Fibre Reinforced Facade Encyclopedia: Design and detailing
Building information modelling applied to a facade is the practice of holding the cladding as a data-carrying three-dimensional model rather than as a set of drawings, so that geometry, panel identity, material, mass, fixing type, finish and test evidence all travel together in one place. On a panelised facade the model is the panel schedule, the setting out, the clash check, the sequencing tool and, at the end of the job, the asset record.
A facade drawing tells you a panel is 2,400 by 1,200. A facade model tells you it is panel EA-04-17, 2,412 by 1,198 on the as-built survey, 41 kilograms, mould family F12, satin finish, four bonded inserts, lifted in sequence 63, with the test report reference attached to it.
At a glance
| Property | Typical value | Note |
|---|---|---|
| Level of development | LOD 200 concept, 300 design, 350 coordination, 400 fabrication | BIMForum LOD Specification definitions |
| Exchange format | IFC 4, to ISO 16739-1 | Open format for cross-platform handover |
| Asset data schema | COBie | Structured handover of maintainable asset data |
| Information management standard | ISO 19650 parts 1 and 2 | Superseded PAS 1192 in the United Kingdom |
| Australian guidance | NATSPEC National BIM Guide | With the NATSPEC BIM Reference Schedule |
| Hard clash threshold | typically 10 to 25 mm | Set in the BIM execution plan, not assumed |
| Core panel data fields | Panel ID, mass, area, finish, fixing type, lift sequence | The fields the site actually uses |
| Fabrication geometry export | NURBS surfaces as IGES or STEP | Revit family geometry is often not sufficient for curved panels |
What the model is for on a facade
A facade model earns its cost in five ways: coordinating the cladding against the structure and the services at the slab edge, generating quantities and panel schedules that are consistent with the drawings because they come from the same source, producing setting out data for the installer, planning the installation sequence and the crane lifts, and handing over an asset record that tells a facility manager which panel is which in fifteen years.
None of those requires the model to be beautiful. They require it to be correct at the interfaces and consistent in its data. The most valuable part of a facade model is usually not the visible panel but the bracket, the cast-in, the rail, the cavity barrier and the slab edge condition, because those are where the coordination failures live.
Level of development, and why LOD 400 is a different model
Level of development describes how much a model element can be relied on, not how detailed it looks. LOD 200 is a generic placeholder of approximate size and location. LOD 300 is a specific element at a specific location, suitable for design coordination. LOD 350 adds the interfaces to adjacent elements, which is the level at which bracket to structure coordination becomes meaningful. LOD 400 is fabrication level: the element as it will actually be made, with real fixings and real tolerances.
The step from LOD 350 to LOD 400 is not an increment, it is a rebuild, and usually by a different party. A design team models the facade to coordinate it; a fabricator models it to make it, working from a survey of the structure as built and from mould geometry. Expecting the design model to become the fabrication model without that step is the most common false economy in facade BIM.
IFC, COBie and what actually transfers
IFC 4 is the open exchange format and it is good at geometry and at classified properties. It is weaker at parametric behaviour: relationships, constraints and rules generally do not survive a round trip, so treat an IFC export as a snapshot rather than as a live model. Put the information that matters into property sets attached to the elements, with agreed property names, so that it can be read by any tool rather than only by the authoring application.
COBie is the schema for handing over maintainable asset information: what the components are, where they are, who made them, and what maintenance they need. A facade contributes panels, sealants, fixings, cavity barriers and access equipment to a COBie deliverable. Decide early what level of the facade is a maintainable asset, because a COBie file that lists five thousand individual panels is as useless as one that lists the facade as a single line.
Clash detection worth running
Hard clash checking between the facade and the structure catches the obvious cases: brackets landing on reinforcement, cast-ins in the wrong position, rails passing through columns, and services penetrating the cavity. Run it with the threshold stated in the execution plan rather than at zero, or the report will be thousands of items long and will be ignored.
Two other checks matter more and are run less often. Soft clash, or clearance checking, tests whether there is room to install and later to maintain: whether a bracket can be reached with a spanner, whether a panel can be swung into place, whether a cavity barrier can be fitted after the rails are up. Tolerance clash tests whether the coordination survives the deviations that will actually occur, by rerunning the check with the structure offset by its permitted tolerance. A detail that clashes only when the slab is 20 mm out is a detail that will clash. See tolerances.
Handover to fabrication
The handover from model to factory needs four things agreed before modelling starts, and agreeing them afterwards costs a re-issue of everything. First, the geometry format and the software the fabricator will use, which for curved panels usually means a NURBS surface export rather than a native family. Second, a single project origin and orientation, stated in coordinates, used by every party. Third, units, stated explicitly. Fourth, the panel numbering convention, which has to be readable on a crate, sortable in a schedule and stable for the life of the project.
From there the fabricator derives mould geometry, cut files and shop drawings. The route is typically model to Rhino to CNC, with the panel schedule driving the production sequence. See shop drawings for the documentation that comes out of it, cnc formwork for what the geometry becomes, and parametric design for how the panel set was generated in the first place.
Standards and references
- ISO 19650-1 and ISO 19650-2 Organization and digitization of information about buildings and civil engineering works, including information management using BIM
- ISO 16739-1 Industry Foundation Classes (IFC4) for data sharing in the construction and facility management industries
- NATSPEC National BIM Guide and NATSPEC BIM Reference Schedule
- BIMForum Level of Development Specification
- COBie, as published within the United States National BIM Standard and ISO 19650-4 information exchange
- AS/NZS ISO 12006-2 Building construction: organization of information about construction works
- ISO 10303 (STEP) and IGES for exchange of surface geometry to fabrication
Related terms
Questions specifiers ask
What level of development does a facade model need?
LOD 300 for design coordination, LOD 350 to coordinate the interfaces where brackets meet the structure, and LOD 400 for fabrication. The step to LOD 400 is normally a rebuild by the fabricator against a survey of the structure as built, not an increment on the design model.
Does IFC carry everything in the model?
It carries geometry and classified properties well, but parametric relationships and constraints generally do not survive a round trip. Treat an IFC export as a snapshot, and put the information that matters into agreed property sets so any tool can read it.
What is COBie used for on a facade?
Structured handover of maintainable asset data: panels, sealants, fixings, cavity barriers and access equipment, with manufacturer and maintenance information. Decide early what counts as a maintainable asset so the file is neither one line nor five thousand.
Which clash checks actually matter?
Hard clashes between brackets, cast-ins and structure, plus two that are often skipped: clearance checks for installation and maintenance access, and a rerun of the check with the structure offset by its permitted tolerance.
Can a fabricator work directly from a Revit model?
For flat panels sometimes; for curved panels rarely. Curved geometry is usually exported as NURBS surfaces in IGES or STEP. Agree the format, the project origin, the units and the panel numbering before modelling starts.
Handing a facade model to fabrication? We can agree geometry format, origin, units and panel numbering with your design team before the model is built. Talk to our engineering team
Reviewed by Richard Halvorsen, General Manager, ShapeShift Technologies. Last updated September 2026.