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Unread 04-17-2021, 07:26 AM   #2
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Join Date: May 2018
Location: San Diego, California
Posts: 102
Hi Cherie, I'm not a pro but can echo the answers I hear on these forums. You need to make sure your deflection rating is strong enough for the tile you're using. Go here and plug in your joist height, span, etc:

You need a rating of L/360 for ceramic tile.

Once you've verified that, look at the condition of the wood, and look for any gashes/holes/etc. If you have any really bad spots you may need to pull that piece up.

Next, check for flatness. Your subfloor only had to be level, not flat. The larger the tile, the more this matters. I think the rule of thumb is something like no more than 1/8" difference over 10', but someone will correct me if I'm wrong. You can use SLC for leveling, but not all of them work on wood, and done of them require it to be applied very thick to get strength.

If you don't want the thickness, you can remove the subfloor and do things like plane the joists to get where you need to be.

Once that you're as flat as needed, you can do hardibacker, ditra, or numerous other products depending on your comfort level and budget. Uncoupling membranes like ditra are the easiest since they cut with a razor and are light, but they're also not cheap.
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