The purpose of the master's thesis was to analyze whether and to what extent, the building plot factor and the size of the free (not built) land affected the price of a single-family house. The building plot factor was, for purposes of this thesis, defined as the ratio between the building part of the site and the total land belonging to a house. The main purpose was to define an objective value frame that would help the real estate appraiser to compare two single-family houses depending on their building plot factor. We analyzed sales with single-family houses in the Municipality of Ljubljana in between years 2007-2017. The analysis was made separately for free-standing and terraced houses. Adjustment coefficients were calculated according to the period of sale, the micro-location in Municipality of Ljubljana (quartered communities) and the type of terraced house (twin, end or intermediate terraced house). Calculation of adjustment coefficients was made upon reference (comparable) houses, selected using the restrictive conditions. On the basis of adjusted sample, analysis of the impact of the building plot factor and the size of the free (not built) land on the price of a single-family house was carried out. For free-standing single-family houses, we found that the median of the price per square meter was increasing up to 800 m2 of free (not built) land and was decreasing after exceeding 800 m2. The building plot factor relevantly impacted the price of a square meter in the case of free-standing single-family houses, the higher the building plot factor, the smaller the median of prices per square meter. The same analysis showed that the building plot factor impacted the price of terraced single-family houses to a smaller extent.