Family Matters: The Importance of Clearance and Boundaries

This blog post was originally written for the Cn3D Construction blog. Cn3D Construction is now a U.S. CAD company, so please check back here at for more written articles from Jennifer Lanzetti and our new U.S. CAD Utah team.

If you’ve ever played the “I’m not touching you game” as a child, you know how important boundaries are and our need for space. Revit families are no different. A 3D element provides a great parametric visual of what we can expect outside of the virtual world, but without the proper clearances the equipment may not be given the space it truly needs to function.

Clearances Reasons: 1) ADA Access, 2) Installation Space, 3) Code Clearance, 4) Access & Maintenance, 5) Air Movement, 6) Aesthetics, 7) Safety

To demonstrate adding a clearance to an existing family, we will be using the ‘Condenser – Air Cooled – Horizontal – 301-455 MBH.rfa’ file. A book could be written about Revit Families; this article is going to focus on adding a correct clearance zone to your family while keeping it separate from the model element. During design review and clash detection, we want to be sure the clearance zone is easily identifiable versus the actual Family.

With this family open, navigate to your Visibility Graphics (VG), select ‘Object Styles’, click ‘New’ under the Modify Subcategories and call your New Subcategory ‘Clearance Zone’. Making sure that the correct ‘Subcategory of’ is selected.

visibility graphics blog
clearance zone line pattern blog

Next we need to create a Clearance Zone material. A semi-transparent material is ideal. I prefer to duplicate the glass material and change the color. In the Manage tab, select Materials. Select ‘Glass’, then ‘Duplicate Selected Material’.

clearance zone graphics blog

Rename the duplicate to ‘Clearance Zone’, change the color to Red and choose your transparency setting.

clearance zone red blog

Now the best part, adding our clearance to the family. If only it was this easy in our real lives. Revit provides you with two Reference Planes [Center (Front/Back) and Center (Left/Right)] and one for the elevation. (Note: If you are customizing a current Revit family, you will notice many reference planes are already created.) In order to create a 3D boundary, you will need a reference plane on each side of the equipment that the clearance is needed; Front, Side, Back Bottom and/or Top.

The condensing unit needs access on the connections side only. Although it is important to always check the submittals! When creating your reference planes, make sure to name them and apply a reference line priority (high, weak or none). Open up your plan view, front and right elevation view. Navigate to the Create Tab and select Reference Plane. Add the needed reference planes and dimension. In the Options Bar, Select Label and ‘Add Parameter’.

add parameter blog
name reference plane blog

Tip: ‘Type’ is a parameter that is consistent throughout a project, whereas ‘Instance’ is for one-of-a-kind families. If you change a Type parameter, it adjusts all of those families simultaneously.

Next we will create the extrusion for the clearance. Open the floor plan, navigate to the CreateTab and select Extrusion. This will activate the Modify/Create Extrusion Tab. You can select whichever Draw function is easiest. For this example we will use the ‘Rectangle’ option.

3D view blog
change clearance zone blog

Tip: The reason why you create a subcategory, is so you can manipulate it in your Revit project, without having to open up the family (change color, change visibility, etc.).

A final adjustment option is in Family Visibility Settings. If you have 57 VAV boxes with clearances in a project, having to generate the clearances with each view change could slow your model down. You can adjust how and when your clearances are shown here.

If you choose this option please notify the design and construction team so they select the correct Detail Level when exporting out the model.

visibility settings detail levels blog

Tip: One final word on families. Adjust the Revit Family Template to match your company standards. That way you can create your material and subcategory once versus individually with each family.

Voilà, we have an excellent clearance that is part of this family, but easily manipulated for your needs.

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