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    By Dennis Collin

    Dormers are a common feature with some older buildings in the UK. A recent Cadline blog detailed here: which shows how to create a dormer roof at a main roof edge by splitting footprint sketch lines and the application of sloping arrows to further define the shape.

    Fig 1. The finished result

    Brow dormers can also be modelled within Revit although it requires performing several modelling tasks with some 'construction walls' to help define the dormer cutting shape on the appropriate roof face. Whilst I would not say it is an easy task. It is achievable by an intermediate level of Revit user who has an understanding of what Revit wants and with a little tweaking and patience we can achieve the desired results.

    Fig 2. Setting up a reference plane for the brow

    To start things off I model my main building and major roof slab as desired. To produce the brow dormer sketch  a named reference plane to control the start point of the roof. The roof iteself will be modelled with the Roof By Extrusion tool.

    Fig 3. Defining the brow profile

    One the main profile shape is drawn, we can draw some defining walls which will be used in defining the dormer cutting shape.

    We also need to join the brow roof to the main parent roof to define the back curve of the opening, using the join roof tool. I have also attached front wall to the roof for clarity.

    Fig 4. A Work in progress!

    Obviously the next step is to cut the dormer opening. The side walls can be deleted as they are not really needed apart from providing some extra edges to the dormer shape. If the walls were there we may have trouble correctly defining the desired shape as Revit needs intersecting faces and will not permit the drawing of lines for dormer openings!

    Fig 5. Cutting the Dormer Opening

    Finishing the sketch and cleaning up the view here is a view looking at the brow dormer from below.

    Fig 6. The Dormer from below/inside

    The Window for the dormer is likely to be specific to the type of brow, nevertheless I would still model the window as a standard component family as it will easier to categorise, adjust, group and edit than the more limited In-place family option. Since it is specific we won’t be needing parameters to flex the geometry.