The lighting reeler and Bombay door in the Sumner Theatre grid
The lighting reeler and Bombay door in the Sumner Theatre grid

What happens on the grid of the theatre?

In this regular feature, you ask the questions and we answer them. This week, Simon asks about a theatre term he’s heard: the grid – what is it, and how is it used?

By Frank Stoffels

Frank Stoffels is the Production Services Manager at Southbank Theatre, in charge of the operation of the Back of House (BOH) areas at the Lawler and Sumner Theatre. He answers Simon’s question about the grid.

The grid is a support structure of the fly system of theatrical rigging – typically comprising ropes and pulleys – that enables stage crew to quickly and safely ‘fly’ elements of the set and lighting (and sometimes even actors) into and out of place. A grid deck is indispensable in all theatres with a fly tower, as it provides flexible and invaluable access to those fly systems.

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The Sumner grid

In the Sumner Theatre, it is a permeable working surface located 20 metres above stage at the top of our fly tower. The grid provides us access to the overhead loft blocks, which support one or more lift lines of the Power Flying System, as well as to the positioning of the lighting reelers (which provide power to our lighting bars) and other rigging components required for MTC productions.

The grid floor is constructed from steel beams, spaced 170mm apart, that run down stage to upstage. This slatted floor allows the flexible steel-wire rope of the flying system to pass through; it also gives us the flexibility to lower chain hoists or lighting reelers through the grid floor.

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The Sumner Grid

The grid of the Sumner Theatre is unique in its design compared to most other theatres. It was specifically designed with the loft blocks sitting two metres above the grid floor, to provide clear floor access in the bays, which have been designed with trolleys that can safely take a 500kg load in any position. The grid also has an access door in the floor known as a Bombay door, which give us the ability to lower heavy items through the grid floor to the stage (and conversely to raise them from the stage).

A good example of what we can do with the Sumner grid, of the design challenges we can overcome, came on 2018’s Wild. We needed to provide two 2000kg points in the grid to allow us to tilt a room on the set – this is double the point load we’d normally anticipate, and it required the expertise of structural engineers as well the design and manufacture of bespoke clamps to achieve the required loading!

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Wild photo by Jeff Busby

The Lawler

The Lawler Studio does not have a fly tower, so it doesn’t have a traditional grid as such. Instead, the Lawler grid is made from 500mm box truss (steel boxes in cross sections) that is raised and lowered by chain hoists operated by a motor controller.

Have something to ask MTC? You can submit your question and next week it might be yours that we answer.

Published on 8 July 2020

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