One of the many attributes of composite decking is its strength and durability. Created as a superior alternative to wooden decking, it is unlikely that your composite decking will experience cracking when installed and maintained accurately. However, in some rare instances, cracking may occur due to being placed under immense weight and pressure, inaccurate cleaning or maintenance that weakens the boards or improper installation that is affected by thermal expansion. Nonetheless, you will, of course, want to know how to fix cracked decking if this problem occurs.

What Might Cause Cracking?

  • Heavy objects: Although extremely strong, if composite decking boards are consistently put under pressure from large, heavy objects, this can cause cracking and damage the structural integrity of the boards.
  • Chemicals: If you use harsh chemicals or bleach products on your decking when cleaning, this can alter the structural integrity of the board and weaken it, which can lead to cracking.
  • Improper installation: If you haven’t installed your composite decking with the accurate thermal expansion gaps necessary, the boards can butt together, causing warping and cracking. This can also be said for improper installation of the subframe below. Ensure all gaps are kept side to side and end to end of the boards to prevent this. 

Fixing Cracked Composite Decking

Step One

If you can reach or see underneath the cracked composite board or boards, you should check them. This is to determine the extent of the damage. If the boards are cracked at the top and not at the bottom, you can simply turn them over.

You should unscrew the board from the joists and turn the top to the bottom. After that, you should screw the plastic composite board back into its place. Please note that cracks in the board will compromise its structural integrity, meaning it will not be as strong and be unable to bear the same weight.

This step is not suitable if you will be regularly walking on the board, for example, if it is in the middle of your deck.

Step Two

If you check the bottom of the board and notice that you cannot reverse it, it will need to be repaired or replaced. You should use an air nozzle or compressor to blow or send air into the crack. This will enable you to remove any debris, like twigs, chips, and dust, that hides in the crack. 

Clearing the crack properly will ensure you can assess the extent of the damage. It is important in most cases that, with large cracks, the board will need replacing and that even when aiming to fix a crack, it will not be as strong as a new board. 

Step Three

After removing all the hidden debris from the crack, you can use a cloth you have soaked in mineral spirits to clean the crack. You are preparing the crack for the material that you will use to seal it, so be diligent about it.

Step Four

You need masking tape for this part. Ensure that you get good tape for the best results. Place strips of tape on both sides of the crack on your composite decking board. Ensure that the tape doesn’t cover the crack but is large enough to protect the other part of your decking.

Step Five

You will need a composite filler for this task. It is the composite filler that you will put in the crack on your plastic wood decking board. Use a shaped object to cut the filler’s end at an angle that is convenient for you. Then, you should place the tip on the composite filler tube at one end of the crack. Afterwards, squeeze the content of the composite filler tube into the crack and make it spread evenly.

You can use a knife to push the filler deep into the crack. Then, you should let the composite filler dry in the crack overnight, and you should remove the tape when it is dry.

If you are unsure whether it is safe to repair your composite decking board or unsure how to do so, it is always recommended to consult a professional before doing so.

Safety should always be your number one priority and any board that you will be walking on should be replaced properly. If your cracking was caused by an installation issue, the subframe or boards will have to be re-installed accurately, or the issue will persist.


You can fix your cracked composite decking by turning the board or using composite fillers to cover the crack. Always assess the damage fully prior to attempting to fix it, and consult a professional if you are unsure.

Leave a Reply

Your email address will not be published. Required fields are marked *

Your email address will not be published. Required fields are marked *