Family Matters: Essential Clearances and Boundaries
If you’ve ever played the “I’m not touching you” game as a child, you know the importance of boundaries and our need for space. Autodesk® 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
ADA Access
Installation Space
Code Clearance
Access & Maintenance
Air Movement
Aesthetics
Safety
A book could be written about Revit families; this article will 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.
To demonstrate adding a clearance to an existing family, we will be using the “Condenser – Air Cooled – Horizontal – 301-455 MBH.rfa” file.
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.
Figure 1
In the Object Styles box, change your Clearance Zone Line Color to “Red” and Line Pattern to “Hidden.”
Figure 2
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” (Figure 3).
Figure 3
Rename the duplicate to “Clearance Zone,” change the color to Red and choose your transparency setting.
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 needs the clearance—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.”
Figure 4
Name it clearance depth or something to that effect. This is how you name all your reference planes.
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 Create Tab, 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.
Figure 5
Figure 6
Figure 7
Tip: Make the rectangle larger than the reference planes. Hit ESC twice. Now you can align the extrusion model lines to your reference planes. After each alignment, lock it so it cannot be moved (Figure 9).
Hit the green checkmark when finished. Go to an elevation view so we can correct the depth. Repeat process of Align and Lock. Open up your 3D View and admire your work! Select the clearance and change the Material and Subcategory settings.
Figure 8
Figure 9
Tip: You create a subcategory 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.
Figure 10
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.
Figure 11
Voilà! We have an excellent clearance that is part of this family, but easily manipulated for your needs.
Jennifer Lanzetti is a principal of Cn3D Construction; assisting the AECO industry to fill the gap between great building technologies and the implementation of these tools. Her career in construction began as a laborer in high school and has progressed to overseeing all phases of commercial construction. With a passion for Building Information Modeling, lean construction, the integrity of information she understands the need for a different approach to construction. She is a prominent voice supporting the industry shift away from the design-bid-build delivery method to an Integrated Project Delivery process. Her energy is dedicated to the evolution of building, and living, in a collaborative world; given the immense and noble responsibility we have of providing people shelter and public resources.
Travis Beecher is no stranger to the BIM world and Revit modeling. Travis graduated from ITT Technical Institute in 2001. He started his career in engineering with lighting design. From there he jumped into the mechanical side of the engineering field and has helped create and run mechanical drafting departments. He is consistently asked Autodesk to join the Gunslinger program to help develop and Beta test future releases of Revit. Travis currently works as a Senior BIM Engineer bringing strong Revit skills along with intimate knowledge of MEPF systems to the Cn3D team. In his spare time Travis enjoys spending time with his three children, playing music, going to the races and spending time outdoors.
