In October 2020, our tile contractor but in several hundred feet of porcelain tile on our west facing veranda. About six weeks ago the grout started developing efflorescence. The tile contractor says he does not understand why, and is only offering to wash the surface with vinegar to clean off the calcium deposits.

I had been concerned that perhaps he did not put a Waterproof barrier between the concrete (laid in July) and the thin set. Yesterday he showed me a picture of the barrier he used. It is DalSeal TS. My research indicates DALSEAL TS is meant for INTERIOR use, and that the product which should have been used is DALDECK.

My question: could the use of a barrier made for internal uses cause moisture seepage if used on the exterior?

These pictures were taken three days after me washing away the previous calcium deposits.