Does Composite Cladding Expand?

Before we answer the question, ‘does composite cladding expand?’, let’s look at how it differs from wood. The trouble with timber cladding is that it’s made from wood! This means it absorbs water, which causes it to twist, warp, crack and eventually rot. Even the best kept timber cladding will eventually succumb to the elements to the inherent properties of wood.

So, before you rush out and buy a timber alternative you probably have a few cladding questions. Quite natural for you to question the performance of composite cladding so let’s get down to brass tacks, does composite cladding expand and contract?

Like almost all materials, composite cladding does expand. But wait, before you check out and abandon it as an option, cladding is supposed to expand! In fact, we have designed it to expand. When exposed to heat, material like wood, plastic and even steel expand and as they cool, they contract. Through a process of thermal expansion, the bottom deck of the “Golden Gate Bridge” in San Francisco has been seen to rise and fall by a difference of 16 feet between hottest and coldest days. Similarly, care should be taken when installing your composite cladding to ensure adequate expansion gaps are observed.

Composite cladding, like all composite materials, is made from a 60/40 split of wood fibres and plastic polymers. Wood expands and contracts by a lesser degree, plastic however responds more to temperature range and so thermal expansion is greater. For this reason, we always recommend installing cladding boards with a gap when butting two pieces together – what gaps are left depends on the outside temperature at the time of installation. These gaps provide ample space for the boards to expand and contract as temperatures fluctuate.

Just like our decking, composite cladding expands and contracts to a greater degree than timber so we always recommend allowing boards to acclimatise initially. When accepting delivery, follow the cladding installation guide on how far apart they should be installed, according to the temperature on the day of install, allowing expansion gaps at butting ends and drilling pilot holes when fixing through the boards into the battens. Doing so will allow the boards space to breathe naturally without knocking against other boards or pulling at the cladding screws which expand to a far lesser degree.

Because composite cladding is designed to expand and contract naturally it is not vulnerable to the kind of damage which timber sustains. Engineered to resist moisture absorption, it is protected against the usual issues that timber is affected by. Warping, cracking and rotting do not occur with composite cladding (if installation is followed correctly). Traditional composite cladding provides 99% protection against moisture damage and second-generation capped composites offer even more.