Yes, the slope of the site can significantly impact construction costs. To ensure that a house on a hill such as this will be safe for the occupants and neighbors, it has to have a substantial foundation that is designed to survive earthquakes and small landslides. Retaining walls are another expense that most of these projects incur. This house sits on six concrete piers that extend 30' down into the ground.

The additional cost for this construction is usually factored into the price of hillside land, which is generally cheaper than flatter sites. The difference in cost varies based upon a variety of circumstances, and some of the uncertainty that hillside construction produces also contributes to the lower-cost of hillside land.

When looking to purchase sloping land, you need to be careful to make sure that you will be able to build on it and to consider the additional construction costs you will incur. It is typically a good idea to have a geo-tech report done if one has not already been completed.