Green Roof Structural Engineering

The popularity of green roofs has risen in the united states over recent years as a result of several contributing factors.

Green roof structural engineering.

A portion of the captured rainfall evaporates or is taken up by plants which helps reduce runoff volumes peak runoff rates and pollutant loads on development sites. This chapter considers the technical and engineering considerations that stakeholders need to take into account. 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. Removing unnecessary finishes may provide sufficient capacity for a green roof of equal weight.

Practices that capture and store rainfall in an engineered growing media that is designed to support plant growth. 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. Soil does not necessarily occupy the full depth of the assembly. Green roofs lessen the environmental extremes common on conventional roofs reduce storm water runoff increase energy efficiency and enhance the urban soundscape.

A structural engineer s advice is essential to ensure comprehensive design development based on the building s construction condition and weight loading capacity. I have a client who is looking to place a green roof on top of a proposed single story commercial building. The proposed depth of the system is 5. Currently the building is being proposed using a modular roof system.

Modern green roofs typically use lightweight engineered soils with very light drainage and insulation layers. 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. Some roofs are finished with substantial architectural build ups such as concrete pavers or stone.

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. Green roofing the term green roofs has taken on several different meanings in recent years. Incorporating gardens or other forms of green roof plantings can be an attractive alternative to traditional building construction.