Real estate appraisal in Germany is partly codified by law. The federal Baugesetzbuch (abbr. BauGB, "German statutory code on building and construction'") contains guidelines on governing authorities, defines the term market value and refers to continuative rules (chapter 3, articles 192 ff.). Each municipality (city or administrative district) must form a Gutachterausschuss (appraisal committee), consisting of a chairman and honorary members. The committee gathers information on all real estate deals (it is mandatory to send a copy of each notarial purchase contract to the Gutachterausschuss) and includes it in the Kaufpreissammlung (purchase price database). Most committees publish an official real estate market report every two years, in which besides other information on comparables the land value is determined. The committees also perform appraisals on behalf of public authorities.
If you're refinancing a conventional mortgage, a low appraisal can prevent you from doing so. The home needs to appraise at or above the amount you want to refinance for your loan to be approved. However, if your existing mortgage is an FHA mortgage, you can refinance without an appraisal through the FHA Streamline program – a great option for underwater homeowners.