Level of Development (LOD) is one of the most important yet frequently misunderstood concepts in Building Information Modeling. For precast concrete, where BIM models serve as the basis for everything from conceptual cost estimates to production shop drawings, getting the LOD right at each project phase is critical. Too little detail early on and you cannot make meaningful design decisions. Too much detail too early and you waste engineering hours on elements that will inevitably change. The BIMForum LOD Specification provides the industry framework for defining what each LOD level means, but its general guidance must be interpreted specifically for precast concrete applications. This article provides that interpretation, explaining exactly what LOD 100 through LOD 500 mean for precast elements, and how DesignLogic plugins support progressive LOD refinement from early design through fabrication.
What LOD Actually Means
Level of Development defines the degree to which the geometry and attached information of a model element have been thought through, the degree to which model element geometry and information can be relied upon by other stakeholders. It is not simply the visual resolution or graphical detail of the model. A highly detailed 3D rendering of a precast panel might look impressive but carry no reliable dimensional or structural information, making it essentially LOD 100 despite its visual sophistication. Conversely, a simple extruded box with accurate dimensions, material properties, weight, and connection data might constitute LOD 350 or even LOD 400.
The BIMForum LOD Specification, first published in 2013 and updated regularly since, defines five primary levels of development: LOD 100, LOD 200, LOD 300, LOD 350, LOD 400, and LOD 500. Each level represents a progressively more complete and reliable representation of the element. For precast concrete, the transitions between levels correspond closely to the project phases familiar to every precast producer: conceptual design, schematic design, design development, construction documentation, and fabrication.
Important Distinction: LOD vs. LOG vs. LOI
The industry sometimes separates Level of Development into Level of Geometry (LOG) and Level of Information (LOI). LOG refers to the graphical completeness of the 3D model, while LOI refers to the non-graphical data attached to the element (material properties, structural capacity, cost data, etc.). For precast, both dimensions matter. A wall panel at LOG 300 with LOI 400 has accurate geometry but also includes reinforcement data, finish specs, and weight calculations that go beyond what the geometry alone shows.
LOD 100: Conceptual Representation
At LOD 100, a precast element is represented as a conceptual placeholder. The element exists in the model to indicate that a precast component will occupy a particular volume of space, but its specific geometry, dimensions, and properties are not yet defined. A precast wall panel at LOD 100 might be a simple rectangular extrusion representing the approximate envelope of the building facade, with no information about individual panel sizes, joint locations, or panel thickness.
What LOD 100 Includes for Precast:
- Geometry: Approximate overall building envelope or zone allocation. May be a single mass representing "precast facade" or "precast structure" rather than individual elements.
- Reinforcement: None. No reinforcement is modeled at this stage.
- Connections: None. Connection locations and types are not defined.
- Embeds: None.
- Finishes: General finish intent may be noted in text (e.g., "architectural precast") but not modeled.
Appropriate Uses: Conceptual cost estimating based on square footage or cubic yards, massing studies, feasibility analysis, and early energy modeling for thermal mass evaluation. LOD 100 models should not be used for structural analysis, piece counting, or any purpose that requires accurate element dimensions.
LOD 200: Schematic Design
At LOD 200, precast elements are modeled as individual objects with approximate geometry. Each element is recognizable as its intended type: a wall panel looks like a wall panel, a double tee looks like a double tee, a column looks like a column. However, the dimensions are approximate and subject to significant change as the design develops. Panel joints are located at approximate positions, member depths are preliminary, and the overall structural layout is still being refined.
What LOD 200 Includes for Precast:
- Geometry: Individual precast elements with approximate dimensions. Panel widths and heights are close but not final. Member depths are based on preliminary sizing. Blockouts and openings are shown at approximate locations.
- Reinforcement: Not modeled. Reinforcement quantities may be estimated based on rules of thumb for cost estimating purposes.
- Connections: Connection zones identified (e.g., "connection here between beam and column") but specific connection types and hardware not defined.
- Embeds: Not modeled. Embed counts may be estimated for cost purposes.
- Finishes: Finish type assigned as a property (e.g., "acid etch," "sandblast," "form liner") but not geometrically modeled. No reveals, rustications, or return edges shown.
Appropriate Uses: Preliminary cost estimating with piece-count accuracy, coordination with the architect on panel layout and joint patterns, initial structural analysis for member sizing, and preliminary erection sequence planning. LOD 200 is typically the level at which precast producers first become involved in the project, providing budgetary pricing based on approximate quantities.
LOD 300: Design Development
LOD 300 is where precast BIM models become genuinely useful for engineering and production planning. At this level, every precast element has accurate dimensions that can be relied upon for structural design, coordination, and quantity takeoffs. The model is dimensionally correct: panel widths, heights, and thicknesses reflect the actual intended design, member depths and spans are finalized, and openings are located at their true positions and sizes.
What LOD 300 Includes for Precast:
- Geometry: Accurate element dimensions including panel widths, heights, thicknesses, and all reveals, chamfers, and blockouts at correct locations and sizes. Dapped ends, corbels, and ledges are modeled geometrically.
- Reinforcement: Preliminary reinforcement layout. Primary flexural and shear reinforcement is modeled or defined parametrically. Strand patterns for prestressed members are established. Exact bar sizes and spacing may still be subject to final design confirmation.
- Connections: Connection types are defined (welded plate, grouted dowel, bearing pad, etc.) and located at correct positions. Connection hardware is modeled schematically but may not include every individual bolt and weld.
- Embeds: Primary structural embeds are modeled at correct locations with approximate sizes. Miscellaneous embeds (MEP sleeves, conduit boxes) may not yet be included.
- Finishes: Finish types assigned to specific faces. Architectural reveals and rustications modeled geometrically. Form liner patterns identified but may not be modeled at full resolution.
Appropriate Uses: Accurate quantity takeoffs for competitive bidding, structural design and analysis, multi-trade coordination (clash detection with MEP, steel, and other systems), erection planning with accurate piece weights and dimensions, and initial production planning. This is typically the minimum LOD required for DesignLogic to perform a meaningful data extraction to CastLogic ERP.
LOD 350: Construction Documentation
LOD 350 was introduced by the BIMForum to address a gap between LOD 300 and LOD 400 that is particularly relevant for precast concrete. At this level, elements are modeled with sufficient detail and accuracy for construction coordination, including interfaces with adjacent building systems. The model includes not just the precast elements themselves but also their relationships to the surrounding structure: how they bear on structural steel, how they interface with curtain wall framing, where they conflict with MEP runs, and how they connect to the cast-in-place foundation.
What LOD 350 Includes for Precast:
- Geometry: All LOD 300 geometry plus accurate support conditions, bearing surfaces, and interface details with adjacent systems. Joints between panels are modeled at correct widths. Edge conditions (returns, miters, quirks) are defined.
- Reinforcement: Complete reinforcement layout with final bar sizes, spacing, and bend configurations. Bar positions verified against clearance requirements. Strand patterns finalized with depression points and debonding patterns.
- Connections: All connection hardware modeled with accurate geometry: embed plates with stud patterns, angles with bolt holes, weld plates with weld sizes indicated, bearing pads at correct sizes and locations.
- Embeds: All embeds modeled including structural connections, MEP penetrations, conduit boxes, sleeve locations, lifting hardware, and miscellaneous inserts. Embed locations are coordinated with reinforcement to avoid conflicts.
- Finishes: Complete finish specification on all faces. Form liner patterns modeled at sufficient resolution for coordination. Exposed aggregate depth, sandblast depth, and acid etch areas defined.
Appropriate Uses: Multi-discipline coordination and clash detection, construction document production, detailed cost confirmation, erection drawing development, and production scheduling. LOD 350 is the level at which most precast producers finalize their engineering and prepare for production.
LOD 400: Fabrication
LOD 400 is the fabrication-ready level. At this stage, the model contains sufficient detail and accuracy to fabricate the precast element directly from the model data. Every dimension, every reinforcing bar, every embed, and every surface treatment is defined to the precision required for production. This is the level at which DesignLogic's full BIM-to-production pipeline operates, extracting complete fabrication data from the model and transmitting it to CastLogic ERP for production scheduling, material procurement, and quality control.
What LOD 400 Includes for Precast:
- Geometry: Production-accurate geometry including all chamfers, drip edges, keyways, blockouts, haunch pockets, and form complexity. Dimensions are exact to the tolerances specified in PCI MNL-135 (Tolerance Manual for Precast and Prestressed Concrete Construction).
- Reinforcement: Every individual reinforcing bar modeled with exact cut length, bend dimensions, and placement location. Complete bar bend schedules can be extracted. Strand patterns with exact strand-by-strand positions, including any intentionally debonded strands with sheathing lengths.
- Connections: Every connection component modeled at fabrication detail: exact plate sizes and thicknesses, stud diameters and lengths, hole sizes and patterns, weld sizes and lengths, grout pocket dimensions, and bearing pad durometer and size specifications.
- Embeds: All embeds with exact part numbers, supplier specifications, and placement tolerances. Lifting hardware with capacity ratings and SWL (Safe Working Load) markings. Threaded inserts with thread size, depth, and location.
- Finishes: Production-ready finish specifications including form liner manufacturer and pattern number, sandblast depth and media type, acid etch retarder product and application area, reveal dimensions and profiles, and paint or sealer specifications with application areas.
Appropriate Uses: Shop drawing production, bar bend schedule generation, material procurement lists, production form setup, quality control checklists, piece-specific cost tracking, and direct machine control for automated production equipment. This is the primary operating level for DesignLogic's BIM-to-ERP data transfer.
LOD 500: As-Built Verification
LOD 500 represents the as-built condition, where the model has been verified against field conditions through surveying, scanning, or other measurement methods. For precast concrete, LOD 500 means that the model element dimensions, locations, and orientations have been confirmed to match the actual installed condition of the precast elements on the project site. This verification typically uses laser scanning, total station surveys, or photogrammetry to compare the as-installed geometry against the design model.
What LOD 500 Includes for Precast:
- Geometry: As-built element geometry verified through field measurement. Actual installed positions documented, including any deviations from design location.
- Reinforcement: As-fabricated reinforcement verified through QC inspection records and linked to the model. Any field modifications to reinforcement documented.
- Connections: As-installed connection conditions documented, including field weld inspections, grout placement records, and torque verification for bolted connections.
- Properties: Actual concrete test data (break strengths, unit weight measurements), material certifications, and QC test results linked to each element in the model.
Appropriate Uses: Facility management and maintenance, future renovation planning, structural assessment and load rating, insurance and warranty documentation, and regulatory compliance records. LOD 500 models serve as the permanent digital record of the built facility.
When to Use Each LOD Level
The appropriate LOD level depends on the project phase, the purpose of the model, and the contractual requirements. Many projects specify LOD requirements in the BIM Execution Plan (BEP), which should be developed at the start of the project with input from the precast producer. A common mistake is requiring LOD 400 for all elements at the start of the project, which wastes engineering resources on detail that will change as the design develops. A more practical approach is progressive LOD refinement, where elements start at LOD 200 during schematic design and are progressively developed to LOD 300, 350, and 400 as the design stabilizes.
Project Phase LOD Purpose ======================== ===== =========================== Conceptual / Feasibility 100 Massing, budget estimate Schematic Design 200 Piece count, coordination Design Development 300 Accurate takeoffs, bidding Construction Docs 350 Multi-trade coordination Shop Drawing Production 400 Fabrication, procurement Erection Complete 500 As-built record Element-Specific Progression: Wall Panels: 200 -> 300 -> 350 -> 400 (4-6 weeks per step) Double Tees: 200 -> 300 -> 400 (skip 350 for standard) Columns: 200 -> 300 -> 400 (skip 350 for standard) Connections: 200 -> 350 -> 400 (skip 300, coordinate early) Stairs: 200 -> 300 -> 400 (relatively simple geometry)
How DesignLogic Supports Progressive LOD Refinement
DesignLogic plugins are designed to work with precast models at any LOD level, extracting whatever data is available and flagging gaps that indicate opportunities for further refinement. The plugin adapts its extraction behavior based on the LOD of each element, ensuring that the data sent to CastLogic ERP is appropriate for the current project phase.
- LOD 200-300 Extraction: DesignLogic extracts piece counts, approximate dimensions, estimated weights, and material assignments. This data populates the CastLogic estimating module for budgetary pricing. The plugin marks each record as "preliminary" to prevent premature production planning.
- LOD 300-350 Extraction: DesignLogic extracts accurate dimensions, weights, volumes, preliminary reinforcement quantities, connection types, and embed counts. This data supports competitive bidding, material procurement planning, and initial production scheduling in CastLogic.
- LOD 400 Extraction: DesignLogic extracts complete fabrication data including every reinforcing bar, every embed, every finish specification, and every connection component. This data drives the full production workflow in CastLogic: shop drawing generation, bar bend schedules, material procurement, production scheduling, QC checklists, and delivery planning.
- LOD Gap Analysis: DesignLogic's model validation tool reports the effective LOD of each element based on the data it contains. If a project requires LOD 400 but some elements are still at LOD 300, the tool identifies specifically what information is missing (e.g., "WP-105: missing reinforcement detail, missing embed locations, missing finish specification on Face 2") so the engineer knows exactly what needs to be developed.
Common Pitfall: LOD Inconsistency Within a Model
One of the most common issues in precast BIM models is LOD inconsistency, where some elements in the model are at LOD 400 while others are still at LOD 200. This creates confusion about which data can be relied upon for production planning. DesignLogic's LOD Gap Analysis tool identifies these inconsistencies and generates a report showing the LOD status of every element in the model, making it easy to track progress toward the target LOD.
BIMForum LOD Specification References
The BIMForum LOD Specification is the definitive industry reference for Level of Development definitions. The specification includes element-specific LOD descriptions for precast concrete under the Concrete category, covering precast structural elements (beams, columns, walls, slabs), precast architectural elements (cladding panels, spandrels, window surrounds), and prestressed concrete elements (double tees, hollow-core planks, bridge girders).
The specification is updated annually and is available free of charge from the BIMForum website. When establishing LOD requirements for a precast project, reference the current edition of the BIMForum LOD Specification and supplement it with precast-specific requirements for reinforcement, strand patterns, embeds, and surface finishes as described in this article. Include these requirements in the project BIM Execution Plan and ensure that all stakeholders, including the architect, structural engineer, precast producer, and general contractor, agree on the LOD expectations at each project phase.
Understanding and correctly applying LOD levels is not just a modeling exercise. It is a project management tool that ensures the right level of engineering effort is invested at the right time. When combined with tools like DesignLogic that can extract and validate data at each LOD level, progressive LOD refinement becomes a practical workflow that balances engineering efficiency with production readiness, delivering models that are exactly as detailed as they need to be at every stage of the project.