By using Efflock, a secondary membrane to control efflorescence is not required. There are however, builders, architects and engineers who insist on including a secondary membrane as they like to 'cover all bases'. I can understand that; as builder myself, I like to include a few insurances in my work to avoid getting that phone call nobody wants. A secondary membrane remains good building practice, so long as excessive moisture is not sandwiched and trapped in between layers in the process.
I've also had situations myself in remedial work, where we opted to screed first, then apply a membrane and direct stick the tiles to the membrane. This approach also works well, and helps if there are finished height constraints with internal floor levels etc. Bonding the screed wet on wet directly to the concrete substrate means you can feather a tile bed out to 0mm to keep the finished floor level as low as possible, and this was an approach we took on a job back in 2010.
Above: Remedial work to a balcony. Waiting for tile screed to dry out sufficiently before a membrane could be applied.
The frustration of rain!!!
The stress and annoyance associated with both of the scenarios above, is that you can be helplessly at the mercy of the weather. It only needs to rain for an hour and the tile screed is completely saturated! It can take another 10 days of good weather to dry out enough before a membrane can be considered and applied. Sometimes waiting for that good fortune in the weather could take weeks or even months! That can mean huge delays and inconvenience for the builder and the customer.
Efflock is proving very useful to a number of our customers for exactly this reason. The permeable yet hydrophobic effect of a tile screed containing Efflock means that a tile bed can expel moisture from the hydration process, whilst repelling any rain that comes along in the mean time. A screed containing Efflock is able to dry out in a matter of hours, meaning progress can continue.