How To Fix Composite Deck Warping

Composite decking is a popular material for decks because it doesn’t warp, rot, or splinter like traditional wood decking. However…, it can still warp in certain conditions. In this post, we’ll look at the causes of it and the ways it can be repaired.

So if your composite deck is warping, there are a few things you can do to try to fix the problem. First, check to see if the warping is caused by an uneven surface. If the warping is not caused by an uneven surface, it may be caused by moisture. In this case, you can try to dry out the deck by opening up the space underneath it and/or using a dehumidifier. If the warping is severe, you may need to replace the affected boards.

A cautionary note though, fixing warped composite is doable for a small number of warped composite decking boards, but if the problem is too bad, you will need to go the full replacement route.

Composite Can Still Warp Despite What It Says On The Packaging!

Composite decking can still warp due to several factors, including:

  • thermal expansion
  • changes in moisture levels including inadequate draining under composite decks. This is more likely to occur in un-capped composite than capped composite.
  • The wood plastic composite decking is in contact with a fixed object on the deck, therefore not allowing it to move with the rest of the deck,
  • changes in the weather,
  • poor construction such as joist spacing being too far apart,
  • and an imbalance in the weight of the deck.

Thermal Expansion A Major Cause Of Warping

When there is a change in temperature, heat can cause wood decking to warp. This means that warping occurs when the surface of your timber decking is exposed to sunlight. The wood deck will become hot and gradually warp.

Most composites warp for this same reason of thermal expansion. This is the most common reason regardless if it is natural wood decking or composite.

When exposed to the sun, composite decking absorbs heat like other types of outdoor decking. When the deck becomes warmer, composite decking also undergoes thermal expansion.

It does matter what quality composite decking you get. The old adage that you ‘get what you pay for is very accurate with this issue. So if you can, choose a quality product such as Trex.

Inspect The Warped Deck To Determine Possible Causes

You may need professional help to work out what is causing the decking to warp, but it is worth having a look yourself to see if you can diagnose what is happening. Warping may be an issue if the joists are wet because water has been getting in under the decking, or if it has been less than a year since installation and the joists were not fully seasoned before they were used.

In either case, assisting ventilation and/or radiant heaters might dry out the deck for short-term use; however, this is only a temporary fix. The main culprit of warping in composite decks is moisture-induced warping from rainwater getting under the cracks and evaporating from within.

While railing eaves can help to keep water away from fragile surfaces such as wood (deck porch), they don’t always work well to protect lengthy runs of composite decking material.

Ways To Fix A Warped Composite Deck

Sometimes composite decking boards warp – they just do. If you’ve discovered that you have a warped deck, there are a few things you can do to try to fix it before resorting to the more drastic measure of replacing your composite board:

  • Firstly, inspect the warping boards and determine if they can be fixed with a simple repair.
  • If things are not too bad, you may be able to try to gently push the boards back into place using a straight edge and a hammer, then add screws to hold them down in place. 
  • If the warping is minor, you may be able to fix it by using a clamp or screws to straighten the board. With this method, use as many clamps as you need to secure the warped boards in place while you screw them down flat again.
  • Another method is to use a heat gun to heat up the warped boards and then bend them back into place.
  • You can also try using a power washer to clean the deck and remove any dirt or debris that may be contributing to the warping.
  • If that doesn’t work, you can also try using a heat gun or a blow dryer to warm up the deck and help it expand back into shape.

If those methods don’t work, you may have to remove and replace the affected boards. So if the warping is more severe, you will need to remove the screws from the bad board and then cut out a new piece of composite decking to replace it. Make sure that you use screws that are long enough to secure the decking in place.

Best way to repair warped composite decking – YouTube Aug 24, 2014 … My husband and I are building a new house and bought composite decking.

Prevent Further Warping

For permanent solutions, utilize tough sealant over application-specific gaps (examine joints with a large flashlight), make joint connections water tight.

Composite decks are composed of a top layer of its constituent materials fused together. There may be multiple other layers below it on the deck, such as plywood or cedar planks.

A rather extreme way to fix warping can be by removing the composite surface and replacing it with something more sturdy like wood slates or aluminum panels.


By following these tips, you can keep your composite deck warp-free for years to come.

We have some additional articles on composite decking on this site. You may like to check these out:

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