how much do deck boards shrink

Full Answer

Do deck boards shrink or expand?

Deck boards can both shrink and expand. This is why it is necessary to leave appropriate spacing between them when building a deck. Most deck boards are pressure treated, which means they will be somewhat wet when they’re new. When wet, the fiber in the woods holds moisture and, as a result, expands.

How much does wood shrink when it dries?

Wood doesn’t expand or contract equally in all directions. For example, a 16-ft pine board could potentially shrink around 1/8 to 3/16” in length, and ¼" in width as it dries. Different wood species have different coefficients of shrinkage as they dry. The importance of deck board spacing can’t be overemphasized.

Why does decking shrink when it rains?

As a result, the fibers in a deck board will hold moisture and expand during the humid season, leading the board as a whole to expand a little. And this when moisture is lost during the dryer seasons, the fibers will shrink and so with the boards.

How much gap should be between deck boards?

For kiln-dried wood with a relatively low moisture content of around 10 to 12% and a relative humidity level of about 35 to 45%, the final deck gap should be about 1/4 inch.

Do deck boards shrink in length?

Deck boards will shrink, and not only that, they will even expand. Fibers have the ability to hold moisture in them. So when the outside environment is humid, the fibers collect moisture and expand, leading the boards to expand. In the dryer seasons, they lose moisture and shrink as a result.

How long does it take for pressure treated wood to shrink?

Over time, most treated lumber will shrink slightly across its width as it dries out. Take this small amount of shrinkage into account when laying decking or fence boards. After being outdoors for six to 12 months, treated lumber will develop cracks, called "checks," along the surface of each board.

Will wet deck boards shrink?

If you have a high moisture content, leave less space between the boards as they will shrink as the moisture is released. If you have a low moisture content, leave more space to accommodate the expansion of the boards as they gain more moisture.

Does pressure treated decking shrink?

Even products that are sealed and treated are going to shrink. This most typically occurs across the width of boards, so builders should take into consideration the fact that their lumber will shrink over time. Additionally, as part of the drying stage of treated wood, the boards will crack, also referred to as checks.

Do deck boards shrink in width?

Air-dried decking can often be installed with a gap less than 1/4 inch (6.5 mm) because the boards will likely end up shrinking in width rather than expanding.

Does wood ever stop shrinking?

A: No. The amount of shrinkage varies from species to species, but generally wood shrinks 8 to 10 percent tangentially, 4 to 5 percent radially, and close to zero percent lengthwise.

How much does a board shrink when it dries?

Tangential shrinkage can vary from about 3% up to around 12%; most woods fall in the range of about 6% to 10% tangential shrinkage. (Accordingly, volumetric shrinkage is typically within the range of 9% to 15% for most wood species.)

How do I keep my deck from shrinking?

Just like warping, bowing occurs when moisture leaves the boards causing the wood to shrink. By adding moisture back into the wood, you can correct the warping with a little bit of pressure. Add water to the board until it starts to pool. Leave it sitting on the surface for roughly 15 minutes before wiping it away.

Should there be a gap between decking and house?

When building a deck, it is highly recommended to establish a gap between 1/8 and 1/4 of an inch between the deck and the wall of the house.

Does decking shrink in the heat?

When decking is exposed to hot conditions it can shrink and dry out. When wood is dried out it is more likely to retain water, which can cause the wood to swell and lead to rot. In addition, the cycle of swelling and drying from water and heat can cause wood to crack, split and warp.

Should you space pressure treated deck boards?

Leave Gap: If the pressure treated wood has been kiln dried after treatment (KDAT), leave a 1/8” gap (the thickness of an 8-penny nail) between the boards when attaching, since the wood will expand slightly over time.

Is it better to use longer or shorter deck boards?

In general, you always want to use long boards if you're able. The more boards you use, the more weak points you're creating where they join and the greater the chance of damage to your deck. You'll see less warping and twisting, which in turn means your deck will last a lot longer.

Will wet wood shrink when it dries?

Wood shrinks or swells as its moisture content changes, but only when water is taken up or given off from the cell walls. Any change in water content in the cell cavity will have no effect on the dimension of the wood.

How much will fresh cut lumber shrink?

As a result, the expected shrinkage in the width of a board is usually some percentage between those given for radial and tangential shrinkage. The longitudinal shrinkage of wood is generally 0.1 to 0.2 percent of the green dimension and is considered insignificant.

Does timber shrink more in length or width?

Wood expands and contracts mostly across its width. Measure Width in inches. Step 2: Find the average yearly change in moisture content. Wet air expands wood, dry air shrinks it.

How do you know when pressure treated wood is ready?

Pressure treated wood needs time to dry out before it's primed or painted. You can expect 3-4 months before the moisture levels fully go down. If moisture beads up on the surface, it's still too damp. You'll know the treated wood is ready to paint when it absorbs water instead of repelling it.

What is the purpose of spacing between deck boards?

Spacing between deck boards provide a few critical functions. The primary function is to drain water from the deck. Gaps that are narrow (1/8”), can catch debris, specifically on top of the joists, and can be difficult to clean out. Larger gaps, such as 1/4”, allow more of this material to fall through the deck.

What is man made decking made of?

There are over a hundred different man-made decking products on the market today. Most are composed of wood-plastic composite, capped composite, vinyl and aluminum. They offer low-maintenance and a variety of appearances. If playback doesn't begin shortly, try restarting your device.

Why is decking important?

Your choice in decking is very important because it is the surface you will see, walk on, maintain and have to live with for years to come. Do some research on our site to find a material that lends itself to your tastes.

What kind of wood is used for decking?

People used redwood, cedar, pressure-treated pine and even some exotic hardwoods. Wood has some beautiful natural characteristics, but also requires some maintenance. Decking comes in many forms these days. There are over a hundred different man-made decking products on the market today.

Is ventilation necessary for a deck?

Ventilation below the deck is also enhanced by the gaps between the deck boards, but this is only important in ground-level decks. For lumber decking, both the moisture content of the lumber and the environment its installed in matter.

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Why Is Deck Spacing Necessary?

The most important reason to have a spacing gap is to allow the boards the room to expand and contract naturally.

How to determine spacing for wood boards?

The best way to decide the appropriate spacing for your boards is to check the moisture content of the wood before installation. The amount of moisture in the wood will let you know whether the wood will expand or shrink right away. As the humidity increases, the moisture content increases which causes the wood to expand.

What is deck spacing?

Spacing on a deck refers to the small edge-to-edge gap between decking boards, not the ends of the boards. While this gap is fairly small, it is still a crucial component to any good deck. Without the right deck spacing, the boards may expand, cup, and buckle out of place. As a result, you may have to replace broken decking, ...

Why is it important to maximize air flow underneath and around deck boards?

In order to minimize cupping and expansion / contraction of the boards throughout the seasons , it is important to maximize air-flow underneath and around the deck boards.

What is the gap between deck boards?

Leaving a gap between boards is critical for a well-built deck that will have space to drain, dry, expand and contract without causing the wood any damage. But, you also want to be sure you leave the right size gap: Go too small, and there won’t be enough space; go too big, and the gap can become a safety hazard.

Why spacing deck boards?

Makes for Easier Cleaning. Another benefit to proper deck board spacing is that the spaces help make it easier to sweep away debris from the surface of the decking. While debris may not seem like a big deal, it will take away from the aesthetic of your deck.

What is the moisture content of exterior wood?

Typical moisture contents for exterior wood products are between 10% and 14%, depending on the local climate and humidity - anything above 15% is considered high moisture content and thse boards will likely continue to shrink.

Why is it important to space cedar deck boards?

It is important to space cedar deck boards even if the amount by that the wood expands is minuscule. Mainly because you want some space between the boards for water to run through and to give the boards some space to breathe. Both is important to ensure the longevity of your deck.

How much does cedar shrink?

Cedar wood shrinks on average about 1/8 inches and it can expand about as much.

What is the most popular deck in the US?

Cedar decks are probably the most popular decks used throughout the US. Building your own cedar deck isn´t as hard as you might think considering you keep some very important things in mind.

How much space between cedar boards?

Both is important to ensure the longevity of your deck. So to ensure the longevity of your cedar deck I would highly recommend leaving at least 1/8 inch space between the boards. This will ensure that any water or snow can easily run through the spaces and does not sit on top of the board for too long.

Can cedar deck boards expand?

First of all, cedar deck boards can shrink and expand depending on how high or low the humidity levels outside are. If it is especially dry outside then cedar wood will contract and shrink and if it is quite wet outside or it the humidity levels are high then cedar deck boards will expand. Video Player is loading.

Does cedar shrink or expand?

Cedar is known for eating certain types of screws. And the other big thing to keep in mind is that cedar tends to move quite a lot. So you have to take into account that cedar can indeed shrink and expand quite a lot.

Does cedar wood rot?

Even though cedar wood is quite resistant to rot it is not completely immune to it meaning it will rot eventually. And if you don´t leave enough space between the boards then water residue may speed up the rotting process quite drastically.