The simplest and easiest way to extend the life of your deck joists is joist tape. Which is why is one of my top picks for ways to prevent deck joists from rotting. The value of joist tape is huge, especially for wood joists under composite decking. It helps the joists to last at least as long as the decking, if not longer.
Having rebuilt many decks and it is almost always the top 2″ (50mm) of the joists that are rotten. Joist tape prevents this by protecting the most vulnerable part of the deck joists.
“What is Joist Sealing Tape?
Joist sealing tape is a waterproof protection for joists. A permeable membrane with a self-adhesive layer for ease of installation and permanent application.”
Which has become even more important with the reduction in level of treatment of pressure-treated wood in the last 20 years.
Your parents may not have needed to install joist tape, but your deck will definitely last longer if you do.
Best Deck Joist Tape – Our Top Recommendations
So, before any more talk, here are my top 3 picks for joists flashing tape.
This is not an exclusive list. There are many other brands of joists tape available on the market. Some may work better for your deck project or giving the specific conditions.
Some of them have not been included simply because basic internet research and product descriptions rule them out.
Others simply are more a regional brand. Resisto a Bitumen is such a joist tape. I have installed hundreds, no probably 1 000 of feet of this joist tape because of it price. It is one of the cheapest priced joist tapes with decent performance that I know of. But for most of you, you will not be able to order it. Therefore I did not include it.
Still, others were simply a matter of budget. I would love to be the Wirecutter with its millions to spend on product research, but I am just a deck builder with a keyboard. So, I had to limit my research to ones that seemed most likely to offer value while still fitting in my budget.
But research I have.
- Spending hundreds on buying the tape. Thousand if you include all the tape I have installed over the years.
- Installing the tape.
- Evaluating the tape.
Everything we would expect from a review of the best joist tape.
These are the 8 joist tape brands reviewed, plus other brands which may not be available in your market.
To make comparison easier, I have grouped them into material types.
The 3 most common joists tape materials are
Each material has its own advantages and disadvantages.
Bitumen Joist Tape
Borrowed from roofing. Most Bitumen tape were originally designed for roofing applications. Therefore they are very effective in blocking water and are often more economical than other options.
Has a chemical reaction with PVC decking. Do not install under PVC decking.
- Waterproof, sealing of the top of the joists
- Quickly sticks to the joists
- Self heals around minor penetration, preventing water from penetrating through screw holes
- Large range temperature range for application
- Resistant to chemicals, so will not react with joists, hangers, etc.
- Economical protects your joists for less
- High levels of off-gassing (It stinks)
- Loses adhesion after freezing
- Cannot be reapplied and will stick to itself
- Will dry out over time
- Will react with PVC decking
Butyl Joists Tape
A more rubberized material designed to not react with composite or PVC decking material. Making it safe to use for all decking. This is probably why major composite decking brands like TimberTech, Deckoraotors and Trex recommend and manufacture butyl tape.
- Really sticky, especially during initial installation
- It is waterproof, which is the whole point of joists tape
- Effective in sealing around screw penetration
- More sensitive to temperature change, limiting application
- Breaks down under direct exposure to UV, Sunlight requiring protection (Decking to be installed soon after installation
- Can darken because of oxidation, but this is rarely a problem under decking.
- More expensive variety of joists tape
Acrylic Joists Tape
Thinner than butyl tape, making installation easier. Safe to use with composite and PVC decking. My top pick is also Dr. Decks’ top pick for his amazing decks that he builds.
- Sticks better than most other tapers
- More resistant to extreme temperature, UV, chemical and oxidation
- More resistant to fading. Black stays black.
- Smells less. Considered more environmentally friendly with less off-gassing
- During installation can be pulled off and reapplied
- Safe for PVC decking
- Takes 1 to 3 days to fully set
- Does not allow the wood to breathe, can trap water
Bitumen Deck Joists Tape Reviews
The biggest advantage of this category is price. Joist tape made from other material will cost more.
1. Grace Vycor Deck Protector Self Adhered Flashing
Simpson Strong-Tie®, yes, the company that makes most hangers that we build decks with has elevated Grace Vyvor to ensure the two products work well together. Vycor has been confirmed to protect hangers against the corrosive property of wood treated with CCA. So not only does Vycor protect your joists against rot but also hangers against corrosion. (Zinc coated hangers will not react with CCA)
- Trusted name in flashing material
- Release paper easily pulls off
- Thick (25 mils)
- Good Seal around screws
- Limited Product replacement warranty
- Marking on tape
- Poor adhesion
- 4″ x 75′
- 9″ x 75‘
2. Cofair DFB375 Deck Flash Barrier
Cofair is a popular flashing brand. Making many other construction sealant products from driveway sealers to roof tape. If you need to keep water out, Cofair has a product for you.
One of their biggest advantages is price. Cofair consistently offers quality but economical products.
- Protects against CCA corrosion
- Great Adhesion
- Less rubberized, it can easily wrinkle
- Needs to be protected by the decking against UV
- 3” x 75’
- 12” x 25’
3. DeckWise WiseWrap JoistTape
A company specializing in deck construction and maintenance products. As there name says.
Deckwise is passionate about decks and deck flashing is just one of many products that the manufacture to help you build a better deck.
- “Super Grip” rubberized asphalt adhesive
- Excellent sealing around screws
- Matte black, no marking
- Thick 35-40 mil thick
- Limited Temperature application (40°F/5°C+) or warmer
- Ironically doesn’t stick well to the edge of the joists
- 3” x 75’
- 12” x 25’
Butyl Deck Joists Tape Reviews
Flexibility and strength are Butyl best qualities. Making it an excellent material for joist tape.
4. Imus Seal Butyl Joist Tape
Imus Seal is a brand trusted by contractors, roofers, and DIYers alike to help better protect wooden construction materials from wind, weather, and the elements.
- Imus Seal butyl joist tape self-adheres to joists and beams, providing effortless protection against water and weather
- Effectively diverts water away from wooden joists and beams to prevent rot and degradation
- Excellent weathertight seal between wooden and metal construction materials
- Works just as well with treated and non-treated lumber materials
- Tear-resistant release liner
- Can be a little tricky to install at first
- Somewhat temperature-sensitive (30-120° F/ -1°-49°C)
- 1 5/8” x 50’ feet long
- 4” x 50’ feet long
- 6” x 50’ feet long
5. Trex Protect Joist Butyl Tape
From the maker of one of the most popular composite decking on the market, Trex. Another quality butyl tape is made specifically for deck joists. Tried and recommended for Trex decking along with other composite decking brands.
- Brand name
- 20-year warranty
- Matte black colour (no marking)
- High adhesion level (very sticky)
- Pricey compared asphalt tape
- Stick to itself, making application harder
- 1-5/8″ x 50′
- 3-1/8″ x 50′
6. TimberTech PRO-Tac Flashing and Joist Tape
Another quality brand making both composite decking and joist tape to protect the joists under it.
- Trusted brand name
- Large temperature application range (20˚to170˚F/-7° to 77°C)
- Will not pull off when installing decking
- Thicker than other tapes (28.5mil)
- Excellent seal around screws
- Black, no marking on tape
- Expensive compared to other Butyl tape
- Thickness makes it harder to work with
- 1.625” x 65’ length)
- 2.5” x 65’ length)
- 3.25” x 65’ length)
- 4” x 65’ length)
- 12” x 25’ length)
7. Cofair BDFB1550 Butyl Deck Flash Barrier
Cofair is one of the few brands on this list that offers both a bitumen-based joist tape plus recently a butyl. Giving you more choice for your deck needs.
- Low VOCs
- Low-Temperature application (25°F/-4°C)
- Self-seals around screws
- Needs to be protected from the sun (UV)
- 1 5/8” x 50’ long
- 3 1/8” X 50’ long
Acrylic Deck Joists Tape Reviews
This is my favourite joist tape to work with. Most likely because it’s so much easier to work with than bitumen tape, the more economical option.
It is thin, making it easy to apply. But the biggest advantage is its adhesion. It easily sticks to the joist but can be pulled off and reapplied with minimal fuss. But best of all, it sticks to the joist like few other joist tapes, even for the second or third application.
8. Nichigo G-Tape™
Recent tests have show to maintain 60% of its adhesion after 50 years and 100% tensile strength.
A polyethylene-based flat yarn substrate, creating a high tensile strength with superior adhesion.
- Can be torn ripped by hand but still has a tensile strength
- Leaves no residue if adjusted within 1 hour of application, and can be reapplied.
- Doesn’t stick to itself
- Doesn’t require a primer
- Lighter than Butyl or Bitumen Flashings
- Can be applied at -20° F/-29°C to cold for fingers but okay for G-tape
- Low VOCs
- Durable up to 300 days of UV exposure
- Black in colour with no marking
- Thin, only 9.4 mil Thick
- Less sealing around screws than butyl tape
- 2″ x 65′ long
- 4″ x 65′ long
- 6″ x 65′ long
- 9″ x 65′ long
- 12″ x 65′ long
Now when selecting the best deck joist tape, I evaluated them using these criteria’s
Joists Tape Buying Guide
Primarily you want a tape that will last, is easy to install, and won’t break the bank.
You want a tape that sticks well to the wood with minimal frustration but can still be adjusted. Will it stick to itself once the paper has been removed?
Ideally, you want a tape that is easy to cut or tear. Making installation quicker.
The thicker the joists tape is, the better it will seal around screws. Limiting water penetration.
- Acrylics are some of the thinner joists tapes
- Bitumen is often thicker.
- Butyl is in the middle
But keep in mind that thicker tapes are harder to install. Giving an advantage to thinner acrylic tapes.
Where you plan to use the tape impacts, the requires different tape widths.
Wider tape is better for protecting flat blocking.
For joists, you want a minimum of 1 5/8″ (41mm). Personally, I prefer the higher protection of 3-4″ (75-100mm). The larger sizes creating wings to fold over protecting both the top and the vulnerable top inch of the joists.
For beams and flat blocking 6″ or 9″ (150-230mm) width protects better and is quicker to install. The wide width can also be used to cover the wood rim joist before installing a composite fascia board.
Flat blocking is the most venerable part of the deck’s substructure. As the wood is flat, collecting water increasing rot. If you can’t protect the entire deck substructure, protect the flat blocking with joists tape.
How long is it?
This seems trivial but does impact how many rolls you need to buy. How many seams there will be on the deck.
And of course, the all-important price. Longer rolls may cost less per foot.
Not all tape is the same, nor does it cost the same. The tricky balance paying the least but installing the longest-lasting, most protective joists tape.
But do keep in mind, joists tape may seem like an extra expense, increasing the cost of your deck without adding any fun features.
Which is true but like a roof that doesn’t leak. The cost of joists tape is small compared to the cost of rebuilding a deck prematurely or replacing a rotten joist under your composite decking.
Once installed, you may never know what brand of joists tape you used. But the brand can reflect how long it will last, its warranty and if it was designed for your composite decking brand.
How to Install Joist Tape
Step 1 – Joists Preparation
Water and dust will prevent the tape from sticking.
So, make sure the joists are dry before applying the tape. Nothing special. If the wood is dry to the touch, it’s dry enough.
Also, brush off any sawdust or dirt that may be on the joists. You could use a small brush to sweep away any sawdust from construction. I like working with gloves and simply rub-down the joist, brushing off the sawdust with my hands.
Then you are good to go.
Step 2 – Measuring the Tape
This really does not need to be done. You are better starting the tape on the joists by the ledge and working away from the house, and cutting it at the end. Then it will always be the right length and save you time trying to measure.
Step 3 – Apply the Tape to the Joists
Pull off about 6″ of the backer paper and position the tape on the joists overlapping the ledger and flashing. Once firmly pressed into place, roll out another 3′, or your arm span. Centring it on the joists. Pull the tape a little to remove any wrinkles, and then pull the paper off. Then press the tape onto the joists with your hand or roller. Then continue till the end of the joist.
Cut the tape with a utility knife.
Step 4 – Fold Edges Over the Sides
Cut the overhanging tape at 45° where the joist, blocking, or rim meet. Then fold down the overhanging tape and press firmly to the joists.
The good tapes will cleanly stick to the joists. The cheaper lower quality tapes may need to be stapled on or be okay with wings.
Step 5 – Smooth Tape
This can be done either by hand or with a roller. The idea is to push the tape onto the wood for a tight seal and better adhesion. Along with removing any little wrinkles.
Roller-gives the most consistent levelling. After setting the tape on the joist run the roller with slight pressure pushing the taping down activating the adhesion, while pushing it into the wood fibres.
By hand-is my personal choice. Same as the roller but use your hands to push the tape tight into the wood. Running your hands along the top of the tape will produce friction and heat. Wearing gloves is a great idea. Gloves will also protect your hands from slivers.
Why do You Need Joist Tape?
Deck joists need tape to prevent water penetration into the joists. This is the most important reason for joists tape. An impermeable barrier against water penetration, protecting the wood from rot. It does this in a number of ways which we will go through.
Shelters the deck joists from water
Like shingles on your roof is joists tape to your deck. It diverts rain and snow off the joists. Keeping the joists dry preventing rot.
It may not seem like much but just think of al the damage your house would have it didn’t have shingles diverting the rain off your roof and house.
Deck joists may look like they are fine outside in the rain. If the water quickly runs off, leaving no harm. But this just isn’t true.
To keep the joists dry, you need to divert the water off the joists. Joists’ tape being impermeable to water does exactly that. Diverts the water of the joists, keeping them dry and rot-free for years to come.
Seals Around Decking Screws and Nails
Like a tattoo needle injecting the ink under the skin. The hundreds, thousands and decking screws are doing the same. Every penetration point into the joists is one more place that the water can sneak into the untreated wood and start to rot.
Even if you use pressure-treated wood joists, the treatment is only on the surface. Even incised wood which often is done for higher-treated wood for ground contact, is still only on the edges of the joists.
The screws penetrate deeper than the treatment giving the water and fungi access to the raw untreated wood. Wood that can quickly rot.
Keeps Fungi and Gunk off the Wood That Builds Up Between the Decking
Gaps between deck boards allows water to run off the deck. Plus, room for the decking to expand and contract, which is essential for most composite decking, especially PVC.
But dirt can collect in the gaps. Which adds the second element required for fungi and rot. A source for the spores to grow. The gunk collecting fungi spores can quickly grow once the sun comes out. Once the rot takes root, it can be next to impossible to remove from the joists.
The opposite of landscape fabric under the deck which prevents plants from growing by blocking the sunlight from reaching the plants.
Joists tape prevents rot by preventing fungi spores from accessing their food, the wood of the joists. Keeping the joists safe.
Reduces Walking Noise on the Deck
One of my customers mentions this, I haven’t done any hard research to prove it, but it makes sense. Just like underlay under laminate flooring, which minimizes the click of the wood. Joists’ tape could do the same.
Decking should be screwed down, which limits movement, unlike a floating flooring, but there is still some movement.
There is special acoustic design joists tape for interior application. Deck joists membrane is not the same but may have a similar benefit on your deck.