FreeCAD Arch Site: Structural Site Object Explained

In FreeCAD's Arch and BIM workbenches, the Site object serves as the spatial foundation of an architectural project, representing the physical terrain, geographical coordinates, and boundaries of a plot of land. This article explains what the Arch Site object is, its key functions, essential properties, and its role in organizing building elements and exporting standard Industry Foundation Classes (IFC) data.

Definition of the Arch Site Object

The Arch Site is a specialized grouping object used to define a real-world construction site. It acts as the top-level spatial container in an architectural project hierarchy. In standard Building Information Modeling (BIM) workflows, a Site typically encompasses one or more Building objects, exterior landscaping elements, roads, and native terrain geometry.

When exporting a project to IFC format, the Arch Site translates directly into an IfcSite entity, ensuring proper spatial referencing in collaborative BIM environments.

Primary Functions of the Site Object

1. Spatial Organization

The Site object organizes complex project hierarchies. While child objects such as walls, slabs, and structural columns typically reside inside Storeys (Levels) and Buildings, the Site acts as the master parent container. Moving the Site automatically shifts all nested elements, maintaining spatial consistency.

2. Terrain and Topography Modeling

An Arch Site can incorporate topographical geometry. You can generate a 3D terrain surface directly from:

  • 2D contour lines (imported from DXF, DWG, or sketch lines)
  • Point clouds or coordinate sets representing ground elevations
  • Standard 3D meshes and solids

Once added to a Site, FreeCAD can compute cut-and-fill operations to calculate earthwork volumes required for excavations and foundations.

3. Geographic and Solar Positioning

The Site object anchors your project to real-world coordinates. This data is critical for accurate shadow studies, solar analysis, and daylight modeling using FreeCAD's integrated tools or external renderers like Ladybug.

Key Properties of the Site Object

When you select a Site object in the FreeCAD tree view, the Property panel provides several critical parameters:

  • Latitude and Longitude: Decimal or degree-based geographic coordinates used to pinpoint the exact location on Earth.
  • Elevation: The reference height of the site above sea level.
  • North Deviation (Declination): The angle difference between the project's drawing orientation (true horizontal/vertical grid) and true geographic north.
  • Terrain: Specifies the linked base shape or mesh that defines the ground surface.
  • Postal Address: Metadata fields for street, city, country, and postal code to enrich the IFC dataset.
  • EPW File: The path to an EnergyPlus Weather file used for localized climate and solar simulations.

How to Create and Use a Site in FreeCAD

  1. Switch to the BIM or Arch workbench.
  2. Ensure you have your project elements or terrain shape selected (optional).
  3. Click the Site tool icon from the toolbar or choose it from the menu.
  4. Drag and drop existing Building objects or structural elements into the newly created Site folder in the tree view.
  5. Set the latitude, longitude, and elevation in the Data tab of the Property view.

Using the Arch Site object guarantees that your FreeCAD model adheres to international BIM standards, provides accurate environmental data, and maintains a clean structural hierarchy.