View Full Version : Nowhere to fasten my closet flange...Help!

06-20-2011, 06:24 AM
When putting in the new subfloor we left the old cast iron pipe/bell/flange in place (Cutting holes in the floor to work around the pipe). After cutting this out due to holes in the old pipe, the opening left is about 6 1/4 inches. I'm having a hard time finding a flange that will be able to span this are in order to grab something once I put my tile down. I know that I need to put the flange on the finished floor. My questions are:

1. Am I okay if I can find a flange extension to add another inch or so, in order to fasten to subfloor? - suggestions welcome

2. would it be a good idea to attach another piece of plywood on the underside subfloor from the basement and then holesaw through that the proper size for my flange to attach to?



06-20-2011, 07:33 AM
If you have a cast iron flange with cast iron pipe you may not have to fasten it to the floor. The question then becomes how much below the finish floor will the flange be? A picture would be great.


06-20-2011, 09:19 AM

The cast iron pipe and flange are removed. I cut it in the basement, about 2 ft. from the stack. I'm running new PVC all the way up to the flange. What I want to know is, I have a 6 1/4 wide hole in the floor now - once I put my tile down and I fasten the flange to the floor i want one that is wide enough to screw into the subfloor. Any advice? I will post pics once I get home.

06-20-2011, 09:29 AM
There is no such animal. If it were any wider it would NOT fit under the toilet. In my opinion, your first mistake was removing the cast iron. THe second was NOT removing the flange before cutting the hole. Now, you have to figure out HOW to make the hole smaller so the flange WILL fasten to the floor.

06-20-2011, 09:47 AM
HJ, the opening is between 6 and 6 1/4 in some spots...not a perfect circle. I see @ HD they sell a 7" extension flange ring. I believe that this would sit on the outer part of this circle and work for me. It's the Souix Chief ABS 7" Flange extension. Any thoughts. My other option I'm thinking of is, fasting a piece of plywood to the floor through the basement and then re drilling out a proper sized hole.

06-20-2011, 11:39 AM
Hi Matt...

Your thought of fastening a piece of plywood from underneath is perfect here! Just make sure that it is a big patch that goes well beyond the hole in all directions and you not only secure a piece of plywood underneath, but you also fill the hole with plywood on the top side to bring the patch flush with the new finished floor and THEN drill through for your pipe being sure to leave plenty of meat to screw the flange, right?!?! :)

Use screws that are treated to resist corrosion, and for the best job see if you can find an ABS closet flange with a SS ring...lasts longest!

Good luck!

06-20-2011, 11:44 AM
Assuming you have access from below still, cut a nice piece of 3/4" ply to fit between the joists, cut a nice round hole in it to fit around the pipe while leaving room to slide the flange on, and screw and glue it to the bottom of the subflooring. You may need longer screws to get to it when installing the flange, but that will work. To keep the end of the screws from giving you grief on the top of the floor, drill through holes in the top subflooring, and screw from the top. The glue will hold it all together once it sets, the screws will act like the clamps until that happens. Get good coverage with the glue and don't skimp on the screws. Make them long enough to go through the new piece about 1/4" or so so the whole shank is holding, rather than just the tapered tip.

06-20-2011, 12:25 PM

Another vote for cut out the subfloor and patch it. Cut it so the edges meet 1/2 way over the existing joists. Add 2x blocking between the joists for the other set of edges. Lay a bead of construction adhesive on the joists and blocking, lay your patch and drive screws every 6 inches.