Flange install advice for 4"stub with insulated sleeve

[Pghgreg]

Hello,

I am preparing to tile and install a flange on our new construction basement bathroom. The toilet stub is 4" and was finished to top of slab with a plastic cap a few years ago. I've finished instilling ditra heat mat and am ready to tile. Upon removing the cap it became clear that the there is a sleeve around the stub with an inch of foam insulation (the insulation starts about 6" down leaving an sizable air pocket/gap). A standard flange slides into the stub freely, but the anchor points for the flange fall on the edge of the gap formed by the expansion sleeve. The lack of structure around the stub is disconcerting, but it seems very secure.

Assuming I should not fill this expansion gap (?) with concrete, what is best practice in this scenario? Tile to the sleeve and use a repair flange with extended anchor points? Will that be secure enough so as not to stress the PVC and make for an install that stands the test of time?

All advice appreciated!

 

[Reach4]

That foam is just temporary to keep out the concrete during the concrete pour.

http://www.oatey.com/doc/Foam_Closet_Spacer.pdf is one brand.

I think I read that some hit the foam with a torch to make it go away instead of digging it out.

The security will be from the bolts that you bolt to the floor. You want a flange with a metal ring rather than a plastic ring.

 

[Sponsor]

 

[Cacher_Chick]

You can fill the gap with mortar if you need to in order to have a viable location for screws or anchors.

 

[hj]

I just slide the flange on and mount the toilet if it is a concrete slab.