I'm currently renovating my bathroom, and I've removed the plywood subfloor to access the crawlspace for some repairs. I plan to add sister joists to the existing ones, but I want the new joists to sit half an inch lower. My idea is to cut the new subfloor sections to rest on these sister joists, making everything level with the current joists. This way, I can install durock sheets and tile without creating a half-inch step between the bathroom and adjacent rooms. Does this approach make sense? Are there any potential issues I should be aware of? Note: the existing joists run the length of the bathroom, which is an addition to the house.
4 Answers
It's a tricky situation; I wouldn't cut the joists down without careful planning. If you're determined to lower it, just be aware that maintaining structural integrity is crucial, so consult a pro if you can! Might be worth it to deal with a slight transition rather than risking a problematic floor.
I've seen it done for shower transitions, but doing it for an entire room could complicate things. Make sure to add lots of blocking to avoid any flexing with the tile, and keep an eye on stability if you're going this route.
It might be possible, but without details about your joists' size and spacing, it's hard to guarantee. If you check joist span tables and see that you can use the next lumber size down, you should be fine. A small transition strip isn't a big deal if needed, and using wood blocking along with thinner cement board can help blend things at the doorway.
Lowering the joists like that can lead to issues, mainly with tile cracking due to floor movement. It's best to consult an engineer before proceeding, especially to ensure the sistered joists are properly sized and supported. If you're set on this plan, consider cutting them down carefully to ensure you don't compromise the structure; adding blocking can also help prevent flexing underneath all that tile.