Joist Tape: What is it and Do I Need it?

Why a Deck Is More Than Outdoor Space

Adding a deck to your home is not just a matter of adding some outdoor living space. Although its basic function is again to serve as exactly that. It is also a culmination of your years of hard work, toiling away for hours upon hours. A deck is not just an outdoor living space but it is also a reward for all of the hard work that you have done over the years. Consider it the ultimate retirement package. I mean who hasn't fantasized about lounging on your deck with a nice cocktail in hand and sitting on your deck chair while you gaze at the beautiful sunset with your loved ones. 

It is quite frankly an investment, not just in metaphorical terms that it gets you comfort and safety but also literally it adds a feature to your house that adds value to your estate too. So if you ever plan on selling your house, you can market the deck as its value proposition and there might even be buyers for whom the deck is a major deal maker.

For your average 400 square foot deck, it can cost you around $12,000 to $24000, if you go for composite decking. For wooden decking, it can be around $5,000 to $17,000 and for stone deck is pretty much similar to your composite decking.

As you can see, it is quite literally a lot of investment when it comes to installing a deck to your house to create some more living space for yourself. These prices do not include maintenance costs for your deck tiles as some materials of deck tiles such as Composite decking and wooden decking might require more maintenance compared to tanzanite stone decks. Be mindful of these recurring costs when you are choosing the decking. 

Why do we need Joist Tape

No matter what your decking is, your deck substructure would most likely be made of wood. There are many ways to protect your structure against the forces of nature. Your deck substructure is very likely to split and rot about 8-10 years after it is installed. After all, it is wood, although it has been treated rather well to withstand the exposure for such a long time, it will still crack, warp and rot. The boards that are supported by your substructure would probably last about 25 years. If you want your deck to be safely supported by its substructure for the life of the deck, you can protect your investment for a minimal extra cost. 

Joist tape is one very affordable way of protecting your deck substructure for pretty much minimal cost. It is a peel and stick flashing tape that allows the wood to breathe because it is applied as a proper coverage on top of your joists and beams. The purpose of this tape is to wrap around your screws and bolts and to act as a barrier against any moisture whatsoever. Joist tape will protect your substructure from decay and it will guarantee that your foundation will last as long as your decking will. 

Read more: Deck Railing Designs 

What to shop for in Joist Tape

Here are some things that you should consider when you are shopping for the right kind of joist tape to protect your investment. 

Material: Asphalt and Butyl are two main types of Joist Tape. You should look for a butyl tape because it has significantly lesser high temperature oozing, it will endure less stain and its adhesive quality allows it to stick to a wider range of surfaces quite easily. It can also be applied for a much wider range of temperatures as its chemistry allows the adhesive to tread into any surface no matter what. It also creates a much tighter seal around your deck screws to prevent moisture from seeping in. 

Ease of Installation: Butyl tape does not require as much trimming because it lies very directly over the board, This means it requires little to no cutting and minimal overlaps. This makes it very simple and quick to install. Also as mentioned before, the adhesive quality on these are great meaning you won't have to take it off to make adjustments again and again. 

Thickness: The Tape that you select should be a perfect fit on your deck tiles. A tape that is a bit too thick can make it much harder to install as it will require trimming and also if it is too thick then it can even create an uneven surface which although wouldn't be much of a tripping hazard but is very uncomfortable to step on. 

Price: You want to have a joist tape that is affordable, but you are also looking for one that is high quality. There is a very obvious quality/cost tradeoff at play here where the higher you pay the more durable your tape will be but there are brands that offer much more value for what you pay. Remember that your tape is almost like insurance on your deck substructure. 

Reputation: There is a reason that people gravitate towards certain brands more which doesn't just boil down to marketing but also to the fact that these brands actually deliver on the promises that they make. For each type of tape, such as butyl tape there are several brands that would offer their own solutions to it. Be sure to check in with your local hardware store and ask for opinions about them.

FAQs about Joist Tape: What is it and Do I Need it?

What is joist tape—and what does it do?

• A self-adhered flashing that caps joists, beams, rim/ledger and self-seals around fasteners to block water, helping prevent rot and moisture intrusion into the frame.

Do I really need joist tape?

• Not mandatory, but it’s a low-cost upgrade that can extend substructure life and reduce callbacks; some products also cut connector corrosion with modern PT lumber.

Which is better: butyl or asphalt (bitumen) tape?

• Butyl typically wins for decks: less high-temp oozing, stickier, wider install temp range, and tighter seal around screws than asphalt.

Where should I apply it?

• Cover any surface that can hold water: all joists, double-joists/beams, rim joists, steps, stair stringers, blocking, the ledger, and even under joist hangers per brand guidance.

What widths do I buy?

• Common sizes: 1-5/8 in for joists and 3-1/8 in for double-joists/beams (brand example: Trex Protect). Wider rolls exist for ledgers/beam tops

What temperature can I install at?

• Follow the label. Typical guidance: ≥50°F/10°C for best adhesion (Trex); some butyl tapes allow installs down to 25°F/-4°C (DeckWise, Vycor). If cold/wet, tack/staple until temps rise.

How long can the tape sit in the sun before covering?

• Limit UV exposure—many butyl products say ≤90 days before covering with deck boards/fascia.

How do I install it correctly (quick steps)?

• Clean & dry framing → peel and press firmly along tops → wrap edges (slit corners) → roll tight → trim. Start at low points and continue across joists, beams, ledger, rim.

Is joist tape compatible with pressure-treated and composite decks?

• Yes—look for tapes listed as compatible with PT lumber & composites; several brands specify this directly.

Is joist tape required by building code?

• No explicit IRC requirement. The IRC deck section (R507) focuses on structure, spans, connections—not joist flashing tape. Treat it as best-practice rather than a mandate.

What does it cost for a typical deck?

• Ballpark: ~$50 materials for a ~400 ft² deck (Vycor example), and often “under $100” total per consumer guides—cheap insurance relative to deck cost.

Does joist tape help with fasteners and metal connectors?

• Yes—quality tapes self-seal around screw/bolt penetrations and can reduce corrosion rates on galvanized connectors used with modern PT lumber.

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