I have concrete slab basement floor with 3" cast iron sewer pipe sitting about 3" below the surface of concrete. To access this pipe I have a hole about 6" wide around this pipe (See picture). So if I try to screw flange over it the screws would end up in this hole or two close to it to be reliable. enter image description here

I installed 3/4" Dricore panel subfloor and now plan to install some kind of flooring around 5/16" on top of it. Assuming that I put few tapcons to hold subfloor panel in place, would it be sufficient to attach flange with short 1" screws that would only embed in the subfloor panel?

1 Answer 1


As this subfloor is only small tiles of wood if someone were to fall ans grab the fixture it could easily fail, even id the screws hold.

I would like to see something stronger like chemical anchors through the Dricore into the slab. the install manual says it's preferred to fix walls through the dricore into the slab, so it should be acceptable for WC flanges too.

As this is potentially a wet area I would go with a stainless steel anchors.

  • So if I place 8 x 2.5" tapcons through the panel around flange it can still not sufficient if someone grabs the toilet?
    – Uncle Meat
    Commented Jan 5, 2022 at 3:11
  • I don't know how strong the dricore panels actually are, but seeing as dricore don't suggest fixing anything other than floor covering to it neither will I.
    – Jasen
    Commented Jan 5, 2022 at 3:24

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