Single pen architecture and double pen architecture are architectural styles for design of log, and sometimes stone or brick pioneer houses found in the United States. In double pen, two log pens (four walls of a log cabin) are built and those are joined by a roof over a breezeway in between.
An example is the William Boyd House.[1] A report about Williamson County, Tennessee historic resources states:
Double pen dogtrot design residences are also found in the county with the best examples displayed by the John Herbert House (WM-152) and Beasley-Parham House (WM-433). Both houses were built with two log pens joined by an open breezeway or dogtrot and each pen has an exterior chimney. Both residences had the breezeways enclosed with weatherboard siding by the end of the 19th century. The original form and plan of the double pen dogtrot style is evident in both residences. In addition to these log homes there are many other residences included in the nomination which have one or more log pens enclosed or enlarged by later frame additions.[1]:37