This is a Bachelor’s degree project withthe aim of investigating how to preventwarranty errors in apartment buildings.Our goal has been to compile the mostcommon warranty errors and the reasonbehind them.To achieve this goal, we have studiedthe warranty protocols from fiveprojects. We also performed interviewswith people who work in house productionand people who work with warranties. Thepurpose of the interviews was to findout the underlying causes of warrantyerrors and what one could do to preventthose.Cracks in walls and ceilings were themost frequent remarks on the warrantyprotocols. Remarks on the floors,windows and doors were also common, butnot to the same extent. This wasconfirmed both by the studies of thewarranty protocols and from theinterviews. The reasons behind thesewarranty errors were based on manydifferent things including deficienciesin the choice of technical solutions andmaterials.The results from the interviews showedthat if the company is to preventwarranty errors they must firstly raiseawareness about warranty errors.Secondly, they should highlight what themost common and costly warranty errorsare. In order to do this they shouldstart gathering statistics from thewarranty protocols.An evaluation of each project should bedone when the warranty expires. Thewarranty errors that occurred and theunderlying causes must be analysed. Theevaluation of each projekt must be usedto prevent future warranty errors.Experience feedback is very important ifwarranty errors are to be prevented.