How to Apply Joist Tape

You probably already know that water can cause significant damage to your deck. You’ve seen the splintering and cracking of timber over time and want to prevent this condition in the new deck you’re building.

The excellent news: Add joist tape (also called flashing or bearer tape) during construction, and you can rest more easily. 

While sealants are essential to cover your decking boards, joist tape will help waterproof your timber deck frame, the deck support posts, and the substructure. Using quality joist tape can protect the top of the deck joist, bearers, rim joist, and the edger board from developing rot and timber decay. It will also help seal screw holes and fasteners to help prevent splitting from freeze and thaw. 

Whether you have a two-story or ground-level deck, timber or composite deck boards, joist flashing tape is essential. 

Choosing the Right Tape

The three main choices for deck flashing tape include butyl, rubberized asphalt, and bitumen. What’s the difference, and which should you choose?

Bitumen, which is made from petroleum and asphalt, will dry out over time, reducing its flashing effectiveness. That leaves butyl or acrylic adhesive as better choices, but butyl as the best choice. 

Butyl rubber tape has many advantages over acrylic-based tape: 

• It is stickier
• It endures less stain
• It has less high-temperature oozing
• It can be applied in a wide range of temperatures
• It is more rubbery than acrylic-based tape, allowing it to flow better around the deck screws and deck fasteners, including hidden deck fasteners and Deckwise, to create a tighter seal. 

The net result: butyl tape provides superior weatherproofing for the timber foundation of your deck. Of course, you want a tape that will last as long as your beams and top of joists.

Selecting the Best Tape

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 typically comes with only a 300-day warranty.  

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 five rolls of Trex Protect Bearer tape and one roll of Trex Protect Bearer Tape. For less than a £77 investment, your deck substructure can last as long as the decking it supports.

As with any item you are buying, cost comparisons alone may not be the right approach to selecting the best joist and bearer tape. It would be best to consider the full cost to protect your deck, which involves the price you pay and the quality of the tape you use.

Remember, this is like your insurance policy on your deck substructure, so while you don’t want to bust your budget on joist and bearer tape, you don’t want to skimp on quality to get a slightly lower price.

How to Install Deck Joist Tape

Contractors or DIYers 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.

When applying bearer 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 long-term durability of the tape. A thick tape can be challenging to install. 

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

Installing self-adhering bearer tape is a relatively simple process, with four main steps. To see an overview of these steps, check out this video.

1. Prepare your surface. Trex Protect Tape is applied to horizontal and vertical surfaces such as all joists, bearers, steps, stair stringers, under joist hangars, and other surfaces. It has three widths, 40 mm x 20 m for joists, 100 mm x 20 m for bearers, and 270.4 mm x 15.24 m making it convenient to apply to double joists and bearers. 

When pulling deck boards onto the deck, use a piece of plywood or wafer board to overhang the edge of the deck. This method will prevent the product from rolling up and pulling up from the end of the joists.

2. Remove the backing of the butyl tape while applying the tape directly to the surface. Run your hand over the tape and firmly press it onto the joists.

3. After covering all the joists, rim joists, bearers, stringers, and ledger board, cut the tape to length using a utility knife. 

As you begin deck building, don’t forget the joist tape/deck flashing tape. It’s an easy DIY fix — or easy for your builder to add. Joist tape will provide hidden protection you can count on.