The roofs will be capped whether or not we build a second level on the garages because I'm not a fan of flat roofs. We're looking at about 9m length of wall to be built for each garage which would give us about 9sqm of space which isn't terribly efficient. It's a lot of wall compared to the space created.
If you're shopping around for homes one of the best ways to experience the floor plan of a home before you buy it is to walk through the developer's model homes before hand. One of the easiest mistakes is to get sold on the upgrades that a home stager and contractors have upsold the model on! Try and strip away the gorgeous finishes, the upgraded carpet, color coordinated wallpaper and drapery and focus on the layout and flow of the rooms. This will help you make an informed decision when choosing a floor plan.