Element Intersections and Junctions in Archicad

Every construction is built using multiple materials, so is the (BIM) model inside Archicad.

When different parts of a model with different Building Materials intersect, the junction between these elements will be made according to some rules.

In this article, you will read about:

• Intersection basic principles.
• Different intersection and junction cases.
• Tips to have clean intersections.

Intersection basic principles

Core principles

There’s three major points that determine how elements intersect in Archicad:

1. All construction element junctions will clean up in the condition that they collide.
2. The junction depends on Building Materials priorities, the skin (material) with the higher priority will cut through the one with lower priority. The Building Materials dialog box can be accessed through: Options > Element Attributes > Building Materials.

3. In order for roofs, shells and morphs to intersect properly, they must collide and be merged or trimmed by using the Connect menu.

Automatic intersections

Automatic intersections will modify the geometry of the elements involved. This modification is made at the skin level (building material).

These intersections are made on the base of one of the following methods, depending on?the elements involved:

1. Collision:

This means that the elements have to collide in the model.

This method is used for when these elements are involved: wall, beam, column and slab.

For the Wall-Wall junction, reference line intersection is required.

There are two exceptions where Solid Elements Operations is required: Column-Column and Slab-Slab intersections.

2. Reference Line Intersection

This means the reference lines must intersect.

This method is used for Wall-Wall and Beam-Beam junctions.

To show the Reference Line, activate this option from: View > On-Screen View Options > Wall & Beam Reference Lines.

There is the Auto Intersection option (from the Options menu). When this option is enabled, walls and beams with the reference lines close to each other will automatically extend to intersect. This option is enabled by default.

3. Wrapping

This method is available only for column-wall intersection (not available for complex profile columns).

When you place a column that intersects with a composite wall, you have the choice to either wrap the column so it will break the core skins, or not.?

These two are Wrapping Methods?that you can access from default or selected column settings.

Junction Order

For walls and beams with equal priority, use the Junction Order from the Wall or Beam Selection or Default Settings?to specify which walls meet first, and which will join the intersection last.

You can set a value from 0 to 16, so you can set exactly in what order each wall or beam will join the intersection.

In this example, there are two walls with the same Building Material Priority intersecting (with override cut fill pens) that normally will intersect as they do on the left in the image below because the default value of Junction Order. But if you want the orange wall to pass through the blue one, you change the value to 8 and you will have the result as the right in the image below.

Intersections based on Layers and Layers Combinations

Archicad offers another way to control how elements intersect regardless Building Materials Priorities.

In the Layers Settings dialog box, there's a column where you set the Layer Intersection Group for each layer.

Intersecting elements that belong to the same?Layer Intersection Group will be joined to each other. Elements on different?Layer Intersection Groups will not be joined.

If two or more elements are set to the Layer Intersection Group 0, they won't intersect.

By default, every layer is set to Group 1, so all intersecting elements will be joined.

Elements with the same intersection groups will intersect even if one of the layers is hidden. Some missing line can result?due to this intersection with an element on a hidden layer. To avoid this, select one of the layers, and assign it any different intersection group.

If you have many layers that you need to change the Intersection Group automatically you can use the Intersections in Layer Combinations Add-On from the Options menu.

The Intersections in Layer Combinations Add-On will set, for each Layer Combination, a Layer Intersection Group value 1 to all visible layers, and a value 2 to all invisible layers.

Different intersection and junction cases?

Slab Finishes and Opening Thresholds

When the top of a Slab is flush with the top of a Wall Opening, the Slab's finish skins will continue through the Wall regardless of building materials intersection priorities.

In the other case (slab is not flush with the top of a wall opening), the standard priority-based connections will be made.

Intersections involving Shell, Roof, or Morph

If a Shell, Roof or Morph is included in the intersection, use Design > Connect > Merge Elements to ensure accurate intersections.

If a Shell or Roof is used as a trimming element, use Design > Connect > Trim Elements to Roof/Shell, it will be merged automatically with the trimmed element.

Once merged, the element with the higher-priority Building Material will cut the one of a lower priority.

Element intersection order

When various, colliding construction elements have the same intersection priority, the following intersection order will prevail:

Morph > Column > Beam > Slab > Wall > Shell > Roof > Mesh

Tips to make elements collide

• Define the Core as Reference Line / Plane. By doing this, the Wall/Slab core connections remain the same when you edit the wall or slab.

• Link walls and columns Top to the story above so these elements remain connected properly if you edit story height.

• Adjust Elements to Slabs, adjust walls, columns and horizontal beams to specific levels of one or two slabs, from the Edit menu: Edit > Reshape > Adjust Elements to Slabs.

Note that the walls here are adjusted to Core Bottom and Core Top for better and clean junctions.

Here I shared with you how I manage element intersections and junctions in Archicad.

Hope this helps.

If you like this kind of article / tutorials, please subscribe to the AIM DESIGN Tutorials newsletter.