Τhe techniques of building conservation were developed to deal with heritage structures: buildings that are considered to be important because of their history, their architecture, or both. The same techniques can be used for ordinary old buildings, even ones that have problematic histories and, by modern standards, poor designs. The Old-Law tenements of New York will be used as case studies: when new construction was ended in 1901, 80,000 such tenements housed over two million people. The thousands of these buildings that still have exist have been haphazardly upgraded but still provide needed apartments; but they are also cheaply-built and perhaps a century past their expected life-spans.