Thanks to the forum owner and administrator for a means to ask questions! This is great for a plumbing novice.

This is more of a carpentry issue than plumbing but I'm sure many of you have already solved this.

I've gutted my 1955 bathroom, including the tile floor and am replacing the subfloor (the subfloor was poured concrete and mud between and over the floor joists with tile on top). The toilet flange and waste line are all cast iron. My flange has two simple notches for the toilet bolts to hook onto, otherwise it's just a round disc. Hard for this untrained eye to tell just how it's attached. The flange appears to be in good shape.

Question.. Can I cut a hole in the plywood subfloor, just wider than the flange and drop the plywood over the flange and waste line, or should I cut a seam down the centerline of where the toilet will sit and attempt to get a close fit to the flange collar/waste line? The distance from the flange collar to the outside of the flange is 5/8".

Also, the waste line and flange were pretty well encased by the concrete subfloor. The wasteline just past the 90 elbow is supported by a single piece of steel strapping. Now that the concrete is gone, do I need to add any additional support to the flange and waste line? Got to believe this is pretty heavy pipe hanging out there!

And, sorry to be so full of questions, but how high above final floor should the top of the toilet flange sit. I don't have the original instructions for my 20 year old American Standard toilet but instructions on-line for current toilets said about 5/8". I may end up being more like 3/8".. is this OK?

Thanks for your help!

Beltsville, Md.