I removed my bathroom floor, toilet, and shower/tub combo due to water damage. Some of the floor joists have some water damage as well. In reading here about sistering floor joists, I should sister the joist two feet past the existing water damage on each end. When that is done, should I cut out the water damaged portion of the joist and replace it? What if the joist is a double joist (main beam) and only one of the 2x8 is damaged?

The new joist will take the place of the damaged joist and carry the weight of the floor. The new joist must sit on the same wall or foundation as the old joist. You don't need to replace or remove the damaged one. Just nail or screw the new one to the old one away from the damaged area. Nail or screw it into the top plate of the bearing wall or the sill plate of the foundation. Look down both edges of the new joist and you will see a crown or slight bow outward. Put that crown up.

Hi George,

Magprob is right.

You can get away with going a few feet past in some cases, but this is never desirable.

If at all possible, you want to be able to end the new joist over the first perpendicular walls in either direction from the damage, which is probably where the old joist terminates. I would then glue them togeter and screw them.

Don't attempt to cut out the old joist. Allow it to dry thoroughly, and spray it with a bleach solution to kill any mold you might be harvesting.

Once the source of moisture is gone(the leak), your potential for mold & mildew goes with it.

Thanks,
Json

Sorry Schwim but I got to soread some around before I can give you another compliment. Both you nguys used a right approach.
Bo