I'm going to lay carpet on a 17 years old screed. The floor is very level, and I have carefully removed any minor protrusions (flecks of putty, etc.). Now I wanted to start laying the carpet (without gluing it all over the surface) and at the last minute I discovered a single, lone small hole in the screed. It is about 8 mm in diameter and about 8 mm deep (the screed itself is 6 cm thick). It was a rusty brown color on the surface. After cleaning with a squeegee, only the edges remain slightly brown.
Do I have to cover this area, or can I just put the carpet on top?
I would cover the hole (with mortar, plaster, or whatever wood is there). With a diameter like that, you might still notice it. Or a woman in high heels could, depending on what's installed there, poke it through and then you'd have a hole in what's there.