On Thu, 11 Oct 2007 13:41:43 -0700, wrote:

Okay, I know this is probably a stupid question with an obvious
answer, but...How do I tell if my concrete basement floor is level or
not? It's not so bad that it's obviously wavy, but I don't want to
plan on finishing the basement with an engineered wood floor only to
find out that it's slightly out of level. I've heard as little as 10
mm over a 3m length will cause problems, but I am not sure how to
detect this amount of dip or rise. Thanks for any help!

Level or flat?

For level, fill the room full of water and measure the depth at
different places.

For flat use a long straight edge that you have verified is straight
by putting it against something else that is flat.