Can Schluter ALL-SET™ and Schluter FAST-SET™ modified thin-set mortars be used to set tile over Schluter boards and membranes?

Yes. All Schluter Systems’ thin-set mortars, including the ALL-SET™ and FAST-SET™ modified varieties can be used to set tile over DITRA, DITRA-HEAT, KERDI, KERDI-BOARD, etc. Additionally, all Schluter thin-sets are engineered to perform predictably, even when sandwiched between impervious or non- absorptive surfaces (i.e. porcelain tiles and non-absorptive substrates).