Wall Structure (from surface to base):
Latex paint > Undercoat > Moisture barrier primer > Putty > Cement plaster > Concrete/Brick
Scraping Process:
Wet the wall with lime water or clean water, then use a scraper to remove old latex paint and any loose undercoat from the wall.
Apply an oil-based moisture barrier primer.
Apply plaster.
Sand and clean the plaster.
How deep should the scraping go?
During the scraping process, the worker should scrape until they reach a solid base. In most cases, if the foundational layer of the wall is intact, they will only need to remove the old paint and any loose undercoat. Sometimes, if the undercoat is especially robust, it won't all be scraped off.
Scraping ensures the durability of the new paint but can be more expensive. If the plastering work on a new property is of good quality, there might be no need to scrape at all. The worker can simply sand the wall lightly and then directly apply latex paint.
If you have any questions about the construction process, please feel free to contact our renovation consultants.