Sub-grade Work

This page covers the construction that occurs below grade. This includes building pads, foundation walls, and footings. 

Insert exterior slabs, foundation walls and footings throughout your project.

SG.1. Interior Concrete Slabs with Foundation Walls

Inserting a basic concrete slab floor in an interior space is described in the Building Elements page. If you have an area that does not have a slab on grade, but instead has a basement level below it, refer to the instructions below. If you do not have a basement, go to SG.1.5.

SG.1.1. If you have a basement level, create a level for it. If Level 1 is at 0'-0", your set your Basement level to -9'-0". Rename the level to Basement by clicking on the text.

SG.1.2. Go to your new Basement level and change the Underlay so Level 1 is visible.

SG.1.3. Draw foundation walls for your basement. Typically, these walls are 10"-12". 

SG.1.4. Draw a 5" concrete slab inside those walls. 

SG.1.5. Draw shallower foundation walls below your exterior walls wherever you have slabs on grade. Foundation walls must be below the frost line. The frost line varies depending on local temperatures.

SG.2. Modifying the Building Pad

SG.2.1. The building pad is the area within the toposurface where your building is placed.  In the section image below the toposurface is within the basement space. To carve out the basement space we will need to generate a building pad below the slab. If you do not have a basement, you do not need to complete this series of steps.


SG.2.2. To generate a building pad go to the Site view. Click on the toposurface, go to the Massing and Site ribbon and select building pad.

SG.2.3. Change the building pad settings as shown below. The thickness shown in the image is 0'-1/4". Sometimes the building pad acts as a slab, but I find that this presents problems when you want to place components on the basement level. Inserting a slab on grade in addition to a building pad works better for this purpose.

SG.2.4. Draw the exterior profile of your foundation walls and lock the lines in place so the pad moves with your foundation walls.  

SG.2.5. The image below shows the section with the new building pad. 


SG.3. Adding Footings to your Foundation Walls

SG.3.1. Temporarily hide the toposurface. Go to a 3D view and look at the project from the bottom. The image below shows a slab at the bottom of a basement level. If you do not have a basement level you will just see the bottoms of the foundation walls.

SG.3.2. Go to the Structural ribbon and select Wall on the Foundation panel.

SG.3.3. Select the bottom of each of your foundation walls. In the image below 1 & 2 have been selected. In the image below the footing has been added to the foundation walls for a building with a basement.


In the image below the footings have been added to the foundation walls for a building with a basement.


In the image below a foundation has been added to the foundation walls for a building with no basement.

The footings at the basement are visible in the section image below.


The footing for a slab on grade with no basement is shown in the section image below.

SG.3.4. Add footings to all of your foundation walls. 

SG.4. Exterior Slabs

You may want to include concrete slabs in some of the exterior areas in your project. This could include the walkways that lead from the parking to the doors. It may also include the area around the pool. For these slabs there typically is no foundation wall, but the edges may have profiles.

Adding exterior slab is the same process as putting a  floor into the interior areas of your project. You simply draw the profile. Thicknesses will vary. You might construct this out of a 5" concrete slab. One recommendation is that the top of the slab be an inch below the interior level. 

SG.5. Creating a Slab Edge Profile

Note: This work is part of the next exercise. 

You can alter the edges of floors and slabs. For example, if you are working with a thickened slab instead of a foundation wall, you can generate a thickened edge profile for the slab. Check to see if there is a family that suits your needs. If not, you can generate your own profile. Another instance where you might alter the edge of a floor is in the transition between concrete sidewalks and asphalt pavement. In this case you would add a curb to the edge of the concrete slab.  

SG.5.1. Typically, cars park on the pavement which is a few inches below the sidewalks. A curb separates the concrete slabs and pavement. One way to do this is to make a custom profile for the edge of the slab. The steps described below are one way to do this. A profile is a type of family. To make a new profile, make a new Family by choosing the Profile-Hosted template. The profile will be hosted by the concrete slab.

SG.5.2. Once in the new profile family, create a new reference line that represents the bottom of the slab.

SG.5.3. Use line work to construct the edge of the slab.

SG.5.4. Use the Fillet tool to make a radiused corner.


SG.5.5. Save the profile family and load the profile into your Revit project.

SG.5.6. On the Architecture ribbon select Floor: Slab Edge under the Floor Pull down. The default slab edge will appear n the Properties window. You will need to create a new type by making a Duplicate of the one that is loaded.

SG.5.7. You will need to create a new type by making a Duplicate of the one that is loaded.

SG.5.8. Next, assign the profile you created to the slab edge.

SG.5.9. Choose your slab edge from the Floor Slab Edge types.

SG.5.10. Select the edges of the slab that will receive the slab edge.  Not all edges of your slabs will receive a curb. Just the ones that meet pavement.