Market dynamics are an authoritative factor in real estate valuation. Assessing and exploring market based adjustments is imperative for obtaining the value of an object. This analysis offers insights into market adjustments by evaluating 1,000 valuations of single family homes in Austria based on the cost approach. While the cost approach is mainly used in the German speaking area, it offers an attractive opportunity of investigating market adjustments emerging from the divergence between the costs of a building and the value obtained on the market. This is captured by the adjustment based on market evidence parameter. In order to reveal the main determinants of adjustments as well as market dynamics for the Austrian real estate market, 1,000 real estate valuations by court approved appraisers have been collected over three years (2008ñ2010) and statistically analyzed. We introduce semi-parameteric additive regression models in order to capture nonlinearities in adjustment factors. Furthermore the analysis features an assessment of geographical dependencies by regarding spatial interactions between the regions. Results show spatial effects between the regions as well as a significant impact of demographical aspects on market adjustments. Outcomes help understanding market determinants as well as assessing and obtaining market adjustments for future appraisals.