Green Roof Structural Engineering

Removing unnecessary finishes may provide sufficient capacity for a green roof of equal weight.

Green roof structural engineering.

Proper selection of agriculturally durable materials structural engineering design and review and responsible water handling should all be considered to achieve maximum energy efficiency and perhaps leed recognition. Soil does not necessarily occupy the full depth of the assembly. The allowable depth of the green roof is determined by the load capacity that can be allocated to it. With regard to green roofs the overriding issue is one of structural capacity to accommodate the additional loads.

A structural engineer s advice is essential to ensure comprehensive design development based on the building s construction condition and weight loading capacity. Being the structural engineer i need to account for the weight imposed on the roof by the system. The popularity of green roofs has risen in the united states over recent years as a result of several contributing factors. Incorporating gardens or other forms of green roof plantings can be an attractive alternative to traditional building construction.

Green roofs lessen the environmental extremes common on conventional roofs reduce storm water runoff increase energy efficiency and enhance the urban soundscape. For retrofitting a green roof wall or facade it is important to establish early whether the installation will meet the existing structural capacity of the building or whether this will be modified to support the installation. Waterproof membranes now make it easier to design green roof systems that capture water for irrigation allow drainage support the growing medium and resist the invasion of roots. Practices that capture and store rainfall in an engineered growing media that is designed to support plant growth.

The first conservative assumption by structural engineers is to use the full saturated weight of 110 pcf for the full depth of the green roof assembly. Modern green roofs typically use lightweight engineered soils with very light drainage and insulation layers. Currently the building is being proposed using a modular roof system. I have a client who is looking to place a green roof on top of a proposed single story commercial building.

Some roofs are finished with substantial architectural build ups such as concrete pavers or stone. This chapter considers the technical and engineering considerations that stakeholders need to take into account. At sullivan engineering llc we define green roofs as those roofs that contain vegetation also known as vegetative roofs.