You would be better served with some thing like AutoCAD Lite. Google Sketchup maybe. Pencil and paper have real merit too. Draw a box on a sheet of paper for each room and put down a mark that means receptacle, door, etc. Put the sheets in a folder and quickly move on.
Making drawings of a building interior seems far removed from managing safety and health in a school, and perhaps not time well spent, even if you were already skilled at drawing such things. I would recommend prioritizing meeting students and teachers, administrators and custodians, to learn what health and safety needs are not as well served as they could be.
What benefit to health and safety could there be from documenting where a tree is planted? You could just look at it and see. I can understand documenting things like cable raceways and the contents of data closets, because they are hidden. This sort of work typically falls to facility managers, or in a factory, to some industrial engineer.
If you can't draw a straight line between some health and safety need and a map that shows doorways, trees, and receptacles then the mapping is not time well spent.
It will be time consuming learning to use Dia for such an involved project. There is very little tutorial help. The usual way we learn Dia is by messing around a lot, and asking specific questions about Dia functions in this forum.
Admittedly, your title may be less accurate than it could be. Perhaps your work really IS facilities and grounds management. You should still consider a 2D CAD program instead of Dia. DIA IS NOT GOOD AT THIS KIND OF WORK.
Steve Lott mentioned Inkscape which is an excellent program. I would not like it for facility drawings. You could do it, but will be a long process.
I swear to you hand sketching is very useful. It might buy you some time to evaluate and learn a good drawing or CAD program. Don't try to measure and record exact locations, just get close so when you stand in the room, hallway, or yard, with the paper representation, it makes sense.
