Any suggestions for bracing or supporting a toilet?

The subflooring is probably deteriorating (this likely from wet floor rotting the wood before your relative moved in. The extra weight just stressed the rotted wood more. Take off the toilet, tile or whatever around the toilet drain and take up that section of rotted wood, replace with plywood subflooring. Make sure the 2x6 supports have not begun to rot. If you are not carpenter handy, you'll need someone who is to do these things. Just bracing the toilet instead of fixing the flooring is not really an option, it will just allow more rot.

We had a old home, needed a new toilet. Got one it never seated correctly, and rocked. So my husband took a exercise mat ( the kind that snaps together) placed toilet on it traced and cut out a"seal". He put the toilet back on with the seal ( had to get a new wax ring) then he used a tube of Kwik caulking to run a bead around bottom so black ring didn't show. No more rocking toilet.

I agree with Thisbe De Mona. It's possible that the subfloor is damaged and needs to be replaced. This would cause the floor to be lower than the toilet flange and suspend the toilet off the floor. The toilet drain flange should be level or slightly below the finished floor. This will allow the wax ring to seal properly and the toilet to sit on the floor and not on the flange. The toilet bolts just hold the toilet in place to prevent movement and should not be over tightened.

Check the subflooring and then reinforce as needed, buy a new toilet that is taller, add hand rails to the sides for support of the heavy person too - it will help take some of the stress off from the toilet.

Buy toilet shims and shim the toilet. They are made of plastic, not wood. If that stops the problem, (YAY!!!!!) but if not,

Thisbe De Mona is right, you have a sub floor or maybe even joist problem. I would inspect from underneath before tearing out so that you know the full scope of the job.

Being realistic, repairing water damaged floor joists is a big undertaking, it’s probably something you should hire out so that the toilet is up and working again in a couple of days instead of weeks.

Hope that helps

😊

If your doing the cooking, maybe the'll change their eating habits and start to loose weight. Their just plopping down on it, instead. of sitting down. I don't know what to say about fixing the toilet. Call Homedepot or Lowe's plumbing department and see it they have something that could help you or go there.

We bought these, T-bumpers, easy to install, cheap and works well... saves on hinges too. https://www.amazon.com/Compac-Safe-T-Bumpers-Toilet-Seat-Stabilizers/dp/B000BI5UHO/ref=sr_1_fkmr1_4?s=hi&ie=UTF8&qid=1509294430&sr=1-4-fkmr1&keywords=toilet+seat+install+slide+prevention

Buy a standing open seat (strong) that can hover over a toilet

On a slab, Huh! I would try something like Rodena Josey or Dawn Blalock did to raise the toilet off the flange. You can also use a floor leveling cement to raise the floor even or slightly above the flange so the toilet sits on it and not the flange. I have used the plastic toilet shims and they tend to loosen or slip out.

If none of the fixes work, buy an over-the-toilet commode rated for the person's weight.

https://www.homedepot.com/p/Carex-Health-Brands-Deluxe-Folding-Commode-FGB34100-0000/206572520

In that case, remove toilet and check state of flooring underneath. If no tile is crumbling, put the toilet back and balance it with a shim or two. Probably just broken tile which you can fill in with grout & small piece of filler tile. Good luck!

Thanks to everyone for your suggestions!