How To Fix Swollen Composite Decking Boards

Henry A
How to
Swollen decking board

One of the possible problems of having a decking is swelling. If you have decking or planning to install one, you may have encountered this problem. The question is, how do you fix swollen composite decking boards? And why do they swell in the first place? And do composite decking boards swell?

Why Do Decking Boards Become Swollen?

Decking boards become swollen because of moisture and temperature. The boards absorb the moisture, causing it to swell. Wooden decking is the most susceptible to swelling. When the expansion of the board is too much, it can warp the board. After swelling, most decking boards will contract after the moisture removes itself from the boards.

Why is this an issue? The movement of the boards can damage the decking. If the decking absorbs too much moisture, the decking boards can warp and bend. The constant contraction and expansion also loosen fasteners over time. Nails are more prone than screws.

Do Composite Decking Boards Swell?

As previously mentioned, wooden decking boards are the most prone to constant expansion and contraction. But how about composite decking boards? Do they become swollen?

Composites or, more accurately, wood plastic composites (WPC) do swell. However, the amount of moisture they absorb compared to wooden decking boards is considerably less. Because of their construction, they are more resistant to swelling. But that doesn’t mean that they don’t expand.

Because composite decking boards do have wooden fibres, these fibres absorb moisture. And because the fibres are mixed with the plastics, the swelling of composites is uniform.

So to summarise, using composite decking is an excellent choice if you’re planning to build decking and you’re concerned about swelling. However, you should remember that not all composites are the same. Some are more resistant than others.

The best composites will absorb only about 5% of moisture, even when submerged in water for a month. Others may absorb twice or thrice that amount. For best results, you may want to use capped composite decking boards for extra protection.

How to Fix Swollen Boards

How to fix swollen decking board

The only way to fix swollen wood or composite boards is by air-drying them. Moisture will leave the boards and will return to their original size. However, there is not much you can do if the wooden decking boards are warped beyond repair.

The best thing to do is to replace it with new boards. As for composites, some of them are resistant to warping and bending. They will return to their original size eventually. You may also need to re-attach some nails or screws that became loose due to the movement of the boards.

Swelling is a huge problem for decking owners. As mentioned, there is very little you can do to fix boards that are too affected by the swelling. If that’s the case, the only way to fix it is to remove the boards and replace them with new ones. However, there are many ways to prevent this problem from occurring. Doing so will save you time and materials.

For wood, you will need to purchase a sealant. It is applied to wood to prevent moisture from entering the boards. You will need to re-apply sealants every few years since they do come off over time. However, if you are using composite decking boards to build decking, you don’t need to do anything to the boards. As previously mentioned, while they swell, they are resistant to warping, especially capped composites.

During the installation, there are also things that you can do to minimise the damage done by swelling. For both composites and wood, you would need to air-dry them first so that they’ll return to their original size before you install them.

You will also need to consider proper decking spacing. If you install the boards too close to each other, the boards may swell and create friction. The boards can lift away from the subframe, making the decking uneven underfoot, which will lead to accidents. The amount of space you’ll need will depend on the materials that you’ll be using. To know the exact details on board spacing, you can refer to the manufacturer’s installation guides or talk to them directly for help and advice on the spacing of their composite decking boards.

Also, check out which is cheaper between deck and paver. 


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