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JP6044 01-27-2011 10:03 AM

Does the plywood have to come out? AGH!
Hello all... got some help here a few days ago, so I thought I'd give it another shot with my problem...

Working in an upstairs bathroom - removed the vanity to find no tile was under it, so I decided to rip it all out and put something a little nicer down. Tile was apparently fixed directly to the plywood, which as I understand is not something a novice should try to replicate. So, out I went and got wonderboard - cement backerboard. Before installing it, I added several screws to the plywood to ensure that it's stable and not moving at all.

I then cut and laid out the cement backerboard, but was quite unhappy with it. It felt like piece 1 was slightly lower than piece 2. A couple places popped/cracked, as if there was something like a pebble on the floor beneath the sheet (which there's not). So, I took it all back out, and am thinking that Durock would be better.

But, should I consider removing the plywood altogether? It appears that there is a very small "dip" where the old vanity was. Maybe 1/8" or less, which I assumed I could fill in (and level) with thinset mortar before proceeding. I REALLY want to avoid taking out the bathtub, which I assume I'll have to do if I replace the plywood floor.

So, any thoughts? Should a novice like myself remove the plywood and start fresh, or do you think the durlock/mortar approach will suffice?

FYI, this is a fairly small bathroom - tileable floor space is about 5 X 7.

Any thoughts/guidance would be appreciated!

Jim F 01-30-2011 03:15 PM

You have to level the floor under the cement board, whichever you use or that popping will continue and will result in cracks in the grout and tile of your new floor. They sell levelling compounds for this but morter might serve as well. Dome like to use Ditra systems as well.

Hopefully some of the floor experts will pitch in to help now that I've bumped your thread.

oh'mike 01-30-2011 04:15 PM

All backer boards need to be set into a bed of thinset before it is screwed or nailed.

This will take care of the 'voids' that would allow the backer to 'snap-crackle and pop'

If the floor is still not flat enough after the backer is down ---use a self leveling compound like

Jiffset and Linewebers latex to float out the low spots-----mix it thin--work fast --Mike--

JP6044 01-31-2011 08:10 AM

Thanks guys... much appreciated!

jimg3958 01-31-2011 11:07 AM

Run screws down the joists on the plywood. The popping is your sub floor mooving up and down on a nail ever so little. Then get
1/4 inch permabase or durorock and over the plywood. Screw it down. One screw every
8 inches.
If the floor is to unlevel for you, go to lowes and ger a quart of level primer and paint the durorock with it. Let it dry for about 1 hour. Then get levelquick or a self leveling product in the tile section of the store. Plug any areas you don't want this product to go. (Silicone around the toilet). Then mix the product with 6 quarts of water and poor ikt over the floor very thin. Move fat with the mixing and pooring over the last mix. It will flow together better. Do the whole floor and let it dry overnight.
Then scrape the air bubbles off the top and your floor is level and flat.
Good luck

Jackofall1 01-31-2011 11:36 AM


Originally Posted by jimg3958 (Post 581734)
(Silicone around the toilet)

I would remove the toilet if you haven't already, sealing the toilet to the floor could be a problem if it ever leaks, you won't find out until the water is dripping from the ceiling below, and by then there could be a whole lot more damage.


jimg3958 01-31-2011 12:17 PM

left something out
I just assumed you had the room torn totally out. Ya, I meant seal aroun the flange. Bo don't cement the backer board down. The thin set won't adhere to the ply wood and over time you will here it crunching under the tile, been doing this for a long time. The manufacture wants you to buy more product. If you screw the durorock down it will be solid to the sub floor, then when the leveler goes in it will be level. Then use the expencive 28.00 bag of thin set to stick the tile with. It makes a diference in how long the job lasts. Just use common sence when installing everything and you will do fine.

jimg3958 01-31-2011 12:20 PM

No the plywood is fine unless its a mess.

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