A roof upstand is a raised element at an edge, opening or junction. It forms part of the connection between the roof surface and adjacent components. Dimensions and finishes follow the selected roof assembly and the purpose of the detail.
How this term relates to your project
Different materials may meet around a rooflight or against an existing wall. Ask how waterproofing, insulation and visible finishes connect. Review both a section and the appearance from the garden and upper windows. A low upstand in an inspiration image does not establish that the same detail suits your extension.
Include the rainwater route and maintenance access. The quotation should identify the elements supplied within the combined detail. This avoids uncertainty over whether the roofer, frame supplier or builder completes the remaining junction. Keep the agreed section with product information so the chosen arrangement remains understandable after finishing.