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Glossary for gem taxonomy

Authors: Luke Allen, Andrew Charleson, Svetlana Brzev, and Charles Scawthorn

This online Glossary explains around 400 terms contained in the GEM Building Taxonomy v 2.0 and nearly 700 images.

The terms have been listed in alphabetical and numerical order. Text description of each term is accompanied by illustrations (photos and/or drawings) where possible.

We welcome contributions in the form of photographs or images, illustrating glossary terms. If you have any questions you can also contact us at

The general classification of the material of the roof system. Roof system is the structure that supports roof covering and environmental loading (such as rain and snow). Roof system is often not exposed from the exterior of the building. The material of roof system is usually different from the material of roof covering.

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