It is probably easier to not use GDL for what you want. Instead, bring in your site plan, ideally with each building fill or outline as a continuous-edged outline. Then just use the slab tool and magic wand each outline or fill into a mass.
Karl
AC 28 USA and earlier • macOS Sequoia 15.3, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB
One of the forum moderators