A plattegrond is a plan or map. You can often find plattegronden of a house or larger areas in image collections of archives or the Rijksdienst voor het Cultureel Erfgoed (Culturel Heritage Service).
I am currently doing a House History module at the university of Dundee, for which I am studying the history of a house in Bredevoort. As part of the research I found a plattegrond of the house in the collection of the Rijksdienst voor het Cultureel Erfgoed. This plan showed the situation in 1961, with the weaving chamber and indoor stables still intact. Subsequent research in cadastral records and notarial records showed several weavers lived in the house in the nineteenth century. This plan shows their working conditions, in a room of 1.87 x2.48 meters (6’x8′) with one tiny window; just large enough to fit a loom.