Hi,

I have engineered hardwood floor glue down to concrete in the basement.

Normally, what should the moisture content of the floor be to avoid issues like delamination, cupping, etc?

If the concrete has high moisture that caused the engineered flooring to have 25-30+ moisture content, is that an issue?

Well first off adhering to a basement slab is just asking for trouble unless you had some bullet proof epoxy coating done on it. No one warranty's in a basement unless you had extensive moisture testing done and documented. Plus an adhesive/moisture system installed on it. Even then the high mver's can over come many of these systems if there is not a 2 part epoxy system put down first.

Besides all that, you may actually have real water entering the slab. A wood plank that exhibits 20 to 20% moisture content is sopping wet.