Hello,
I am working on a bathroom renovation in a single-story 1950s house with a slab-on-grade foundation.
In the bathroom, there were tiles on 5 cm concrete, then under this was asphalt coated on the concrete. This coated layer was about 10 cm thick and is now removed; underneath lies the foundation slab (15 cm of very hard concrete with 16-32).
My question is about the bottom concrete; it is also coated with some kind of paint/layer. Something that is black-brown and very thin. It appears to be over the entire slab and not just in the bathroom (as the tar was).
Is this an alternative to sill paper or some kind of old-fashioned primer to make both layers adhere to each other?
And does this coating need to be removed before pouring new overlay concrete? Or is it enough to scrape clean on the "peaks" and use primer?
