So, you’ve made it through the hard part of deck building: installing the footings and constructing the framework. To make sure your deck stands for many years as a testament to your carpentry skills, you need the best deck joist tape you can buy to protect those vulnerable joists.
Deck joist tape is a self-adhering tape used as flashing on deck joists and ledger boards. This tape, which is applied cold, protects your joists from water damage by creating a water barrier between treated lumber and non-corrosive galvanized metal hangers.
I’ve put together a guide of the best deck tapes on the market to help you decide what will work best for your masterpiece. In this article, we’ll go over what factors you should consider when shopping for deck joist tape, some basic installation instructions, and even some joist tape alternatives.
- Why do You Need Joist Tape?
- Best Deck Joist Tape – Our Top Recommendations
- What to Consider Before Buying a Deck Joist Tape
- How to Install Joist Tape
- Joist Tape Alternative
Why do You Need Joist Tape?
With all that goes into building decks, applying joist tape may seem like one step you can skip. Not everyone uses deck tape when constructing a deck. And, since taping your joists is typically not a building code requirement, you might be asking yourself, “What difference will it make if I skip this step?” It could make quite a big difference.
When it rains, water and debris can become trapped in the nooks and crannies between the joists and deck boards, creating a moist environment that is slow to dry. Over time this trapped moisture will break down the wood joists, eventually causing them to rot. Deck joist tape creates a waterproof barrier that protects the joists.
And yes, even treated wood will eventually rot if not allowed to dry. So, while skipping joist tape may not matter much in the short term, it could make a world of difference in the long term.
In addition to the wood parts of your deck, water can also wreak havoc on the metal hangers that hold your deck framing together. Left unprotected, the copper in the treated wood will leach out of the wood, corroding the joist hangers holding your deck together.
Placing a waterproof membrane between the metal hangers and the treated wood prevents this chemical reaction from taking place. Now, before you point out that this wasn’t an issue with your old deck, keep in mind that this is a relatively new problem.
Before 2004, chromated copper arsenate (CCA) was used to create treated lumber. Although the presence of arsenic in CCA created a health hazard, this wood preservative did not cause major problems for metal fasteners and connectors.
After arsenic was banned from this process, the lumber industry began using other preservatives, including alkaline copper quaternary (ACQ) and copper azole (CA-B and CA-C).
Because these new preservatives contain much higher concentrations of copper, they wreak havoc on the zinc in galvanized fasteners. Still not convinced? In 2008, Simpson Strong Tie, the biggest manufacturer of metal hangers, published a bulletin stating that CA-B and ACQ are roughly twice as corrosive as CCA.
You need to protect your metal hangers. This is where deck joist tape comes in. Deck joist tape prevents this chemical reaction from happening by creating a barrier between the metal hangers and treated lumber.
Like it or not, you’re going to need to protect your deck framing. But don’t fret. There are many deck joist tape options that can be installed quickly and inexpensively.
Best Deck Joist Tape – Our Top Recommendations
You may find this hard to believe, but not all deck joist tapes are created equal. Some are easy to install while others take more time but offer maximum protection. In this section, we’ll go over the pros and cons of the top deck joist tapes on the market.
1. Imus Seal Butyl Joist TapeThe company Styxe is serious about protecting your deck joists. It’s the only product they make. That should give you some idea as to how good their self-adhering flashing tape for joists is. Unlike other tapes that stick (pun intended) with tried and true tar paper material, Imus goes with butyl rubber.
Why? Rubber has a few advantages over the tar paper. As anyone who has some roofing experience under their belt knows, tar paper is prone to tearing. Try tearing a rubber inner tube. Exactly. Butyl tape is much more durable.
Rubber also has a nice quality of closing in around holes. Thus, when you’re done screwing or nailing through the tape to attach the decking, the rubber closes tightly around the fastener, shielding the hole from damaging water infiltration.
During installation, you need your deck joist tape to stay put. The folks at Styxe know this, which is why they’ve made their tape so sticky. In fact, it’s downright gooey. Just keep in mind that you’re making a commitment when installing this tape. Once it’s down, it’s not coming back up again.
Imus Seal Butyl joist tape, unlike other tapes on this list, also comes in a variety of sizes to handle standard joists, double joists, and ledger boards. Available widths include 1 5/8”, 4” and 6”. All rolls come in 50’ lengths.
- Cheaper than other butyl tapes
- Closes and protects fastener holes
- Very sticky
- Comes in a variety of sizes
- Gooey adhesive can be hard to work with
- Not as thick as other butyl tapes
2. Grace Vycor Deck Protector Self Adhered FlashingLike other deck joist tapes, Grace Vycor’s deck joist tape will protect your joists from water infiltration by creating a waterproof membrane between your decking and frame. Grace Vycor also focuses on the problem that occurs between the metal parts of your deck framing and the wood.
With its wide 4” width and thicker material, Vycor Deck Protector touts its ability to create a waterproof barrier between those metal parts and the wood, preventing your hangers from succumbing to the high copper concentrations in your deck’s treated wood.
And while other deck tapes can also accomplish this task, Vycor is the only tape with an official seal of approval from metal connector giant Simpson Strong-Tie. This makes Vycor a great deck joist protector option.
That said, because it focuses on protecting the joints of your deck, it isn’t optimized for use over joists. It comes in 4” rolls, meaning much of the tape used to protect the length of the joists will have significant overlap and, hence, a significant amount of waste.
And because this tape isn’t as sticky as other tapes on this list, you may have to staple it to the sides to keep all that overlap from peeling up.
Aesthetics can also be an issue. Depending on how visible your deck joists are, you may not like the fact that the Vycor logo and product name are printed all over the tape.
- Protects deck hangers and connectors from corrosion
- Simpson Strong
- Proven name
- Wider tape not optimal for joist widths
- Not as sticky as other tapes
3. Cofair DFB375 Deck Flash BarrierIf you haven’t heard of Cofair before, you should know that this company specializes in manufacturing a variety of protective deck tapes for a whole host of applications, ranging from roofs to mobile homes to gutters and even driveways. Deck Flash Barrier deck tape uses an asphalt adhesive to provide a waterproof membrane between joists and decking. Like other butyl tapes, it is also usable as a buffer between metal and treated wood, preventing the metal corrosion that takes place when the chemicals used to treat the wood and the galvanized metal come into contact.
Deck Flash Barrier also offers some versatility by offering other applications. The company says it will also protect your posts from rotting at the ground level. Simply wrap the posts near the finished grade.
This tape is cheaper than others on this list, but it doesn’t have the same elasticity. As a result, it has a greater tendency to pucker in sunlight. So, be prepared to get your decking installed quickly once the tape has been laid. You’ll also want to use a roller to get maximum adhesion to prevent this from happening.
Also, keep in mind that the 3” wide roll is a little less efficient than narrower rolls. You’ll either have to cut it to get to the 1.5” width of a joist or accept the fact that you’ll have a significant amount of overlap.
- Adhesive fills nails and screw holes
- Cheaper than other tapes
- Sticky Adhesive
- Can be used to protect metal connectors
- Susceptible to puckering in sunlight and heat
- 3” wide width might be overkill
4. DeckWise WiseWrap JoistTapeYou may have heard of DeckWise. This company makes a variety of deck-related products, including hidden deck fasteners, wood care products, and connectors. DeckWise uses polypropylene, a type of malleable plastic, in its WiseWrap JoistTape.
As with other butyl tapes, WiseWrap will protect your joists and provide a barrier between treated wood and metal parts.
This product is designed to stay put. DeckWise describes the adhesive on its deck joist tape as “Super Grip.” And like other flexible tapes on this list, the rubber asphalt adhesive is very sticky.
You won’t have to worry about it coming loose. That said, at 3” this tape is wider than a standard joist, which is 1.5” wide. While this works great for double joists, you’ll have overlap for regular joists.
And, even though this tape is sticky, it does not do a good job of holding to the sides of the joists. You’ll want to use a hand roller to make sure the tape stays in place.
Deckwise WiseWrap is more concerned with aesthetics than it is with using your deck to advertise its product. While other deckwraps are covered in the company logo, Deckwise’s wrap is a matte black, meaning you won’t find yourself reading letters or noticing bright colors through the gaps between your deck boards.
- Sticky adhesive
- Plain black color
- Super Grip adhesive
- Wider tape means more waste
- Doesn’t stick well to sides of boards
5. Trex Protect Joist Butyl TapeOne of the more popular joist tapes you can buy, Trex Protect Joist Butyl Tape is put out by the company that makes the popular engineered decking it’s known for. It makes sense that Trex would manufacture joist tape.
If you’re going to spring for the ultra-durable Trex decking, you’d better have a frame in place that will support it for a long, long time.
Unsurprisingly, this tape works well with the Trex products, including its hidden fastener system. But it also works just as well with standard decking. The adhesive on Trex Protect is very, very sticky. So, unlike other tapes on this list, Trex does a good job of staying put without peeling away from the sides of the joists and just prepared with gloves when applying to avoid sticking the tape to yourself.
At 3 1/8” this tape is thicker than a standard joist, so keep in mind that it is designed to fold over the top of the joist onto the sides. For double joists, this tape will provide a perfect fit over the top.
Trex Protect also matte black, meaning you don’t need to worry about it showing through the gaps in your deck.
And, like other tapes on this list, Trex Protect also will provide a water barrier between treated lumber and galvanized connectors.
This tape comes highly rated, but plan on paying for that Trex name. This tape is more expensive than other joist tape options out there.
- High Quality
- Sticky adhesive Keeps tape in place
- Trex name
- Matte black color
- Sticky adhesive can make installation trickier
6. Pylex 12090 Frame Waterproof StripsWant protection for your joists, but don’t want to pay a lot for it? Go with the old school method of using tar paper. That’s what you get with Pylex 12090 Waterproof strips.
Made from tarred roof paper, this roll of tape offers simple protection for your joists. Installation is easy and fast. There is no sticky adhesive to worry about and no backing to peel off. Simply lay the tape across the tops of the joists and use a staple gun to fasten it.
And, perhaps best of all, it’s cheap. A roll of Pylex tape costs a fraction of the more expensive butyl tapes. That said, it does have some drawbacks. Tar paper is less durable. It is much more likely to tear than butyl tapes. It also does not offer the same protection rubber offers for fasteners. It will not seal the holes created by deck screws or nails.
It also isn’t a great option for creating a waterproof barrier between metal connectors and the joists. Still, you’re looking for a quick and cheap option, these waterproof strips are a good option.
- Quick installation
- Tried and true solution
- Not as durable
- Will not seal fastener holes
7. TimberTech PRO-Tac Flashing and Joist TapeTimberTech is best known for its line of high-end composite decking. So, it’s no wonder that this company turns out what might be best described as heavy-duty joist tape. If you’re going to spend that much money on your decking, you’re going to want the best to preserve the frame that’s holding it up. PRO-Tac Flashing and Joist Tape is the cream of the crop when it comes to joist tape.
It’s designed with a butyl adhesive for maximum stickiness. It’s also one of the thicker tapes you can buy. It’s heavy-duty enough that it won’t get torn off the joists as you’re installing the decking. This tape also provides a very tight seal around fasteners, ensuring that your joists are protected from rot inside and out.
And, unlike other tapes on this list, you don’t need to worry about the temperature when you’re installing it. This tape is rated for use in temperatures ranging from -70 F to 200 F.
PRO-Tac’s size is also optimal. The tape is just over 1.5” wide, making it a perfect fit for standard joists. The tape also comes in a double-sized width for double joists.
This industrial-strength tape, like TimberTech decking products, isn’t cheap. It’s twice as expensive as other butyl tapes on this list.
- High Quality
- Very durable
- Can be installed in all weather
- Thicker tape can be harder to work with
What to Consider Before Buying a Deck Joist Tape
There are a few factors you need to consider when shopping for the right deck tape.
Generally, you’re looking at two options here: butyl, which is a type of rubber, and tar paper, which is very similar to the underlayment you use for roofing your home. Butyl has the advantage of being more pliable and durable.
It won’t tear like tar paper. Butyl tapes also typically have a very strong adhesive that keeps them in place and forms a tight seal around fastener holes, providing additional protection.
Tar paper tapes, in comparison, will not provide a sealant for fastener holes. That said, butyl tapes are significantly more expensive than tar paper.
Installation varies depending on which material you use. Butyl tapes typically have a very sticky adhesive side. Simply peel off the backing and stick the tape to the joists.
Depending on the quality of the product you use, you may need to use a roller to make sure the tape doesn’t pull away from the joist. Tar paper tapes are typically installed by affixing the tape to the joist using a staple gun.
Thicknesses vary with deck joist tape, ranging from 20 mil up to 40 mil. Butyl tapes are typically thicker than tar paper tapes. Generally speaking, the thicker the tape, the stronger and more durable. Do keep in mind that thicker tape can be harder to work with when installing and when laying deck boards.
Widths vary from tape to tape. As a standard joist is 1.5” wide, many tapes are designed to fit this width. Most will be wider than 1.5” to allow for an overlap that creates a cap over the top of the joist.
Some tapes are 3” wide or more to handle double joist parts of your deck. Protecting these areas is critical as water can infiltrate the seam between double-up joists, leading to rot. Some manufacturers sell tapes designed for both widths while others do not.
Deck joist tape typically comes in rolls of 50’ to 75’. You’ll need to calculate the total length of the joists in your framing to determine how many rolls it will take to cover your deck.
Price ranges significantly with deck joist tapes. In general, butyl tapes are much more expensive than tar paper tapes. Of those butyl tapes, the thicker, more heavy-duty tapes, such as TimberTech’s Pro-Tec flashing, are the most expensive tapes you’ll find.
How to Install Joist Tape
Installing joist tape is one of the easier tasks in the deck building process. Still, there are some guidelines you need to follow to make sure it’s done properly. A poor installation job could leave your deck joists vulnerable or even make them more prone to damage than if you used no deck joist tape at all.
Step 1 – Surface Preparation
Make sure the deck joists are dry and clean. For most of the tapes on this list, you’ll need to install the tape when the temperature is 40 F or warmer. TimberTech is the exception. Unless you’re installing deck joist tape on another planet, you should have no problem meeting its -70 F to 200 F installation range.
Step 2 – Measuring the Tape
There are two ways of doing this. Measuring the length of the joist and cutting the tape to that length, or rolling out the tape while peeling off the backing, then cutting it when you get to the end of the joist. Unless you have a couple of sets of extra hands to help you hold the tape taught as you measure its length, the latter method may work better.
Step 3 – Applying the Tape
Peel away the backing and begin applying the tape as you work your way down the length of the joist. Center the tape, making sure to leave an equal amount of overlap on either side of the joist.
Slightly stretch the tape to prevent wrinkles and bubbles. Make sure to apply pressure to the tape to get the adhesive to firmly attach to the wood. Make sure to overlap the tape at joints between the joists. Don’t leave any uncovered gaps.
Step 4 – Fold Edges Over the Sides
Once you’ve reached the end of the joist, cut the tape. Then go back and push the tape overlap down, so it firmly attaches to both sides of the joist. Cut the tape at corners to allow it to lie flat.
Step 5 – Smooth Tape
Use a roller to smooth out the tape and ensure it adheres well to the wood.
Joist Tape Alternative
Although joist tapes offer an excellent way to waterproof your joists, they aren’t the only option out there. If taping the tops of your deck joists doesn’t sound like the solution for you, then consider these other options:
Seal Deck Joists
Sealant provides more comprehensive protection than deck joist tape as it involves protecting the entire joist by coating it in deck sealant. Just keep in mind that this method is considerably more time-consuming. It also may not be as long-lasting as the sealant will wear away faster than deck joist tape.
This method offers perhaps the best protection for your deck. It involves covering the joists in a thick rubber sealant. As liquid rubber has the consistency of tar, this process is time-consuming and messy. It also leaves an unattractive finish.
Coil stock protects your deck’s joists with the strength and durability of metal. Just keep in mind that the installation can be a bear. You’ll need special tools or some creativity if you use this method.
A great option if you like the strength of metal but want a simple install. You’ll still need to use tape at the joints, though or this fix could create more problems than it solves.
Old Motor Oil
If you do your oil changes, then you probably have more than a few containers of old motor oil sitting around. Recycle that old oil by using it to waterproof your joists. It’s a time-consuming method, but it’s also free.
With all the different varieties of deck joist tapes on the market today, it can be a confusing process to figure out which one is best for your deck project. I hope this guide has helped you to make this process easier.
Perhaps the only wrong choice is to use no tape at all. Any of the tapes on this buying guide will do an excellent job of preserving your deck framing for many years to come.
And, if tapes aren’t appealing to you, I hope you check out my article on the many options you have for protecting your deck’s joists.