AECbytes Tips and Tricks Issue #68 (July 31, 2013)

Using Building Materials and Priorities in ArchiCAD 17

Thomas M. Simmons
President, ARCHVISTA Building Technologies

With the release of ArchiCAD 17, Graphisoft introduces a new method for managing Building Materials through automated building element connections called “Priority Based Connections.” This new feature provides intelligence in ArchiCAD so it understands the order in which elements are built and generates cleaned-up junctions automatically, based on rules. As you can see in the image below, through priority based connections, ArchiCAD will automatically connect structural elements such as a concrete floor and brick wall assembly while segmenting finishes such as wood flooring, interior partitions, and gypsum board.

So how does ArchiCAD understand how to manipulate these materials and manage their connections within your project? This is accomplished by assigning a “priority” to each building material so it can interact with other building materials based on the level of the priority assigned. In the Building Materials dialog, you can now assign an Intersection Priority to each skin of an assembly. A skin with a stronger intersection priority cuts the skins of the other structures with weaker intersection priority, as shown in the following example.

Priority Based Connections work with all construction elements in ArchiCAD which would include Walls, Columns, Beams, Slabs, Roofs, Shells, and Morphs. To understand how this concept works within a project, let’s review an example of a typical building assembly.

Before we start, let’s change the 3D Window so it shows cut elements with Building Materials rather than the default color of “09 Paint-08 Black”. To do this, go to the View menu and select Filter and Cut Elements in 3D... from the Elements in 3D View... sub-menu.

In the dialog box select Use Element Attributes in the Cut Surface Display panel.

Next, let’s create a typical intersecting building assembly between a wall and a slab. Open the Wall Tool, change the Wall Top to Not Linked and enter 20’. Next, select the “Brick Vr. 2x6 Wd Stud” option from the Composite Wall pop-up menu.

Click OK and draw a wall on the floor plan.

Next, open the Slab Tool settings, enter 10’ for the top of slab height and select the “Flr Cpt + Ply + 2x12 + GypBd” option from the Composite Slab pop-up menu.

Click OK and draw a slab to the outside of the Wall on the floor plan.

Select your Marquee Tool and draw a Marquee boundary intersecting the wall and slab. Right click and select Show Selection/Marquee in 3D. Now look in the 3D Window and you can see how ArchiCAD is prioritizing the material connections, allowing the sub-floor and wood joists to cut through the gypsum board finish and the wood framing within the wall.

To review and adjust the materials as well as the connections, select the slab in either the Floor Plan or 3D Window. Go to the Options menu and select Building Materials.

When an element is selected, the dialog can sort materials to show the building materials of the selected element at the top of the list. To do this, click the button in the upper left of the materials list. To adjust how a Building Material looks in Section, Floor Plan or the 3D Window, you can select different Fill patterns, Pen Settings and Material Color/Texture from the Structure and Appearance panel. In this panel, you can also set the Intersection Priority from weak to strong, which will then define how the skin of one element cuts the skin of an intersecting element. You can also change the names of Building Materials. For example if the name “Underlayment” is not correct in describing the material, then you can type in a new name called “Sub-Floor.”

To see how priorities work and can be adjusted, select the “Sub-Floor” and “Wood I-Joists” materials and set it to a weaker priority. You will see that it no longer cuts through the gypsum board finish or the wood framing in the wall.

To learn more about modeling through priority based connections as well as how to use ArchiCAD more efficiently in your practice, visit


About the Author

Thomas M. Simmons, the founder of ARCHVISTA, Inc. and LearnVirtual, has spoken at major industry events including AEC Systems, Ecobuild, AIACC Desert Practice Conference, and the AIACC Monterey Design Conference. He has authored several books on Building Information Modeling, ArchiCAD and architectural technology. He was formerly the Director of Technology with the award winning firm of EHDD Architects, San Francisco, and has earned a Masters of Architecture from UC Berkeley. He can be reached at


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