Modifying Garage Floor and Stem Wall Heights

The information in this article applies to:


After naming my Garage room, the floor and ceiling height information changed. Why does this happen?

Adjust foundation heights for stem walls and garage areas


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

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

To create the basic plan

  1. In a 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.

    Floor plan showing two areas - main house and attached garage

    Once the main building and garage room have been created, the foundation is automatically created with the default stem wall and footing heights.
    If your foundation does not automatically generate, click Build> Floor> Build Foundation  , put a check in the Automatically Rebuild Foundation box and click OK.

    The floor and ceiling heights in the room that will be designated as the Garage are still at the default for Floor 1. The Floor height is 0″ and in our case, the Finished Ceiling height is 107 5/8″.

  2. To verify this information, use the Select Objects tool to click on the smaller room on Floor 1, which will become the Garage, then click on the Open Object edit button.
  3. In the Room Specification dialog, notice the values set on the Structure panel.

    Room Specification dialog on Structure panle with Floor height of zero and Finished Ceiling height set to 107 5/8

  4. Next, select the General panel, and use the Room Type drop-down menu to select Garage, then hit OK.

    Room Specification dialog on General panel with Garage selected as the Room Type

    When the Room type is changed, the foundation is rebuilt to reflect these changes.

  5. Open  the garage room to specification and return to the Structure panel to see the changes.

    Room Specification dialog with Structure panel selected showing -14 1/8 Stem Wall Top and Finished Ceiling of 134 5/8

    • The Stem Wall Top height 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 height is set to 22 1/2″.
    • The Floor Finish is set to 0″ and the Floor Structure becomes a 4″ concrete slab.
  6. Click OK to close the dialog and take a Perspective Full Overview to see the results so far.

    Perspective Full Overview showing foundation under house and garage

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 dialog, you must first turn off Auto Rebuild Foundation.

To turn off Auto Rebuild Foundation

  1. Select Build> Floor> Build Foundation .
  2. In the Build Foundation dialog, remove the check next to Automatically Rebuild Foundation, then click OK.

    Build Foundation dialog with the box for Automatically Rebuild Foundation option cleared

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

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

  4. Use the Select Objects tool to click within the Garage room on the Foundation level, and click on the Open Object edit button to display the Room Specification dialog.
  5. On the Structure panel, select the Default option next to Stem Wall to set the Stem Wall height to 37 1/2″ to match the stem wall created for the main house.

    Room Specification dialog with Stem Wall set to Use Default

    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 value.

     Room Specification dialog with 6 inches entered for Floor to SWT

    • To create a 6″ curb, or stem wall above the slab, set this value to 6″.
    • Click OK to apply this change and close the dialog.
  7. Finally, select 3D> Create Perspective View> Perspective Full Overview  to  see the change.

    Perspective Full Overview showing new matching foundation under garage and house

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