How can I effectively protect the wooden subframe of my composite deck from water damage while maintaining a balance between sealing and allowing it to breathe?
Asked by Calvin Cox 
3 months ago
Last Updated: September 29, 2024
I’m in the process of getting a composite deck with a wooden subframe built and I want to make sure I can handle keeping the wood protected from water on my own. Any advice on how to go about this? I was thinking about using joist tape to cover everything, but that might be overkill, right? Would an opaque stain or sealant be a better option? And if so, do I need to apply it to every surface or leave the underside untreated for ventilation? I like to think of myself as a DIYer, but I’m realizing I might need some guidance on the basics.
Make sure the pressure treated lumber is completely dry before applying Thompson’s or a similar sealant. The most important thing to check is if the posts are well supported by the concrete they are set in.
I believe so, since they’re not directly on the concrete.
Using that bracket is correct.. I just hope it’s thick enough to support the weight. And those screws are not the right ones… my bad 😅
Oh, well, I’m not sure… I’m currently struggling with DIY staining, haha, so building the deck myself is definitely out of the question. A well-known company is handling the construction, so I assume they’re following all the necessary regulations, but you never know. 🤷♀️
It seems like they just placed the post on an old patio slab. It might be okay or it might not, hard to say. If you’re in a cold climate, it’s likely to shift quite a bit. Without seeing the slab, it’s really impossible to know for sure. It could be completely fine if it’s a thick slab on a solid base. I’d recommend asking them about it.
You really just need the deck tape shown in the photo under a deck. If you plan to stain it, make sure to wait 6 months to prevent chemicals from the pressure treatment causing the stain to bubble off. Thompson’s Water Seal is a paraffin treatment that will wear off due to weather, especially on horizontal surfaces in a few months and vertical surfaces in about a year.
Oh my goodness! Thanks for sharing this… I was actually planning on staining this weekend. 🥲I guess I’ll wait a bit.
Gotta make sure the moisture content is 15% or lower, that’s my go-to. You can grab a moisture meter at any hardware store for cheap.
If that’s pressure treated wood, and it sure looks like it, I wouldn’t bother using tape. In my experience, that stuff can actually accelerate rot by trapping water. Once you start screwing in the decking, it’s going to end up full of holes. I think that product was just created to sell something, but it’s unnecessary if you use the right wood for your frame.
Was on board with the idea.
The joist tape is sufficient as is. If necessary, you can reseal the wood once it dries. That deck is built to last over 30 years 🙂
Maybe wait until next spring when it’s fully dried out before staining it if that’s something you’re interested in. It’s looking good as it is right now.