Inspect IFC property sets: a guide to Pset_*

When you click an element in an IFC viewer, you usually see two kinds of data: the element's direct attributes (Name, GlobalId, Tag…) and a list of property sets, conventionally named Pset_*. This is a short guide to what property sets are, why they matter, and how to read them.

What is a property set?

A property set is a named bag of key-value pairs attached to one or more IFC elements via an IfcRelDefinesByProperties relationship. Each value is typed (string, real, integer, boolean, enumeration, etc.) so downstream tools can validate and use them.

buildingSMART maintains a registry of standardised property sets named Pset_* (with the prefix). Authoring tools can also attach custom property sets — typically named after the company or domain (MyCompany_FireRating, RebarSpec, etc.). Both kinds appear the same way in a viewer.

Common standardised psets

Pset_WallCommon

Attached to walls. Typical fields: Reference (designation), IsExternal (boolean — interior vs façade), LoadBearing, FireRating, AcousticRating, ThermalTransmittance (U-value).

Pset_SlabCommon

Attached to slabs. Includes IsExternal, LoadBearing, FireRating, SurfaceSpreadOfFlame, Combustible.

Pset_DoorCommon

Attached to doors. Includes FireRating, AcousticRating, IsExternal, SecurityRating, Reference.

Pset_QuantityTakeOff

Attached to anything quantity-relevant. Holds takeoff quantities authored by the BIM tool — useful for rough cost or material estimates.

BaseQuantities (technically a quantity set, not pset)

Attached to physical elements with measurable extents. Contains Length, Width, Height, NetArea, GrossVolume, etc. — the values your QS team actually wants.

Custom property sets

Anything not prefixed Pset_ is custom. These are normal — every authoring tool exports its own, and large practices add company-wide ones for classification (UniClass, OmniClass), specifications, or asset IDs.

If you see a property called something like MyOffice_RoomFinish.FloorMaterial, it was added by the author and is meaningful only within their workflow. Treat custom psets as informational unless you have documentation from the author.

How to read property sets in IFC Navigator

1. Open your IFC file in IFC Navigator.
2. Click any element in the 3D view.
3. The right-side panel opens. The first group is the element's IFC type and direct attributes (Name, GlobalId, Tag, etc.).
4. Each subsequent group is a property set, with its name as the heading and a two-column key/value list below.

Common gotchas

• Empty pset. The author defined the pset but did not fill in values. IFC Navigator hides empty rows so you only see populated properties.
• Different units. Always check the project units (often metres or millimetres) — IFC viewers do not always normalise.
• Element type vs occurrence. Some properties live on the type (e.g. IfcWallType) rather than the occurrence (the placed wall instance). A good viewer follows the relationship and shows both.