Modifying Garage Floor and Stem Wall Heights

Reference Number: KB-01845
Last Modified: July 21, 2021

The information in this article applies to:

Home Designer Professional or Home Designer Architectural or Home Designer Suite


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

House structure with stem walls


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.

    36 x 36 main house with 24 x 24 attached room

    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.

    Room Specification showing defaults for floor and ceiling heights

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

    Selecting Garage for the Room Type

    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

    Room Specification dialog - Structure panel - new values for Stem Wall Top, Floor, Stem Wall and Floor to SWT

    • The Stem Wall Top 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 is set to 22 1/2".

  7. Click OK to close the dialog for now.

    Note: You may want to change the Stem Wall 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 Automatically Rebuild Foundation.

To visually see the changes created by making the smaller room a Garage type room, you can create a Perspective Full Overview camera view.

Perspective Full Overview showing a different foundation under the garage

To turn off Automatically Rebuild Foundation

  1. Select Build> Floor> Build Foundation .

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

    Build Foundation dialog with Automatically Rebuild Foundation option deselected

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

    Derive new foundation plan from the 1st floor plan option selected in the New Floor dialog

  4. Select Tools> Floor/Reference Display> Up One Floor to return to Floor 1.

  5. 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.

  6. On the Structure panel, change the Stem Wall value to 36". in Home Designer Pro, observe that the Stem Wall height is already 36". This stem wall height is 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.

  7. You can raise or lower the slab by modifying the Floor To SWT value from Floor 1.

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

    Room Specification dialog with -20 1/8" Floor value, 6" Floor to SWT value and 36" Stem Wall value

    Click OK to apply this change and close the dialog.

  8. Finally, create a Perspective Full Overview to see the change.

    Perspective Full Overview showing stem wall and footing the same for whole house and garage

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