The straight entry is a one storey design with a full basement, providing ground level access at the front with the main living areas all on one floor. Generally this type of design is most suited for a rear sloping lot, though it is often built on level lots to take advantage of the extra floor area that a basement provides. The basement level in either case, allows for future expansion at a minimum of cost for such things as recreation, bedrooms, workshop and hobby rooms.
If contemplating an in-ground basement, be sure to check the depth of your sewer services before purchasing plans. Your basement floor should be above these services to provide for proper drainage.