The Loyal Sisterhood of the Fireside Girls have four known buildings, with the possibility of more.
Fireside Girl Lodge
One building is in Downtown Danville, and is their official lodge. Little is known about this building, apart that it is sparsely furnished, with logs as chairs. There is an emblem on top, and this building is old. ("Fireside Girl Jamboree") It also has a beehive. ("Bee Story") It has a recording studio that Candace used to record the audio version of the Fireside Girls Compendium Guide. ("Just Desserts") It has a trap door that leads to secret passage outside the lodge. ("Night of the Living Pharmacists")
Fireside Girls Clubhouse
They also have a clubhouse in the woods. This clubhouse appears to be secret, with both defensive procedures and a secret knock for access. It has basic amenities, including a usable sink, bean bag chairs, and supplies, including water balloons. ("Isabella and the Temple of Sap")
The third building is the Fireside Cupcake Factory, located on an island in the middle of the sea. They probably package the cupcakes here before selling them. ("Fireside Girl Jamboree")
The Fireside Girls have a bunker in a secret location where they keep the Fireside Girls Compendium Guide. This bunker has so far only been mentioned. ("Just Desserts")