Quick verdict
Ten rolls of 2 inch wide self-adhesive butyl tape, 500 feet in all, that cap the tops of deck joists, beams and ledgers so water cannot sit in the screw holes and rot the frame from the top down. Butyl seals around every fastener and stays flexible in heat and cold. A 2 inch width covers standard 1.5 inch framing with overlap. Joist tape is the cheapest way to double the life of a deck frame, and this pack does a whole deck for the price of two branded rolls.
Strengths
- Seals fastener penetrations so water cannot reach the joist
- Butyl stays flexible and adhered through heat and frost
- Two inch width caps 1.5 inch framing with overlap
- Five hundred feet covers a full deck frame
- Peel-and-stick application with no tools
Weaknesses
- Must be applied to clean, dry wood above about 40 F
- Thinner than premium 20 mil tapes from brand names
- Hard to reposition once pressed down
The overall YardToolLab Score is out of 100. Section scores are out of 10.
Where Decks Rot First
A deck frame fails from the top of the joists. Every deck screw opens a hole into the end grain, water sits in it after every rain and in ten years the joist top is soft. Joist tape stops that. JOAPRIL’s pack is ten rolls of 2 inch butyl tape, 50 feet each, that cap the joist tops and seal around every fastener. Five hundred feet does a whole deck.
This review is based on the listing specifications and on how butyl joist tapes perform on deck framing generally. We have not applied this tape ourselves and the brand is a generic importer.
Why Butyl
Butyl rubber stays soft and tacky for decades. When a screw passes through it, the butyl flows around the thread and seals the hole; when the wood moves with the seasons, the tape stretches rather than cracking. Asphalt tapes go brittle and acrylic tapes let go in heat. Butyl is what the premium brands use, and it is what this tape is made of.
Application
Wood must be clean, dry and above about 40 F. Peel the backing, lay the tape centred on the joist top, press it down with a roller or a gloved hand and fold the excess down each side. Cover beam tops, the ledger and rim boards, and the tops of stair stringers, which rot even faster. Then lay the boards and screw through the tape. On an existing deck, tape as you replace boards.
Width
Two inches on a 1.5 inch joist leaves a quarter inch to fold down each side, which is right. Doubled 2x beams are 3 inches wide and want 4 inch tape or two overlapped runs. Taping the ledger is the most important run on the whole deck, since it is the one you cannot replace.
Thickness
Brand-name tapes are often 20 mil or more; this is a lighter tape. For sealing screw holes that matters little, since the butyl flows around the fastener either way. It is more easily torn by a careless screw point, so start screws square.
Return on Investment
Builders who tape frames routinely describe it as the cheapest insurance in decking. A deck frame is most of the labour in a rebuild; adding years to it for the cost of a few rolls of tape is an easy decision.
Who Should Buy It
- Anyone building a new deck.
- Owners re-boarding an existing frame that is still sound.
- Builders who want joist tape in quantity.
Common Owner Complaints
Tape that will not stick to damp or cold wood and tears from screw points. Dry wood, warm day, square screws.
Alternatives to Consider
Trex Protect and G-Tape are the thicker branded tapes. Grace Vycor is a building-wrap flashing used the same way. Deck flashing paint is the brush-on alternative.
Verdict
Taping joists is the single best thing you can do for a deck frame, and this pack does the whole deck for the price of a couple of branded rolls. Apply it dry and warm, press it well and the frame will outlast the boards.
Full specifications
JOAPRIL 2 Inch x 50 Foot Butyl Deck Joist Tape, 10 Rolls FAQs
Deck boards are screwed into the joist tops, and every screw hole is a path for water into the end grain. Joists rot from the top first. Butyl tape seals around each screw so the hole stays dry.
Before. Tape every joist, beam top and ledger as the frame goes up, then lay the boards through it. On an existing deck, lift boards to tape.
The total length of all joists, beams and ledger. A 12 by 16 foot deck at 16 inch spacing uses about 200 feet, so 500 feet covers a large deck with stairs.
For 1.5 inch framing, yes, with a quarter inch down each side. Doubled beams want 4 inch tape or two overlapped runs.
