Is Deck Joist Tape Necessary?

When building or renovating a deck, one often overlooked but essential component is deck joist tape. This simple, affordable product can significantly extend the lifespan of your deck frame, especially considering the changes in pressure-treated lumber over the years.

The Evolution of Pressure-Treated Lumber

In the past, pressure-treated lumber contained arsenic, which made it highly resistant to rot and pests. However, due to health and environmental concerns, the industry shifted to using other chemicals, such as alkaline copper quaternary (ACQ) and copper azole (CA).

While these newer treatments are safer, they are showing signs they may not be as effective in preventing decay, leading to a noticeable decrease in the lifespan of pressure-treated lumber.

Many homeowners who built decks with the newer pressure-treated wood have experienced significant frame rot in as little as 10 years. This premature rotting is a substantial issue, especially given the investment and effort put into deck construction.

The Vulnerability of Deck Joists

The top of the deck joists is one of the most common area where rot can begin. This happens because water gets trapped on top of the joist and under the deck boards, creating a moist environment that doesn’t see sunlight and has limited airflow. Over time, this trapped moisture leads to wood decay, compromising the integrity of the entire deck structure.

The Role of Deck Joist Tape

Deck joist tape is a waterproofing barrier that adheres to the top of deck joists, protecting them from moisture. By applying this tape, you can significantly reduce the chances of water infiltration, thus preventing rot and extending the life of your deck frame.

If you’re constructing a deck using longer-lasting materials such as PVC decking, composite decking, or hardwood decking, the importance of deck joist tape becomes even more critical. These materials are designed to outlast traditional softwood decking, sometimes by decades. However, if your deck frame fails due to rot, the longevity of the decking material becomes irrelevant.

By keeping the tops of your deck joists dry, you ensure that your entire deck structure can last as long as the premium materials you’ve chosen for your decking surface.

Steel Deck Framing

Steel deck frames are the ultimate long lasting deck frame solution. Steel deck frames are warrantied for 25 years against any corrosion that would make your steel deck frame become structurally unfit. This means your steel deck frame will last well beyond the 25 year mark.

Steel Deck Framing
New Castle Steel Deck Framing – Made in USA

Steel deck frames offer many other advantages as well:

  • Steel deck joists can be moved by one person.
  • Stays flat and level, opposed to pressure treated joists usually need to be flattened and can twist and sag over time.
  • Can span further distances.
  • Non-combustible material has a Class 1A fire rating and is rot- and termite-proof.
  • More aesthetically pleasing than green pressure treated lumber.


In conclusion, deck joist tape is a necessary investment for anyone looking to build a durable and long-lasting deck. With the newer pressure-treated lumber not lasting as long as its predecessors, and the susceptibility of deck joists to water damage, taking preventative measures is crucial. Applying deck joist tape is a simple and cost-effective way to protect your deck frame from rot, ensuring that your deck remains safe and functional for many years to come. If you’re building with PVC, composite, or hardwood decking and can’t afford a steel frame, deck joist tape isn’t just recommended—it’s essential.

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