Fixing water damage on ceiling below bathroom. What are next steps?

Question

I just noticed what appears to be a water stain with some peeling paint on a first floor hallway ceiling underneath a second floor bathroom. The stain appears to be below the toilet and does not feel damp or wet. I checked the faucets, shower and toilet in the upstairs bathroom, none seem to be leaking. What next steps should I consider to fix this and stop damage from getting worse? Picture below.

Background: I'm a first-time homeowner who just moved into a 1960s-built house earlier this month. New to doing repairs myself, didn't grow up with family members who taught me and am learning from square one.

Answer 1

You need to pull the toilet and see if the seal has been leaking.

Have a new seal ready. If you pull the toilet you need to install a new ring. unless it has a foam seal.

It could be that since you moved in and started to use the toilet regularly, the seal that seeps a little water with occasional use, now seeps often daily. the result is more water and the leak manifesting itself on the ceiling.

Fix the leak before repairing the ceiling.

Answer 2

My Suggested Procedure

1. Cut away that portion of drywall in the ceiling that is damaged and have a look. It will need to be replaced anyway. But just cut away a nice square or rectangle with the damaged part - doesn't need to be much bigger.
2. If it is the toilet, then uninstall the toilet. You won't know exactly what the issue is until you lift it up and see, but you'll probably find that you need a new seal (wax or one of the new wax-less kinds). I like the new wax-less kinds (the installation is more forgiving), just follow the instructions on the package to install that.
3. If the toilet is not the problem but a pipe under it is, then it's a pipe repair job. It would be hard to give details about a repair without seeing the exact situation - if this is the case, just post another question to the forum, preferably with pictures. Drop a note in this question to point to your next question so we know they're related.
4. If the flooring OSB around the toilet is damaged, you'll need to look into that too. If it is just lightly damaged, then maybe let it dry, spray-paint some Killz on it, and go with that. If it's really damaged, then you may have to cut away the damaged portion, but this might quickly lead into the bathroom flooring. That would be worth another question on the forum.
5. To repair the ceiling, cut a 2x4 to about six inches longer than your ceiling hole. Stick it up into the ceiling and lay it across the hole and screw it into place where it overlaps the drywall (make sure your screws embed into the drywall a bit and don't stand proud). Then cut a drywall patch to the dimensions of your hole (make sure you get drywall of the same thickness as the existing ceiling!). Screw the patch into the 2x4. Mud, sand and paint.

Addendum

To lift a toilet, here are the steps:

1. Turn off the water valve.
2. Flush it.
3. If the toilet was caulked to the floor, run a razor blade around the base.
4. Get some towels - old ones are better.
5. Unscrew the water feed line from the tank. Some water may dribble out.
6. Remove the caps and unscrew the two nuts on the bottom of the toilet.
7. Get a friend. Toilets are a bit heavy and awkward for one person.
8. Wrap towels around the toilet, especially around the back.
9. Use your friend to lift up on the toilet. Oh ok, you can help too.
10. Water will slosh out with handling, especially if you tilt it back. That's what the towels are for.
11. If you find yourself looking at a wax seal, then it will need to be replaced anyway - they can only be seated once.

To re-install, basically do the steps in reverse.

Recommended Tool

If I may make a recommendation to a first-time homeowner, I suggest looking into a Dremel Oscillating Tool. It will make nice clean cuts in drywall and wood (even 2x4's), and in tough-to-reach places too.