How to Build Tile Countertop Substrate PT I

[@vivivs2774]

Tile levelers for cement board! What a cool tool, thank you.

[@philliphanford2792]

In my situation I do not know if my 3/4" plywood is exterior or not. Do you rely on the polymer modified thinset to protect the plywood from moisture or paint the plywood with latex or preservative?

[@mralexdenny]

No need to paint- or seal - best to have at least 1/4" thick layer of cement /hardi over the plywood as the plywood substrate moves indifferently to tile -- 3/4" is more than adequate-- overlay all and any seams-- don't want cracking -- or add an "Anti Fracture" cloth membrane if not using cement board as well--

[@philliphanford2792]

@@mralexdenny I plan to use 1/4" cement board but in framing construction I never allow direct contact with cement. Cement draws moisture, causes rot, the saying goes. So maybe the polymers will form a layer inbetween.

[@mralexdenny]

@@philliphanford2792 the polymer modified Motor mix is designed to adhere directly to plywood--safe to use--

[@philliphanford2792]

@@mralexdenny From my experience with concrete and wood I think I will use Schluter Ditra instead since I don't know how well the polymers make a moisture barrier. Yes it adheres to plywood fine.

[@mralexdenny]

@@philliphanford2792 Good plan-- Ditra -mat is bullet proof-- still need the "Polymer mortor to adhere to the plywood-- then non-polimer to adhere tile--

[@slayerspam]

A non polymer mortar between porcelain and hardie?? That polymer is intended to extend thinset open time to allow greater impregnation/growth of the crystals into the hard to penetrate surface of dense tile like porcelain. I believe that the non polymer should be used underneath the backer since there is absolutely no need for the mortar's adhesive qualities given that screws are to be used for that purpose instead. Plz someone tell me if I'm totally off because I',m about to do kitchen counters. What is the Polymer even for if what I described above isn't correct?

[@jesterraj]

why didnt you just tile over the plywood?

[@mralexdenny]

Hi Raj, Good Question--:--the plywood is not stable enough with changing humidity therefore preventing cracking in the tile. Dissimilar materials expand and contract at dissimilar rates.

[@jesterraj]

@@mralexdenny ok thx..but it can work leyts say u live in a dry area ...

[@mralexdenny]

@@jesterraj Still better to fasten off minimum 1/4" or 5mm thick cement board or some kind of a "Anti Fracture" fabric membrane -- and two layers of ply-

[@jesterraj]

@@mralexdenny ok is for a small counter to for a kitchen sink area

[@mralexdenny]

Sounds good--- use silicone on the edges, and use a "Pre Sealed" grout , main concern is to prevent water form getting on to any wood. you can also use a "Shlutter" membrane over the plywood, there is a thick version or a thin version "anti fracture" membrane as well as a 12mm foam, check out some Schlutter videos. Where are you located?