Reasons Why Composite Deck Can Warp

M. John
Learn Decking
Why composite deck can warp

Installing ultra decking in your outdoor space can make your home more visually appealing. Composite decking has many benefits over wood; one of the many advantages is no warping. Which why many homeowners prefer installing composite decking in their homes. But does this mean composite decking will never warp? Some people have complained that their composite decking has warped. Can this be true? The short answer is yes; composite decking, in some rare cases, has warped. Warping of composite decking boards is mainly due to thermal expansion and incorrect installation.

We will explore why you may read about some people still complaining that their composite decking has warped. What are the reasons why composite decking warps?

What Causes Warping in Decking?

Reasons Why Composite Deck Can Warp


Heat can cause a deck to warp. When there are temperature changes, it can cause the decking to warp. Warping occurs when the decking’s surface is exposed to sunlight, causing the decking to become hot, which leads to thermal expansion.

Excessive heat can cause flexibility in composite deck boards, and when it cools, the decking shape can be distorted. If this occurs, the deck shape will not be straight and will look different.

Heat can cause a deck to warp. When there are temperature changes, warping occurs when the decking’s surface is exposed to sunlight. The decking becomes hot and starts to distort gradually.  It happens during thermal expansion when the decking absorbs heat from the sun and expands. What about composite decking? Can it warp too?

Will Composite Deck Warp?

Composite decking consists of wood and plastic material which differs from natural wood decking. As an engineered synthetic material, composite is known for its high durability compared with wood. Like almost all other decking materials, when exposed to high temperatures from the sun, composite decking will absorb heat. When this happens, composite decking becomes hot and flexible. Composite decking will not shrink like wood; it will only expand when hot. However, warping can occur if the installation is not performed correctly. What are the reasons for a composite board warp?

Reasons Why Composite Decking Can Warp

The reason wood-plastic composite (WPC) decking can warp during thermal expansion is when it is allowed to touch fixed surfaces or objects. For example, if the composite board touches a wall or gets too close to other boards, it will not be able to expand further, which leads to warping. Additionally, the tight squeezing of the entire composite decking area during thermal expansion can shift the boards from their original position and even remove them from the joists or substructure.

For more information on expansion and contraction gaps, please review the articles on board gaps during the installation of composite decking.

How to Prevent Warping in Composite Decking

In the first instance, buy higher-quality composite decking boards. Quality composite deck boards offer improved resistance to warping; if there is a change in temperature that causes composite decking to expand and there are no spacing or expansion gaps between the boards, warping can occur.

The way you install your composite decking will determine whether it will warp or not. Composite decking will not warp if you follow the manufacturer’s guidelines for correct installation.

Zero warp composite deck

Quality composite decks offer resistance to warping. When installing composite decking, ensure that the decking is appropriately spaced to allow it to expand freely. The gaps between the boards will prevent them from being tightly close to each other when it expands. When there is space between the composite board, the board will expand freely without warping.

To prevent warping, ensure the decking is fixed by a composite decking professional. Decking experts recommend leaving a space of 5 mm between the composite decking boards. In addition, a space of 15 mm is also recommended between composite decking and fixed objects such as walls and fencing.


The reason composite decking can warp is almost always due to poor installation. Mainly due to the lack of thermal expansion gaps or spaces between each composite decking board and fixed objects or surfaces. Pay close attention to the gaps and spaces to ensure composite decking boards can move freely during thermal expansion to avoid warping.

Also read, can composite decking overhang?


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