Lap marks refer to differences in the sheen and colour of paint. Lap marks usually appear as higher gloss or denser colour than the rest of the wall.
Causes:
Lap marks occur when dry and wet layers overlap during the painting process. Lap marks are more likely to occur if the paint is applied in direct sunlight or in a warm room, and they can also happen if the painting surface is too porous.
Solution:
As always, it’s important to use high quality paint and tools for your paint job. Ensure to always maintain a “wet edge” to your painting area and use a wet to dry technique. Painting in small sections will make this easier. Additionally, avoid painting on a very sunny or overly windy day, as this will make your paint dry faster. If your painting surface is porous, begin with a primer and keep in mind that you may require two coats of paint.