A way you can fix this is, when an employee gets bigger than say the doorway or a certain height, she can no longer come inside the building and has to stay outside. If you want her to do work, you then have to order special equipment just for her. Example: Outdoor treadmill/weight rack. Outdoor cash register. Or something.
Only other fix I can think of is, when an employee starts to surpass the roof, just have the roof removed the next day. Let them gals grow taller and taller!