Zoning Map- Trying to understand...

[Joe Edwards-Hoff]

I live in Kittitas County of Washington state. I have a map for zoning, but I am having troubles understand 1) if it is current (it is on the county website) and 2) what exactly it means. There are low and medium density properties all around, but I can't find anything stating exactly, how much I can build or add to a lot of X size. I am just trying to look into, if I got a house on a certain lot, could I ever add to it, or build another unit.

http://www.ci.ellensburg.wa.us/index.aspx?nid=107

Map-
http://www.ci.ellensburg.wa.us/DocumentView.aspx?DID=312