Construction Tape

Is Deck Joist Sealing Tape Important? What You Need To Know

While today’s high-performing deck boards can even last for up to 20 years, but nothing is guaranteed about the substructure that supports the deck. Moreover, if the bearers and posts are made of timber, they would likely deteriorate after some time.

Experts have found out that timber foundations tend to show signs of decay or rotting after 7 or 8 years. So, the solution lies in deck joist sealing tape that shields the bearers and joists effectively from the moisture that leads to rotting.

Hence, having protective tape when building a timber substructure is a necessity. In this post, you get to know why it is important to use sealing tape for deck joist and other aspects of it.


Deck joist flashing or sealing tape is a kind of water-resistant butyl adhesive that is used to keep moisture from entering the mainframe of your deck. While you may get high-quality composite deck boards that are both moisture and water-resistant, the lumber used for the ledger and joists is vulnerable to water damage.

Hence, the best way to protect the substructure is to use sealing tape for the joists. Keep in mind that a healthy substructure is very important for the overall health and appearance of your deck. Moreover, it benefits you in the following ways as well.

  • Increases the life expectancy of your deck
  • Saves you from future replacement or maintenance costs
  • Improves the structural integrity of your deck
  • You remain worry-free and enjoy your deck year after year


Whenever you are adding a deck, you are not just adding outdoor living space. In reality, you are making another big investment. For example, if you are having a 400 square foot deck, the cost could be anywhere between $11000 and $17500 for a wooden deck and between $12000 and $24500 for a composite deck.

With all that going into building a nice deck, making use of deck joist flashing tape might appear to be a step that almost everyone skips. Also, taping your deck joists is no requirement that everyone follows as an important building code. So, you may ask yourself, “How will it matter if I skip this step?”

Ignoring this crucial step can make a great difference in the future. Whenever it rains, debris and water are trapped in the crannies and nooks between the deck boards and joists. As a result, it creates a moist atmosphere, which becomes very difficult to dry.

Moreover, the trapped moisture breaks down the wood joists over time and causes them to decay and rot. Deck joist flashing tape builds a waterproof barrier that protects the joists from getting damaged because of the moisture. Even if your deck joists have treated wood, it will rot eventually.

Hence, skipping joist sealing tape might not impact you in the short term, it can make a lot of difference in the long run. Apart from that, water can create enough damage to the metal hangers that hold the deck board frame together. If left unprotected, the joist hangers that hold the deck corrode because of the copper leaching out of the treated wood.

Therefore, if you want the full support of your deck’s substructure and increase its life, you can protect that for a little extra cost. Joist sealing tape protects the deck substructure affordably.


The deck joist flashing tape should be applied on top of the joists like a cap. And, proper care is should be taken to make sure not to wrap the entire timber. That way, the timber won’t be stuffed and can breathe with ease. The tape creates a strong seal and guards against moisture.

As such, this will prevent the water sitting on top to flow underneath the surface and eat away the timber after some time. Moreover, the tape should be used around the timber that has significant contact with the ground. Also, you can use it on fence posts to create a watertight and waterproof seal.

In addition, the cut ends on the timber are the weakest spot where moisture accumulates and cause damage with ease. However, a single layer of sealing tape can resolve this issue with ease. Another important area where you may need to apply the sealing tape is the fasteners.

A small layer of the sealing tape helps to prevent corrosion around the treated wood and stainless steel fittings. Moreover, deck sealing tape comes in a variety of widths to make sure that it covers timbers of variable sizes.


The benefits of using sealing tape for deck joists are many. It features water, smoke, and air-tight along with an easy release system. Moreover, it is self-sealing and UV stable. The sealing tape that’s created from a robust polymer acrylic adhesive gives you the ultimate weatherproof and waterproof seal.

For how long the seal will last depends on the manufacturer. However, some brands provide you with a permanent adhesive bond that might last for up to 50 years. And, comes with a 25-year warranty as well. Now, this is the kind of benefit that you may want for your beautiful deck.

Furthermore, it is very important to use deck joist sealing tape for composite deck boards because the chances of absorbing moisture on the timber substructure increases because the water drains off the deck boards that have water-resistant abilities.

So, when you leave the timber substructure unattended for a long time, the amounts of moisture increase over time and the frame begins to rot. Another greatest benefit of using deck joist flashing tapes is that they remain stable between temperatures -40C and +93C. They don’t peel, crack, or lose strength.


As you go through the benefits of using sealing tape on deck joists, the answer to the question is very clear. Is deck joist sealing tape important? Yes, it is. So, whether you are choosing a traditional hardwood or modern decking area, don’t forget about these sealing tapes.