Green Roof Dead Loads

Dead load the final constructed weight of all built elements and all components associated with the roof or wall assembly including plants growing substrate and any water held in the system.

Green roof dead loads.

The dead load of a green roof assembly should be determined on a project specific basis because growth medium composition varies from job to job. Structural loads weight of green rooftops one cubic foot of dry agricultural dirt or loam typically used for a green roof weighs between 75 and 81 pounds. 1 4 this practice does not address point or line loads associated with architectural elements that are not essential components of a particular vegetative green roof system. The values for dead loads in table 3 2 are for commonly used materials and constructions in light frame residential buildings.

0 9d 1 0e effect or 0 9 when resisting the load when permanent. As noted in the draft astm standard standard guide for selection of roofing waterproofing membrane systems for vegetative green roof systems the introduction of a vegetative roof system to a new or existing structure has an effect on both the live and dead loads. The difference in weight between the first and second conditions approximated by the weight of transient water in the drain layer is considered a live load. For a green roof wall or facade the loads that the building structure must support include.

3 3 dead loads dead loads consist of the permanent construction material loads comprising the roof floor wall and foundation systems including claddings finishes and fixed equipment. Green roofs typically use lightweight engineered soils with very light drainage and insulation layers. 1 2d 1 0e l 0 2s when h loads are present they shall have 6. Astm e2397 is the established standard procedure for determining the dead and live loads associated with green roof systems.

The second most common conservative assumption found in the industry is to assume that the green roof is a soil load rather than a dead load. Saturated with water the weight can increase by as much as 35 to around 100 to 110 pounds per cubic foot. 1 2d 1 0w l 0 5 l r or s or r 5. 0 9d 1 0w a load factor of 1 6 when adding to load 7.

1 2d 1 6 l r or s or r l or 0 5w dead load d in 1 through 5 and 7. Soil does not necessarily occupy the full depth of the assembly. The addition of materials over the roofing waterproofing membrane system associated with vegetative roof systems usually increases the dead load in varying amounts based on the number composition and thickness of the layers.