On average, stone foundations cost between $12 and $35 per square foot. This includes material and labor costs. For example: For 800 square feet, the cost can range from $9,600 to $28,000. Stone foundations are environmentally friendly as they use natural materials that blend seamlessly with the surroundings. Specializing in racking solutions for ground mount solar array structures, SFUSA can make your. . The total cost of installing a ballast foundation usually ranges from $0. This method is often used in areas with rocky or compacted soil where digging is challenging.