DON’T ask me why I got so excited when I walked into the apartment on Thursday, 27 January 2011 and found two guys at work on waterproofing the bathroom floor. Perhaps because the drama of the big events — the knocking down and building of walls — had been over for a while, and nothing more dramatic than the chases for the electrical wiring and the first plumbing work had happened since work on the apartment started again on 10 January?
Phillip Davids and Justin Fisher, who work for Seamless Waterproofing and Coatings, applied a product called “derbigum” to the concrete floor of the new bathroom. Derbigum is what people in the building industry call a “polymer-modified bitumen waterproofing material”. It is black and feels like a rubbery gum, and was melted with a blowtorch before it was pressed down onto the concrete floor and around the two water outlets in the floor. I noticed that about 80mm or so of the walls at floor level also received a coat.
Once the derbigum had dried, it was covered in a coat of bitumen paint, which made the floor surface look as if a thousand dusty shoes had stomped over it, and then the walls of the shower area were painted with a waterproofing membrane called Cemflex. The latter product was applied straight onto the cement walls, and gave the cement a kind of permanently wet look.
I also noticed that the Cemflex was painted over the derbigum right around the bathroom where the walls meet the floor, creating a kind of a Cemflex skirting board.
When all these waterproofing products had dried thoroughly, the bottom of the one bathroom wall that will remain untiled was finished off by continuing the CreteStone plaster over the derbigum-Cemflex “skirting board”, right down to floor level.
After all this waterproofing, the bathroom was ready to be tiled and the slatted-wood floor could be installed. Onwards!
— Sunday, 20 February 2011