Which thinset for bonding straight to concrete slab?

Donnie D.

well ive done alot of tile work over the last 10 years..but now i have my own house and really getting crazy about everything being perfect..i recently put down 16x16 ceramic tile in my basment on the concrete slab..its a laundry room..it about 80 square..i used the cheap 6 dollar a bag un modified CustomBlend® Standard Thin-Set Mortar..i put my washer and dryer on top the the tile about 6 weeks ago..no problems at all..

but now i am doing my tv room right above the basement and is also a concrete slab..is has vinyl sheet flooring on it with adhesive under neath,which i will scrap clean as possible..now i dont see any cracks in the slab yet,but i havent scraped the whole floor yet..

its 200 square,the house was built in 1950's..

now i keep debating if i should use

--MegaFlex® Crack Prevention Mortar (which i cant find at a local home depot)

--FlexBond® Crack Prevention Mortar

--Porcelain Tile Fortified Thin-Set Mortar

..i will be using large tile 12x24's