Do I Need To Sister This Joist?

Remodeling my master bath and I'm swapping the tub and shower. When I pulled the old garden tub and the platform around it, I discovered that they had notched the floor joist to make room for the drain.



This notch is ~2.5" deep and 3.5" wide and darn near in the center of a 15' long 2x10 floor joist and will end up under the new 54" square shower. At first I didn't think much of it, but after reading up on what notches are acceptable, this one clearly is not. I don't want issues down the road with sagging and aligning the shower doors so it seems like I should sister this to strengthen it.

This addition is relatively young (2006) and while the floor isn't completely level, it doesn't seem to have sagged.

Am I right that this should be sistered and if so how far past the notch on each side should I go?

 

Yes, it should be sistered. You need an overlap of at least 24" on either side but more is better. Hopefully you can get at least 3' on either side.

 

I should be able to get at least 6' in there.

Second Q, the reason I'm doing this remodel is there was a leak at the shower through to the crawl space. There was some subfloor damage and three joists show water staining.



Again, I wasn't concerned as they seem sound, just stained. I think that is true of the near one and the far one. The near has a rotted section like a notch, maybe 1.5" deep and 6" long. But it's 18"-20" from the end of the joist and the staining isn't that deep. The far is only stained on top, no obvious rot or splitting.

The middle, however, obviously saw the bulk of the water. It's complete, but there is separation of the grain. There's also a tall, shallow cut in this joist they put in for clearance to the old shower drain (whoever originally built this obviously didn't plan ahead).



Even though this is only ~40" from the end of the 15' joist, I'm wondering if it should be sistered too? The tub will be going here (you can see the drain location), with the end of the tub about where the far joist is. This is a different joist to the first one.