Remove flange to replace underlayment?

[wfon55]

I'm replacing the underlayment over the subfloor around the closet flange. The old underlayment was particle board or OSB, and over the years it acted like a sponge, absorbing water from leaks. It seems to have spared the plywood subfloor. I'm planning to put in a vinyl tile floor.

Two questions:

(1) Should I replace the underlayment with OSB, or should I be using plywood, or does it not matter?

The rest of the underlayment appears to be a mix of plywood and OSB/particle board, as can be seen in the attached photo.

(2) Should I remove the closet flange to install the underlayment?

The closet flange is in good shape and is soldered on to copper pipe (see photo). I have easy access to it from the basement. Or should I piece the underlayment together in sections with the flange in place? If I left the flange in place, I'd try to slide the vinyl tile under the gap between underlayment and the flange, which could be interesting, considering the adhesive on the back of the tile. If I should remove the flange, should I call in a pro? It is a 4" pipe that is in close proximity to plywood, but I think I might be able to remove it by heating the flange from above - however, my equipment consists of a small butane torch I've used for small plumbing projects, and I suspect it's way too small for the task. Removing the flange would require two visits - one to remove and one to replace. I'm sure I'd still be faced with sliding the vinyl tile under the flange, since soldering it would damage the vinyl if it were in place.

[jadnashua]

I think, since you appear to have easy access from below, I'd cut the riser, replace the subfloor, then use PVC, a no-hub connector, and a pvc flange with a SS ring on it to attach to the new finished floor. You may need to go to a plumbing store to get the proper no-hub, since copper OD is smaller than PVC, and, they'll likely have the pvc flange with SS ring. The big-box stores usually only carry them with a painted steel ring, which can rust to nothing if there are leaks. The no-hub connectors they typically carry are for pvc-pvc, so they have the same OD, you need one with different diameters on each end.

The hardest part of this is cutting the copper so it is straight across, then getting the burrs off since you probably don't want to buy a pipe cutter for that size.

The proper place for the flange is on top of the finished floor.

[gardner]

I am by no means a professional, but I have faced similar situations.

Is the flange the right height currently to accept the subfloor you want to install? If you do not need to raise or lower it to accomodate a different floor thickness, then I think you could cut two puzzle-pieces of new subfloor to fit under the flange as-is and screw them into the existing subfloor.

I would use exterior grade plywood rather than particle board as it will stand up to moisture better.

I would also make some blocks to fit around the riser from underneath and ensure the flange is secure to those blocks with stainless steel screws.

Ideally the flange should wind up on top of the finished floor, but if the flooring will be vinyl tile, then the thickness difference is minimal. I think your flange will wind up at a usable height if it starts flush to the subfloor and you tile around it with the vinyl.

Jim's plan is probably best and if you call in a plumber to help, that is what she would likely do.

[wfon55]

Many thanks for your guidance. I'll probably try to fit the subflooring together around the existing flange. There is enough clearance to slide the vinyl underneath it. If that proves unworkable, I'll follow Jim's suggestion.