Some professors a my institution are asking for "common" spaces in which post-docs are not allowed. Is this ok? I have been working as a postdoc for nearly a year. In recent months, the university is working to upgrade office and common spaces within my particular building. Some professors wanted a "Faculty Club" which is something like a common space for interaction between scientists to share ideas and discuss problems. However, in the last faculty meeting some professors stated that this should be a space "only" for them and postdocs would not be allowed there, not even to use the coffee maker.

Now I live in a country (Chile) where there is a social rising with people demanding for equality and to stop discrimination between different social classess. In this context, the universities have a role to be an example and to educate people according to the social demands. 

However, I see the same discrimination within the university, when you have professors that does not want to share spaces with postdocs like we were second class citizens. I understand that professors and postdocs have different needs in term of office spaces, but I don't think that in the middle of the 21st century you should start to ban people to use certain spaces just because they are "less" than you.

Is this common in academia?
You ask if this is common in academia. In all universities I've been in (only Europe), I've never seen something like this. Common rooms where usually for every employee of the respective department (administrative staff included). 

Solar Mike mentions in the comments "Professors have a need to discuss "privileged" information such as grades which postdocs may not have the right to, so separate spaces are a reasonable necessity - and not a social slur...". That professors need to discuss privileged information is true -- but I usually saw a simple solution for that: People were allowed to book rooms for meetings and then only invited people were allowed to enter. This also takes care of the fact that sometimes privileged information needs to be discussed only by some professors (not every professor who drops in), sometimes between professors and postdocs (or between postdocs or phd students). If  your professors' argument is also that they need to discuss privileged information, you might want to suggest this possibility.

However, I suggest you to choose your battles wisely. Academia is a very hierarchical world -- it can be dangerous to start a battle about minor issues (as long as you are not a tenured professors).  Especially if your faculty wants to have a faculty only room (i.e. they themselves are no advocates of "flat hierarchies"), it may be dangerous to suggest too many revolutionary battles. If equality is really so important for you, try to find a professor who advocates for you.

(Depending on how your institution is, you might also want to fight for a "non-professor only" room.)