What is Joist Tape?

Prevent Deck Rot

While composite deck boards have grown tremendously popular in recent years, the deck’s supporting structure is most often still made of timber. Because timber is economical and readily available, it is a popular choice for framing new deck construction.

The challenge: Water damage could be your new timber deck’s greatest enemy. How do we go about waterproofing? What building materials or building products can make the most significant difference for a small price?

The answer: Joist tape, also known as joist protection tape.

Water leaking through your deck boards can cause hidden damage unless your bearers and joists are protected.

Using a quality deck joist tape can protect the top of the joist, rim joist, and ledger board from developing rot and timber decay. A butyl-based tape blocks moisture and helps decking screws hold longer and stronger than acrylic or asphalt-based tape. Other benefits of joist tape: it can act as a barrier between timber and galvanized metal such as joist hangers, help seal deck fasteners, prevent moisture penetration, eliminate splitting from freeze and thaw and provide a non-skid surface, making it safer during installation.

Learn more about how choosing the right joist tape during construction can add years of life to your deck.

How to Choose Joist Tape

There are several factors in choosing joist tape. Be sure to consider the following:

Which Material?

Joist tape typically comes in three types: acrylic tape (G Tape), butyl, and bitumen. Bitumen, made from petroleum and asphalt, will dry out over time, reducing the flashing effectiveness. That leaves butyl or acrylic. Butyl rubber tape has many advantages over an acrylic-based tape. Butyl tape, such as Trex Protect, is stickier, endures less stain, has less high-temperature oozing, and can be applied in a wide range of temperatures. Butyl tape is also more rubbery than acrylic-based tape, allowing it to flow better around the screws holes to create a tighter seal.

Easy Install

Any contractor or DIY homeowner will tell you to buy a butyl tape that is easy to install and requires little trimming.  A self-adhesive butyl tape that lies directly on the boards requires minimum cuts with little overlap.

Thick or Thin?

When applying joist tape to your bearers and joists, you want to be sure to purchase a tape that is not too thin and not too thick.  With thin tape, you risk the long-term durability of the tape.  A thick tape can be difficult to install. You want a tape that will last as long as your bearers and joists. Trex Protect is available in two widths: 40 mm x 20 m for joists and 100 mm x 20 m for bearers.

Long-Lasting Results

Trex Protect is guaranteed to withstand the test of time. It comes with a 25-year warranty, so it lasts as long as the decking it supports. Acrylic tape comes with only a 300-day warranty.

Joist Tape for Decks

The average deck begins to experience water damage within 8 to 10 years. High-performance Trex Protect fights the rot and guards against costly future water damage — at a low cost. Protecting an average-size deck measuring 3.5m x 7.5m will require approximately 5 rolls of Trex Protect Joist Tape and one roll of Trex Protect Bearer Tape. For less than a $120 investment, your deck substructure can last as long as the decking it supports.

To find out exactly how much Trex Protect Joist and Bearer Tape your project requires, use our Materials Estimator.

Easy-to-install, self-adhesive Trex RainEscape Wall Flash seals the space between your house and ledger board to keep water out. Wall flash is best used during the construction of a new deck and is another small investment with big returns.

Trex RainEscape® Wall Flash comes with a 25-year warranty from Trex, the world’s #1 composite decking brand. See how Trex RainEscape® Wall Flash protects in this video.

How to Install Joist Tape

Installing joist tape has just a few straightforward steps, detailed in this video. You can also find a summary of the instructions below:

1. Prepare. Clean the surface, ensuring it is clean and free from debris. 
2. Remove the butyl tape backing while applying directly to the surface. Run your hand over the tape and firmly press it onto the joists and bearers.
3. Apply Trex Protect to all the joists, rim joists, bearers, stringers, support posts, and the ledger board. After covering all horizontal and vertical surfaces, cut the tape to length with a utility knife.

It can also act as a barrier between the timber and galvanized metal, such as joist hangers. 

As you begin deck building, don’t forget the joist tape. It’s like your secret deck protector. Don’t let timber rot become the enemy of your beautiful outdoor living experience.