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I'm installing the DWV plumbing in my new addition. I've located the toilet flange and have temporarily screwed it to the OSB subfloor using a couple of coated decking screws so I can continue with the pipe installs.

What kind of screw material is recommended for the permanent installation of the toilet flange? I'm thinking along the lines of:

  • Treated deck screws
  • Stainless steel screws
  • Galvanized steel screws
  • Plain ol' "wood" screws
  • Something else

Water should never touch these screws, so rusting out should never be an issue, however, theory & reality rarely match up and I'd think that most here have dealt with a leaking toilet at least once in their lives and have seen bolts & screws rust out. I'm trying to decide if that's enough of a concern to invest in a more expensive rust resistant/proof fastener or if I'm overthinking it.

I'm not particularly interested in size/length questions, as I already know that a #10 or #12 is the right size for my flange, and it's only going into 3/4" OSB, so it doesn't need to be any longer than 1".

FreeMan
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4 Answers4

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Stainless steel or brass/bronze.

We're talking a very minor incremental cost unless you patronize an utterly ridiculous hardware store.

"Should" and "real life" disagree regarding rusty toilet screws. Condensate, quite common in summer weather, if nothing else, will get them. Any leaks, or splashes/spills near the toilet outside, no matter how tiny, will as well. For the same reason, folks who have been down this road once tend to waterproof wooden flooring under a toilet, and the edges of the hole the flange is mounted in.

You might want to add some material (blocking) below the floor so you can use longer screws, particularly with an OSB floor. A bit of scrap lumber might make a world of difference.

Ecnerwal
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I would stay away from the coated deck screws. I had terrible results from using them on a deck no less. You say there will be no water contact, well stuff leaks so stay away from regular wood screws and even galvnized. I'm at the point where I use stainless steel for everything that's questionable.

JACK
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Treated deck screws Stainless steel screws Galvanized steel screws Plain ol' "wood" screws

Use Stainless steel and forget about the rest

Also the toilet flange and bolts should be s/s

There is noting more nightmare then finding the bolts the ring and the screws totally rusted

DIY75
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Always use stainless steel screws to secure a toilet flange. Anyone who put other type of screws in has no business building toilet flanges in the first place. If the toilet bolts break the flange and it must be replaced, the stainless steel screws won't ever rust so they can still be removed

user214193
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