A deck is a nice addition to your outdoor living space. Whether you are building a pool as well or you are simply looking for a place that you can entertain people outside, a deck is a great place. One of the most common questions that people ask when they are putting a deck is whether the deck boards are will shrink or expand.

The funny thing about deck boards is that they are going to do both. Fibers can hold in moisture. So when the weather is humid outside, these fibers are going to collect this moisture, making the fibers expand. And since the fibers are expanding, so are the boards. When the season is dryer, they are going to lose moisture so that they shrink.

Deck Boards & Shrinkage

The majority of boards used for decks will be pressure treated. This means that they are going to be a bit wet when they are new. When they’re wet, the board’s fibers are going to hold the moisture and expand. Since the boards are generally installed outside, as time goes by sun exposure is going to dry the boards and make them shrink slightly.

However, it won’t end there. because of humidity fluctuate, the boards are going to keep on cycling between shrinking and expansion.

What Causes Deck Boards to Shrink

There are a lot of factors which are going to determine whether deck boards are going to expand or shrink. The reason is that wood’s made of fibers, and the fibers can hold moisture.

So, as mentioned before, when the fibers have moisture in them, they are going to grow bigger an expand. When the fibers become dry, those fibers contract. This makes the boards shrink.

This is even more complicated because the boards are put outdoors and they’re subject to changing seasons, temperatures and humidity levels. During the more humid months, the fibers are going to have a lot of moisture. This means that they are going to expand. When the weather is dryer, they then will contract as the moisture is lost.

Installing During Dryer Months

If the boards are being installed when it’s drier, you want to think about that they are going to soak moisture in when the weather is more humid. So you want to think about leaving a gap that’s big enough between your boars. A good gap is anywhere between ¼ – 1/8 of an inch.

  • ¼” gaps offer drainage, debris removal and ventilation. But they can also be more dangerous and cause tripping.
  • 1/8” gaps are less hazardous.
  • A 1/4 inch gap is more desirable with respect to other factors such as ventilation, drainage, and debris removal.

Installing During Humid Months

If you are installing boards while its humid, this process is often more complicated. Even though you might think it’s going to be easierbut you’ll have to consider the expansion during humidity season and how they are going to shrink during drier months.

  • Untreated dry months – leave a gap of around ¼”. This will let them expand and shrink with the right gap.
  • Pressure treated – Leave a gap of around 1/8”. With this, your boards are going to go flush throughout the humid season. Then they’ll contract when it’s dryer.

Worried about doing it yourself? Let us do it for you. Contact us today to get a quote.