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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

Mortar between masonry units consists of cement, lime, and sand. These materials are used in different mix proportions. For example, a lower strength mortar of this type would have a proportion 1:2:9 cement:lime:sand, and a higher strength mortar would have proportions of 1:1/2:3 1/2 cement:lime:sand. This mortar has a similar colour as cement:sand mortar. Lime is usually added to improve workability at the time of construction, but it does not improve strength.

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