Karen asks: We are considering buying a property that’s labeled as “gently rolling”. Do we need a builder to look at it in order to tell us if a walk-out basement is possible? How much slope is required?
Steve Bliss, of BuildingAdvisor.com, responds: Assuming an 8 ft. foundation wall, and assuming your foundation projects one foot above grade at the front of the house, you need approximately a 7 ft. change in elevation from the front of the house to the back for a walkout.
Much more slope than that would be expensive to build on and might require expensive retaining walls. A little less slope (4-6 ft.) is fine as the house can be raised in front, or the grades adjusted a bit in the finished grading. In general, walk-outs are a little more expensive to build in cold climates as deep footings are required on the walk-out section of the basement.
As to whether you have enough slope at your desired house site, you might want to have a builder or house designer take a look. There are often constraints as to exactly where on the lot you can build a house. These include setbacks, septic location, drainage issues, road access, etc. On smaller lots, there are only one or two practical places to site a house, so you would need establish at least a preliminary house site before addressing the walk-out issue.
See also Building On A Slope