Using a double-threshold shower pan in a 3-wall alcove? Drain/joist issue complicating things
I’m in the middle of an alcove shower remodel and could use some opinions before I go too far down the wrong path.
The plan is a pretty standard setup: prefab shower base, cement board, and PVC wall panels. The space is 56” x 36” and it’s a 3-wall alcove.
Here’s where I messed up — I already bought a DreamLine SlimLine 54x36 pan, but it’s the double-threshold version (meant for a 2-wall / corner install). So now I’ve got a pan with no flange on one side going into a 3-wall setup.
I’m debating whether I can still use it and just properly seal/waterproof that “open” side against the wall, or if that’s asking for trouble long term.
Normally I’d just return it and get the correct single-threshold version, but the issue is the drain location. My current drain is about 16.5” from the right wall, and my joists are at 12” and then the next one is around 27”. So the drain pretty much has to land between those.
If I keep this pan, I only need to shift the drain a few inches. But every single-threshold pan I can find in this size has the drain either centered or pushed to a side that would land right on top of a joist or on the other side of one, which I really want to avoid.
So I’m stuck between:
Using the double-threshold pan in a 3-wall alcove and figuring out how to properly waterproof that flange-less side
Or returning it and dealing with a much bigger drain relocation problem (cutting into or through a joist, which I’d rather not do)
Has anyone run into this before or made something like this work reliably? Is sealing that wall a reasonable solution if done right, or am I just setting myself up for leaks later?
Appreciate any insight — trying to make the smartest long-term call here