Yes, we can make additions to a prefab building after it has been installed. If you know when you purchase your carport or garage that you will want these add on features later, please talk to the customer service representative to learn of the additional cost. A service charge will be charged to your balance for the return trip, and we will only install CarportUS.com products. Many times it is less expensive in the long run to choose a carport, garage, or combo unit that is equipped with everything you need initially. Our customer service representatives will help you keep your hard earned money by offering helpful tips for upgrading your custom carport or metal building.