Roof Live Load Vs Dead Load

For example appendix a indicates that one type of clay tile roof system has a live load value of 20 psf and a dead load value of 15 psf.

Roof live load vs dead load.

The roof shall be designed for the live load indicated in table r301 6 or the snow load indicated. Dead loads depends upon the unit weight of the material. Dead loads are the permanent loads which are always present. R 1 1 for a t less than or equal to 200 psf r 1 1 2 0 001 a t for between 200 psf and 600 psf.

Dead loads includes the self weight of walls floors beams columns etc. On a roof with a slope greater than 4 to 12 the live load limit is typically adjusted downward from 20 psf to 15 psf to allow for the relatively greater dead load on the steeper roof. The might of the dead load or lack thereof often defines how much live load it can handle. Roof live load may be reduced by the following equation.

L r l o r 1 r 2. All loads are typically categorized into two types live and dead. As a result the live load dead load and distribution of forces are different. Dead loads are due to self weight of the structure.

Reinforced concrete creates the heaviest dead loads but also supports the most weight with its tremendous compressive strength. It is simply listed. Unlike the trussed roof live load and dead load of the rafters and ceiling joists must be accounted for as separate systems. The dead loads are permanent loads which result from the weight of the structure itself or from other permanent attachments for example drywall roof sheathing and weight of the truss.

Canpro the metal building company did not break the mezzanine loads into dead live. The metal building company does provide live load reactions but having inquired of this in the past i ve been informed that the live loads unless specifically stated otherwise refer to roof live loads. Ground snow load might seem somewhat confusing until you read the basic premise that is identified in irc section r301 6 which states. Roof live load reduction.

Where l r shall not be less than 12 psf and not more than 20 psf. Since it is possible to use the attic for storage the live load of the attic floor is set at 20 psf according to code. Af pa s appendix a lists a variety of live and dead load combinations for floors ceilings and rafters. Because live loads depend on structural strength knowledge of the exact planned use of the building is critical.

Victor staley a building official in the town of brewster mass responds. This issue of live load vs.