Building a Manual Dormer in Home Designer Pro

Reference Number: KB-00396
Last Modified: September 6, 2019

The information in this article applies to:

Home Designer Professional


How do I create a manual dormer in Home Designer Pro?

Camera view of house with two dormers


There are several methods for creating dormers in Home Designer Pro, including using the Auto Dormer or Auto Floating Dormers tools, automatic roof generation, and manual roof tools. In this article, the manual method for creating a dormer will be used in a basic 40' x 30' rectangular structure, with a 10 in 12 pitch gable roof sitting low on the second story walls, as demonstrated in the Cross Section below.

Cross Section Elevation view showing Cape Cod style 2nd story

If you are unfamiliar with the tools to create this type of structure, please begin with Article Number 00358: Automatically Building a One and a Half Story Roof. Linked in the Related Articles section at the bottom of this page, before continuing with the steps outlined in this article to create your basic plan.

To create the dormer walls

  1. In floor plan, go up to Floor 2, then select Build> Wall> Straight Interior Wall , click and drag out an Interior Wall approximately 8' from the exterior wall.

  2. Use the Select Objects tool to select this Interior Wall, and click on the Open Object button to display the Wall Specification dialog.

  3. On the Roof panel, select Knee Wall in the Roof Options section and click OK.

  4. Next, select Build> Wall> Straight Exterior Wall and use this tool to create a room that will become the dormer.

    Floor plan view of house showing roof planes, ceiling lines, interior wall and exterior walls of dormer

  5. Go to Build> Wall> Break Wall to select this tool and place breaks on either side of the knee wall inside of the dormer.

  6. Now, use the Select Objects tool to select the center wall segment created by the breaks, and click on the Delete edit tool, or the Delete key on your keyboard, to remove it.

    Floor plan view showing middle section of Knee Wall deleted between dormer walls

Now that the dormer walls are in place, a hole in the roof plane will be needed to allow the walls to come through in order to create the dormer.

To create a hole in the roof

  1. From the menu, select Build> Roof> Skylight and either click to place a skylight polyline in the dormer area, or click and drag a skylight polyline around the dormer.

  2. Click to select the skylight polyline and use the square edit handles on each edge of the polyline to ensure that the front and sides of the polyline snap flush to the exterior of your dormer walls.

    Floor plan view showing Skylight placed over dormer walls

  3. With the Skylight still selected click Open Object to open the Roof Hole/Skylight Specification dialog.

  4. On the General panel, uncheck Skylight, and under Angle for Inside Hole Rim, select the radio button next to Plumb Sides.

  5. Click OK to apply these changes.

To draw the dormer roof planes

  1. Select Build> Roof> Roof Plane and draw two roof planes over the side dormer walls to form a gable condition.

    If prompted to with a Set Baseline Height dialog box, asking "Where would you like the new roof plane baseline to be located?", select "Over wall top".

  2. To ensure a proper ridge, use the Select Objects tool to select the ridge line edge of one of the newly drawn roof planes, click on the Join Roof Planes edit button, then click on the ridge edge of the second roof plane to join the two roof planes together.

  3. Selecting each roof plane, be sure to grab the front, gable eave edge line and pull it out, creating the eave overhang.

    Floor plan view showing roof planes over dormer walls connected after using Join Roof Planes

Note: If you are unfamiliar with either drawing, or manually editing roof planes in Home Designer Pro, please review the Roofs chapter of your Reference Manual from within the software by selecting Help> Launch help. Select the Contents tab, scroll down to the Roofs chapter, and click on the arrow next to it to expand out the chapter.

To adjust the shape of the roof hole

  1. Using the Select Objects tool, click to select the Roof Hole polyline, then click the Break Line tool in the edit toolbar and click to place a line break in the center of the top edge of the polyline, breaking this edge into two line segments that can be joined with the roof planes on either side.

    Floor plan view with Skylight selected and Break Line Edit Tool used to split back line segment

  2. Using the Select Objects tool again, select the top edge of the left dormer roof plane, click the Join Roof Planes edit button, then click on the left line segment of the Roof Hole polyline.

    Floor plan view showing one dormer roof plane joined to left line segment of Skylight

    The roof plane will angle its top edge in order to meet with the hole, which will cut and angle one side to join flush with the roof plane.

  3. Repeat this process for the right dormer roof plane.

    Floorplan view showing completed dormer with gable roof

    The remaining top edge of the roof hole will move and angle in order to meet flush with the reshaped roof plane, finalizing the dormer.

    If you receive a Warning dialog stating "Hole in roof, slab, countertop, or terrain object is not completely contained.", this occurs when the roof planes are too high, this means that the joined ridgeline is generating above the main roof ridge, which can be caused by a wide dormer. Either decrease the width of the dormer being created, manually lower the roof plane baselines or lower the dormer roof pitch.

Camera view showing completed dormer