Modifying Garage Floor and Stem Wall Heights

Reference Number: KB-01845
Last Modified: July 16, 2015

The information in this article applies to:

Home Designer Professional or Home Designer Architectural or Home Designer Suite or Home Designer Interiors


After changing the room type to Garage, my floor and ceiling heights changed. Why does this happen?


When Auto Rebuild Foundation is turned on, naming a room as "Garage" will cause changes to the way the foundation is built under that room.

First, let's begin with creating a basic example plan, where you will be using all of the default settings for Floor 1 floor and ceiling heights and for building your foundation.

To create the basic plan

  1. First, launch Home Designer and select New Plan to create a new plan, using the Default Style template.

  2. In the new plan file in floor plan view, select Build> Wall> Straight Exterior Wall , then click and drag out the walls to create a basic structure with attached garage, as shown in the image below.

    Once the main building and garage room have been created, the foundation is automatically created with the default stem wall and footing heights.

    The floor and ceiling heights in the room that you want to designate as the Garage are still at the default for floor 1. The Floor Height is 0" and in your case, the Finished Ceiling Height is 107 5/8".

  3. To verify this information, use the Select Objects tool to click on the smaller room, which will become your Garage, then click on the Open Object edit button.

  4. In the Room Specification dialog, notice the values set on the Structure panel.

  5. Next, select the General panel, and use the Room Type drop down menu to select Garage.

    When you changed the Room type on the General panel of the Room specification to Garage, the foundation was rebuilt to reflect these changes.

  6. Return to the Structure panel after specifying the room as a Garage and notice the changes

    • The Stem Wall Top (C) value is added to the Absolute Elevations and is set to the height of the underside of the floor joists on floor 1. The floor is changed to a slab and the slab is lowered 12" below the top of the stem wall.

    • The Stem Wall (I) is set to 22 1/2".

  7. Click OK to close the dialog for now.

    Note: You may want to change the Stem Wall (I) height to meet your frost depth needs, however, before making any changes to the Structure settings in the Room Specification, you must first turn off Auto Rebuild Foundation.

To visually see the changes that making the smaller room set to Garage, you can create a Full Overview .

To turn off Auto Rebuild Foundation

  1. Select Build> Floor> Build Foundation .

  2. In the Build Foundation dialog, remove the check mark next to Automatically Rebuild Foundation, and set the Minimum Garage Height to 37 1/2" to match the main house, and click OK.

  3. In the New Floor dialog, choose Derive new Foundation from the 1st Floor plan and click OK again.

  4. Use the Select Objects tool to click on the Garage room, then click on the Open Object edit button to again display the Room Specification dialog.

  5. On the Structure panel, observe that the Stem Wall height is 36" just under the garage so that the bottom of the footing matches the footing of the main house.

    The slab remains in its original position, 12" below the top of the stem wall, but the footing is moved down to accommodate the increased stem wall height.

  6. You can raise or lower the slab by modifying the Floor To SWT (H) value from Floor 1.

    In this example, a 6" curb is generated inside the garage by changing the Floor To SWT (H) value.

    Click OK to apply this change and close the dialog.

  7. Finally, create a Full Overview to see the change.

Now that you understand this procedure, you can take the knowledge you have gained and apply it to your own designs.