A characteristic of Douglas's work is his attention to both external and internal detailing. Such detailing was not derived from any particular style and Douglas chose elements from whichever style suited his purpose for each specific project. His detailing applied particularly to his joinery, perhaps inspired by his experience in his father's workshop, and was applied both to wooden fittings and to the furniture he designed. A further Continental influence was his use of a Dutch gable. The most important and consistently used element in Douglas's vernacular buildings was his use of half-timbering, which was usually used for parts of the building. However, in the cases of Rowden Abbey and St Michael and All Angels Church, Altcar, the entire buildings were timber-framed.