Green roofs typically use lightweight engineered soils with very light drainage and insulation layers.
Green roof dead loads.
For a green roof wall or facade the loads that the building structure must support include.
1 2d 1 0w l 0 5 l r or s or r 5.
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.
Or s or r included with the same load factor as 3.
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 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.
1 2d 1 0e l 0 2s when h loads are present they shall have 6.
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.
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.
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.
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 values for dead loads in table 3 2 are for commonly used materials and constructions in light frame residential buildings.
0 9d 1 0w a load factor of 1 6 when adding to load 7.
Soil does not necessarily occupy the full depth of the assembly.
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.
0 9d 1 0e effect or 0 9 when resisting the load when permanent.
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.
Astm e2397 is the established standard procedure for determining the dead and live loads associated with green roof systems.
Saturated with water the weight can increase by as much as 35 to around 100 to 110 pounds per cubic foot.
