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dankreboot 06-04-2008 12:51 PM

Thinset under concrete backer board?
Hello All,

I'm going to be installing tile on my kitchen floor which right now has plywood. I'm going to be installing a 1/4" backer board over the plywood so I can tile. My question is should I set it with thinset and screws or is screwing it in enough? All suggestions and opinions would be appreciated.


Bud Cline 06-04-2008 01:24 PM

Suggestions and opinios don't count. READ THE INSTRUCTIONS!

ALL backerboard makers want their product set into a fresh bed of thinset, in some cases unmodified thinset.:)


Steven62 06-04-2008 03:43 PM

TCNA handbook is a good idea too, if you have never read one! Lots of sound info.:thumbsup:

Bill_Vincent 06-04-2008 07:08 PM

What Bud said. Use the thinset.

JAVAMAN 06-05-2008 11:25 AM

I Used To Lay Tile And When Ever We Used Cement Board We Always Put Ir Down With Thinset And A Nail Gun

Termite 06-05-2008 02:37 PM

Also mud and tape the seams with fiberglass mesh tape and thinset.

JAVAMAN 06-05-2008 02:45 PM

Oh Yeah I Forgot About The Tape And The Seams. That Helps To Prevent Cracks Ans Other Things Over The Years

JazMan 06-05-2008 04:27 PM

Just so to not confuse others, we do NOT "mud" and tape any seams with any CBU. The proper term for the product used is "thinset". Mud is something completely different in the tile business.

I only bring this up because there are many hacks out there that use the term "Mud" when they only spread thinset to set tiles. :furious:They are trying to deceive others to make them think they are actually doing a "real mud job" when they are not.:no:


angus242 06-05-2008 05:04 PM

Since this has gotten technical.....
Make sure you use an alkaline resistant tape over the backer seams. Also, make sure you stagger the seams for each row. You then use thinset over the tape and screw/nail holes.

I think between all 6 of us, we covered everything now! :thumbup:

Bill_Vincent 06-05-2008 05:23 PM

Alkali resistant alloy screws or nails. ;)

angus242 06-05-2008 05:45 PM


After all of this I hope Dank even reads this :whistling2:

JazMan 06-05-2008 06:21 PM

Hey....installing tiles correctly can be technical:thumbsup:

I'm sure it doesn't hurt, but thinset over the fasteners is neither necessary nor recommended.:wink:


angus242 06-05-2008 06:57 PM


Originally Posted by JazMan (Post 128171)
thinset over the fasteners is neither necessary nor recommended.

OK, but as a precaution. What if a fastener blasts through the bottom of the CBU or if you get too close to the edge and crack the CBU?
Besides, doing that helps keep dust and debris out of the counter-sunk screw holes. I hate dusty CBU when trying to thinset!

So point taken but I don't see how it can hurt. :)

JAVAMAN 06-06-2008 03:22 PM

Yes Thinset Is Used. Oh I;m So Sorry The Word Mud Came Up Thinset All The Way.

Thinset/mud Most People Know What Ya Mean

Bill_Vincent 06-06-2008 03:27 PM

Javaman-- keep in mind-- this is a DIY forum. Everyone who comes in here WON'T necessarily know what's meant.

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