Expressing Building Movement

Building movement is often a complex, and scary consideration when designing a building. Get it wrong and it could be very costly! One famous (and expensive) example of this is the Guggenheim museum in New York. The Architect (Frank Lloyd Wright) didn’t install expansion joints, leading to a $29million restoration project back in 2007! Yikes!

So, to help you along the way we thought we would take the time to explain the different ways building movement can be conveyed so that when you come across it, or have to do something with it, you understand what you’re looking at.

So, lets take a look at a simple approach to joint movement:

Nominal Joint Width
The nominal joint width is the size of the gap at the start (before any movement has occured)

Minimum Joint Width
The Minimum joint width is the smallest width the gap will become. 

Maximum Joint Width
The maximum joint width is the largest width the gap will be opened up to.

So, with those figures you can calculate the amount of movement that’s going to occur, but how do you express that movement?

Anticipated movement can either be expressed as a total or overall movement, as a percentage of the expansion joint width or, more usually, as a +/- movement.

There is no right way to do it, different architects, engineers and manufacturers express it in different ways, but it’s important to understand what each one means. If you interpret it wrongly it could be very costly!

For example:

50mm nominal expansion joint with an anticipated expansion and contraction of 25mm could be expressed as: