What is thermal expansion?

We don’t need to get into the science of thermal expansion. It’s enough to know that metal will expand when exposed to the heat of the sun – and will contract in the winter.

What you do need to know, however, is that thermal expansion creates a challenge for rainscreen cladding, architectural façades and brise soleil projects. Naturally, façade and brise soleil specialists will take this into account when designing and installing panels and blades. But architects and contractors should be aware of it too.

The most important thing to remember is that specifying perfectly flush joints is not practical (nor necessary, because rainscreen cladding is not a sealed system) and that tolerances need to be built in for expansion. Typically, this will amount to around 3mm between panels, but may be larger or smaller depending on the size of the panels.

For brise soleil projects, thermal expansion will have a cumulative effect over the length of the blades. Longer spans will expand more in total. As a rule of thumb, specialists will design a 1mm gap into every 1m of brise soleil.

The thermal expansion of panels and blades will have an impact on the design of the support structure too. That’s why façade specialists liaise closely with steelwork contractors from Day One.

However, these days, it’s more common for façade specialists to factor ALL tolerances into ONE consistent design detail. So, not just gaps for thermal expansion but also steelwork tolerances, manufacturing and installation tolerances, and ‘live load’ tolerances, which take into account the movement of a building (say, a car park).

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