Why Do Deck Boards Crack, and How Can You Prevent It?

Outdoor decks are the highlight of many backyards, offering a perfect setting for relaxing, entertaining, and enjoying the outdoors. However, over time, many homeowners notice cracks appearing in their deck boards.

These cracks can detract from the beauty of the deck, create safety hazards, and lead to more significant damage if left untreated. Understanding why deck boards crack and how to prevent these issues is crucial for maintaining the longevity and appearance of your outdoor space.

Causes of Cracking in Deck Boards

1. Moisture Fluctuations

Wood is a hygroscopic material, meaning it absorbs and releases moisture from the environment. Changes in humidity and temperature cause wood to expand and contract, which can lead to cracking over time. This is especially prevalent in areas with significant seasonal changes.

2. Sun Exposure

Direct sunlight can cause the wood to dry out and become brittle, making it more susceptible to cracking. UV rays break down the lignin in wood, which holds the wood fibers together, leading to the deterioration of the deck boards.

3. Improper Installation

Deck boards that are not properly installed can also lead to cracking. This includes boards that are too tightly spaced, not allowing for the natural expansion and contraction of the wood, and boards that are not adequately secured to the deck structure.

4. Lack of Maintenance

Neglecting deck maintenance, such as regular cleaning and sealing, can accelerate the cracking process. Dirt, grime, and moisture can accumulate on the surface and in cracks, further exacerbating the problem.

How to Prevent Cracking in Deck Boards

1. Choose the Right Material

Consider using composite decking materials, which are designed to resist moisture, sun damage, and temperature fluctuations. If you prefer wood, opt for species known for their durability and resistance to cracking, such as Ipe, Cumaru, Teak, Tigerwood, Garapa, Brazilian Redwood and Mahogany.

2. Apply Sealant Regularly

A high-quality sealant can protect softwood deck boards from moisture and UV damage. Apply a sealant at least every two to three years, or more frequently if recommended by the product manufacturer or based on your local climate conditions.

3. Ensure Proper Installation

Make sure deck boards are installed with the correct spacing to allow for expansion and contraction. Use quality fasteners and follow best practices for securing deck boards to the underlying structure.

4. Maintain Regularly

Regular maintenance, including cleaning and inspecting the deck for signs of damage, can prevent small issues from becoming bigger problems. Address any cracks or damage promptly to prevent further deterioration.

5. Use Deck Board Covers

For an additional layer of protection, consider using deck board covers. These products can shield the wood from direct sunlight and moisture, further extending the life of your deck.

6. Minimize Direct Sun Exposure

If possible, design your deck with some shaded areas to reduce the amount of direct sunlight on the wood. Using patio umbrellas, pergolas, or other shading structures can help protect your deck from UV damage.


Cracking in outdoor deck boards is a common issue that results from environmental exposure, improper installation, and lack of maintenance. By understanding the causes of these cracks and implementing preventive measures, you can extend the life of your deck and keep it looking beautiful for years to come. Regular maintenance, choosing the right materials, and proper installation are key to preventing cracking and ensuring your deck remains a safe and enjoyable outdoor living space.

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