Facts
In 2007, [Y. AG] (Plaintiff, Appellant and Respondent) carried out extensive renovation work on its property in [Q.] . By letter dated 18 April 2008, it notified A. and B. [X.] (Defendants, Appellants and Respondents) of a net rent increase of CHF 334.-- for their 4-room apartment. The Defendants contested the increase with the Conciliation Authority, whereupon the Plaintiff filed a lawsuit with the District Court of Liestal. The District Court, the Cantonal Court of Basel-Landschaft and ultimately the Federal Supreme Court had to decide on the permissible rent increase.Considerations
The Federal Supreme Court concluded that the work carried out constituted a comprehensive renovation within the meaning of Art. 14 para. 1 sentence 2 RRBPO. Therefore, 50-70% of the investment costs were to be classified as value-enhancing and could be passed on to the rent. However, the lower court had wrongly set the proportion of value-enhancing investments at 45%, instead…