The housing stock of England and Wales was constructed over several hundred years although the great majority of those houses were built since the middle of the nineteenth century. However, there are still many houses standing that pre-date this period. During this period, many housing architectural styles were introduced, and many of these lasted for considerable periods of time and produced buildings that are still in use today. Many different forms of construction and types of materials have also been used, many of which are still in use, while others which are no longer favoured. This chapter discusses the principles of house design and construction during the past 500 years or so and outlines a number of the more common defects that the houses can suffer. A more detailed discussion of the causes of the defects, their investigation and their impact on a building is set out in the chapters that follow. This chapter is divided into four sections: Section 1 is the Introduction; Section 2 covers the period up to the First World War (up to 1914); Section 3 covers the inter-war period between the First World War and the Second World War (1918-1939); and Section 4 covers the period from the end of the Second World War until approximately the end of the twentieth century (1945-1990). This division makes sense as the First World War is a watershed in terms of house construction. Before then, house building was essentially based on traditional construction methods and materials that had developed over hundreds of years. Housing since the end of the First World War (i.e. since 1918) saw modern construction methods and materials applied, first slowly and then at an increasing pace through the remainder of the twentieth century and into the twenty-first century. This was due to the increasing demands for: (1) new housing as the population increased; (2) better-quality housing as living standards rose; and (3) more environmentally efficient buildings as the effects of climate change became apparent. Industrial progress, increasing knowledge of how buildings perform and the development of new materials have also greatly influenced building design and construction in the past 100 years or so. In this chapter, vernacular buildings and Georgian and Regency housing are discussed in greater detail than housing during the Victorian and later periods. This is because the houses from the middle of the nineteenth century up to the present day make up the great majority of our current housing stock and the problems associated with their poor performance are really the main subject of this book.