Most atlases are intended to be used for a number of years. In order to take into account any changes in the real estate patterns of the ward during this period, most atlases are intended to be updated by the use of paste-ins of changes. While the researcher often may find this beneficial, just as often he finds it a nuisance. Moreover since atlases are designed for long-term use, it is very rare that the researcher will find atlases for consecutive years for the same ward. Even by using those published by a number of publishers, he is liable to find that he can only approximately date a house at best within a five or ten year span.
Some atlases raise more specific problems.
The 1862 Smedley for example, does not indicate specific properties for city blocks and does not code buildings. Since it is the only atlas between the Hexamer and Locher and those published in the early seventies, the researcher begins with an automatic handicap. However the Smedley does have the redeeming feature of indicating specific buildings in rural areas. The fundamental step in dating a house is a search of the chain of title, without which it is usually impossible to identify the exact year of construction, especially of older buildings. Only when equipped with the list of successive owners of the property, provided by a title search, is the researcher able to use efficiently other sources to determine precisely the year of construction .