This paper describes some of the characteristics of the constraints, caused by the architects' decisions, that affect the choice of technical solutions in timber engineering and especially in design of multistorey houses. The constraints serve as requirements on design automation algorithms that are supposed to select the most cost-effective technical solution and design the selected solution within a given set of architectural constraints. The results presented in this paper are a very condensed version of the results from interviews with architects involved in multistorey timber residential house projects in Sweden