Constructing a major new concrete building is a messy and complicated process, but one particular piece of equipment helps make the procedure a lot smoother; to construct concrete walls and floor slabs, the liquid material must be poured into a mould. Also known as formwork, these pieces are specially assembled to fit the needs of each part of a construction project… but it there is repetition from floor to floor, fly forms — or table forms — can be used again after the liquid concrete has cured from a previous pour. 

Plenty of fly forms and table forms in use to build lower levels of Galleria 1 and 2 in Toronto, image by UrbanToronto Forum contributor AlbertC


When dealing with simpler floor layouts, usually above the more complicated ground floor or garage levels, trusses are assembled and covered with plywood. Layers of steel rebar are then placed to sandwich any electrical and mechanical lines atop the plywood, and concrete is poured to cap the floor. Once the concrete cures, sections of the truss are released and the whole form can then be pulled out, initially by the crew, and then attached to cables and hoisted — or flown, hence the term 'fly form' — by the tower crane, to repeat the job again on the next level above.

Fly forms being repositioned by the tower crane, image by Marcus Mitanis

To ensure strength for the new floor while the concrete continues to cure to its full strength, temporary shoring jacks are installed for a few more weeks. The image below shows two Toronto projects, INDX Condos and EY Tower, both utilizing the fly form technique. Yellow shoring poles are visible on the top floors below the uppermost level with its fly forms, helping support the work above. 

Fly forms being used in two Toronto projects, image by Marcus Mitanis

Have any other construction and development related terms that you would like to see featured on Explainer? Share your thoughts and questions in the comments section below!

* * *

From 2015 to 2017, UrbanToronto and its sister publication, SkyriseCities, ran an occasional series of articles under the heading Explainer. Each one took a concept from Urban Planning, Architecture, Construction, or other topics that often wind up in our publications, and presented an in depth look at it. It's time to revisit (and update where necessary) those articles for readers who are unfamiliar with them. While you may already know what some of these terms mean, others may be new to you. We are publishing or updating and republishing Explainer on a weekly basis. This article is an update of one that first appeared in 2015.

* * *

Do you have other planning terms that you would like to see featured on Explainer? Share your comments and questions in the comments section below!

* * *

Want to read other Explainers? Click on the magenta Explainer box at the top of the page.

* * *

UrbanToronto has a research service, UrbanToronto Pro, that provides comprehensive data on construction projects in the Greater Toronto Area—from proposal through to completion. We also offer Instant Reports, downloadable snapshots based on location, and a daily subscription newsletter, New Development Insider, that tracks projects from initial application.