When applying a rubber waterproofing like red gaurd or aquadefence. What kisnd of morter do you use modified or unmodified. I have read through each one amd it dosnet say anything about what morter to use when your ready to tile.


If you mean what mortar to use before applying waterproofer (e.g. Redgard), then use unmodified with an alkali-resistant cement board tape.

If you mean what kind of mortar to use after the application of waterproofer (i.e. to apply the tiles), then use whatever mortar is correct for the tile of your choice.

For instance, larger or natural tiles usually need a modified mortar, while smaller tiles can use unmodified just fine. The packages of mortar will describe their appropriate tile use.


I have used unmodified on a cement board just one time to show me that I needed to use modified after it set so fast that it turned to sand after it dried. Do not use unmodified over the joints before you apply the waterproofing.

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