ibc section 1611 they were not required to be listed on the construction documents. Sloped or not each segment of the roof shall be capable to carry the loading created due to blockage of the primary roof drainage system of that segment plus the load caused by water that rises above the inlet of the secondary drainage system at its design flow rate. This is highly regional as weights of snow for example range from 10 to 300 pounds per square foot based on moisture and volume of the snow. The key to managing rain loads in buildings is roof drainage including a primary drainage system and a secondary drainage system which is set at an elevation higher than the primary system to drain any water that builds up after the lower system is blocked or not working.

Note that although rain loads are covered in ibc section 1611 they were not required to be listed on the construction documents. Should your roof installation have to be delayed due to poor weather be patient. D s depth of water on undeflected roof up to the inlet of the secondary drainage system. Each portion of a roof shall be designed to sustain the load of rainwater that will accumulate on it if the primary drainage system for that portion is blocked plus the uniform load caused by water that rises above the inlet of the secondary drainage system at its design flow.

It is not the fault of your contractor and while the delays can certainly be frustrating a contractor who attempts to install a new roof in the rain is going to be compromising the overall integrity of the installation. Special loads such as flood loads ice loads and rain loads are not addressed herein. Until recently floor live load roof live load roof snow load wind load earthquake design data and flood loads were required to be listed on the construction documents. Nominal loads is essentially unaffected.

Asce 7 says that the rain load is 5 2psf in h s h d. The event that shall be considered is an intense short duration rainfall.