One of the most rewarding home improvements I made to my house was to build a garage addition. For years I contemplated building a garage addition while I scraped the ice and snow from my cars and waited for them to warm up during the winter months. About 5 years ago I finally made the decision to build a garage onto my home.The first big decision I had to make after deciding to build the garage addition was to determine how large to make it. I wanted a large enough garage to fit two cars comfo.