Curious if anyone’s tried using self-sealing tape over truss tops before laying composite?
I’ve actually skipped the self-sealing tape on a couple of my own decks and haven’t seen any major issues yet, even after several years. Maybe it depends on climate—here in the Midwest, we get freeze/thaw but not a ton of standing water. I do wonder if adding tape might trap moisture against the wood instead of letting it dry out. Sometimes a good slope and proper spacing does more than any barrier. Just my two cents...
I’ve used the self-sealing tape on one deck and skipped it on another. Honestly, the taped one does seem to keep the joists looking newer, but I get what you’re saying about moisture. Here in the Northeast, we get a lot of rain and snow, so I figured it was worth the extra step. Haven’t noticed any trapped moisture issues yet, but I do make sure there’s a slight gap at the edges for drainage. Maybe it’s overkill, but I’d rather not deal with rot down the line...
I hear you on the overkill thing—my uncle’s the king of “good enough” and he just slaps the boards down, no tape, calls it a day. But I did the tape on my own deck last year (also in the Northeast) and honestly, it’s holding up way better than his. Only thing I noticed is if you don’t leave that little gap at the edge, water just sits there...and then you get that gross green stuff. Not fun. I’d rather spend an extra hour taping than deal with soggy joists later.
I’ve seen the taping method work out pretty well for some folks, but I’ll admit I’m a bit on the fence about it. I manage a few properties in the Northeast too, and we’ve had decks done both ways—taped and untaped. The tape definitely keeps the joists looking fresher, at least for the first few years, but I’ve also noticed it can peel or curl up if it’s not installed just right. Once that happens, water sometimes gets trapped underneath, which ends up being just as bad as not taping at all. There’s something about freeze-thaw cycles here that seems to mess with adhesives over time, especially on the north side where sun doesn’t hit as much.
One thing I lean on more is using pressure-treated lumber for the joists and making sure there’s a consistent gap between the boards—at least 1/8" or so. Even a little less if you’re using composite, since those can expand. The gap makes a huge difference for drainage. I’ve seen decks without enough spacing, and you’re right, the green slime and rot show up fast. But I’ve also seen a couple taped jobs where the tape failed and it actually held moisture against the wood. That’s a pain to fix once it starts.
What’s worked for me is focusing more on airflow under the deck and keeping things clear of debris. I know it’s tempting to go all out with products and “extras,” but sometimes just the basics—good spacing, solid flashing, and regular cleaning—keep things in better shape long term. Not saying tape is a waste, just that it’s not a cure-all. If you’ve got a deck that’s low to the ground and doesn’t get much sun, maybe the tape is worth the extra effort. But for higher decks with decent airflow, I tend to just stick with tried-and-true methods.
Kind of funny, though—every time I walk by one of those “good enough” jobs, I half-expect to see sagging boards and rot, but sometimes they hold up surprisingly well... Maybe luck, maybe just old-school wood.
- Gotta say, I’m still a fan of the tape, even with the risk of it peeling up sometimes. Maybe it’s just me, but I’d rather deal with a little adhesive drama than watch another joist rot out from the inside. Had one deck where the tape was still holding up after 8 years—north side, too. Maybe I got lucky, or maybe my kid’s “help” with the roller actually made it stick better.
- Noticed the same thing with gaps—if you skimp on spacing, you’re basically inviting a swamp under your boards. But I’ve also seen folks get a little too generous with the gap and end up dropping their keys (or worse, their phone) through the cracks. There’s a sweet spot, and it’s not always what the board packaging says.
- Airflow’s huge, but I’ve got a low deck that’s basically sitting on the ground. No amount of “old-school” is saving those joists without some kind of barrier. Tape, paint, or even that fancy liquid rubber stuff—it all helps a bit.
- At the end of the day, I feel like half of it’s science, half’s just crossing your fingers and hoping the weather’s on your side.