Construction methods vary, and will change the performance that is ultimately achieved. Performance is the key point with regard to speciﬁcation of elements and materials. How can we establish the level of performance to be expected, that will improve a building’s life values? Several measures give the speciﬁer some conﬁdence as to the eventual outcome;
however, these can be signiﬁcantly altered by issues outside the designer’s control, and this will have a central role in determining the life of any element.