The total size of a commercial building has been trending up. The average size was around 16,300 square feet in the 1990s compared to 19,000 in the 2000s. EIA research shows size still rising as recently as 2012. With larger buildings representing nearly 20% of commercial stock, odds are growing that any one business will be in a bigger space. While a newer building means better construction techniques and more durable materials, it also means costs associated with square footage.