Coating Lumber Before Building a Deck: When and How

Many homeowners and DIY enthusiasts wonder whether it is necessary to apply a water seal to lumber before building a deck. This guide aims to clarify the benefits and potential drawbacks of pre-coating lumber, tailored to different types of lumber.

Is There a Reason Not to Coat Lumber Before Building a Deck?

In most cases, there is no compelling reason not to apply a water seal to lumber before building a deck. Applying a sealant prior to construction can enhance the overall longevity and aesthetic appeal of the deck. However, the effectiveness of this step depends on several factors, including the type of lumber and its moisture content.

Factors Influencing When to Apply Sealant

1. Pressure Treated Pine: This type of lumber requires time to dry out completely before applying a sealant. In fact, it is recommended to install pressure treated pine when it is still wet. As the lumber dries, it will naturally twist, warp, and shrink. By installing it in its damp state, you can avoid the need for gaps between boards, as they will naturally form as the wood shrinks over time. However, if the lumber is bone dry, it might be wise to apply the sealant before installation to ensure proper adhesion.

2. Cedar: Cedar is a popular choice for decks due to its natural resistance to decay and pests. If the cedar is bone dry, sealing it before installation is an excellent idea. The sealant will protect the wood from moisture, preserving its natural beauty and extending its lifespan.

3. Tropical Hardwoods: These durable woods can be sealed at any time, allowing for more flexibility in the construction process. However, it is important to ensure that any new lumber, regardless of type, is allowed to dry out naturally before applying sealant or treating it with a stain or weather treatment. Premature application can lead to poor penetration of the sealant into the wood.

Techniques for Proper Lumber Sealing

Sealing lumber after the deck is installed can be less efficient and more time-consuming. Once the deck is built, you would need to stack and unstack the lumber, seal each piece individually, and then reinstall it, which can be labor-intensive. It is generally more practical to apply the sealant to the entire stack of lumber before it is installed, saving time and ensuring a consistent application.

Furthermore, if the lumber is sufficiently dry, applying a sealant or paint prior to installation can significantly extend the life of the deck. However, if the lumber is new, green, and has a higher moisture content, sealing it may be less effective. In such cases, it is better to install the lumber, allow it to season for a year, and then seal or paint it once it is dry. This approach will help prevent issues such as bubbling and uneven paint application.

Conclusion

Coating lumber with a water seal before building a deck can provide numerous benefits, including extended durability and enhanced appearance. However, the timing and method of application depend on the type of lumber and its moisture content. By understanding these factors and following proper techniques, you can ensure that your deck remains an attractive and durable feature in your outdoor space.

Keywords: deck lumber sealing, pressure treated lumber, deck construction