Many BIM tender documents in Vietnam contain a familiar line: "the model shall reach LOD 400". Contractors read it and either panic (thinking every bolt has to be modelled) or ignore it (since nobody checks). Both reactions come from misunderstanding what LOD in BIM means — and the misunderstanding costs real money on both sides.
This article explains where LOD comes from, describes each of LOD 100, 200, 300, 350, 400 and 500 on the same concrete column, then shows how LOD is used in contracts in Vietnam and clears up the most common confusion: LOD is not geometric detail.
What LOD is, and who defines it
LOD stands for Level of Development — how far an element in a BIM model has developed: how certain and reliable its geometry and information are, and therefore what other people may use it for. The concept was introduced by the American Institute of Architects (AIA) in its BIM contract documents in 2008; the current version is AIA document E201-2022. BIMForum expanded it into the LOD Specification, updated annually (the latest is 2024), which describes each level for each type of element.
The core point, and the one most often missed: LOD describes how reliable the information is, not how much detail is drawn. An element at LOD 300 means its size, location and quantity are accurate enough for others to measure and coordinate from — even if it is modelled as a plain box.
Three terms are easily confused:
- LOD – Level of Development (US): the level of development, covering both geometry and information, attached to each element.
- LoD – Level of Detail (UK, formerly): geometric detail only, paired with LOI – Level of Information for non-geometric information.
- Level of Information Need (ISO 19650, detailed in ISO 7817-1:2024): the appointing and appointed parties agree the geometry, information and documentation needed for each purpose. BIMForum states that the two frameworks are complementary, not interchangeable: LOD defines the geometric part within the wider framework of level of information need.
In Vietnam, the Ministry of Construction's general BIM guidance (issued with Decision 348/QD-BXD) uses the term "level of information development (LOD)", cites the BIMForum specification, and states a key principle: LOD is not specified for the whole model, only for each model component. The national standards TCVN 14177:2024 (adopted from ISO 19650) use the level-of-information-need framework. Before arguing about a document, establish which meaning it uses — reading the two frameworks side by side is part of the Institute's BIM Manager course.
Each LOD on one concrete column
The levels below follow the BIMForum 2024 specification. The requirements of each level include those of the lower levels — except LOD 500, discussed separately.
LOD 100 — a symbol, a mass, or information only
The element is represented by a symbol or a generic representation that does not satisfy the requirements of LOD 200; information about it (cost per square metre, tonnage of equipment) may be derived from other elements. BIMForum stresses that LOD 100 elements are not necessarily geometric — they may be information attached to a floor mass. The column does not exist yet: there is only a floor mass with an area, a height and a note saying "reinforced concrete frame". Used for early cost estimates per square metre and for comparing options at concept stage.
LOD 200 — an approximate box
The element is represented generically with approximate quantity, size, shape, location and orientation; it is recognisable as a column, a pump or a light fitting, but any information derived from it must be treated as approximate. The column is a box with a placeholder section, placed roughly on the grid. Used for space planning, structural option checks and rough estimates at basic design.
LOD 300 — exact size and location; measurable
The element as designed is represented so that its quantity, size, shape, location and orientation can be measured directly from the model; enough to convey the full design intent. The column has the correct section, position and level, with its concrete grade attached. This is the level for quantity take-off, estimating and technical design drawings. BIMForum notes that designers rarely model beyond LOD 300, because the next levels require construction knowledge.
LOD 350 — plus interfaces with other elements
LOD 300 plus the interfaces with adjacent or dependent elements: connections, anchorage zones, clearances needed for construction. BIMForum added this level because LOD 300 is not enough for construction-level coordination while LOD 400 comes too early. The column carries the anchorage of its bars into the beam, the detail of its connection to the footing, and clearance for formwork. This is the level for reliable clash detection between disciplines — the central work of the Institute's BIM Coordinator course.
LOD 400 — detailed enough to fabricate and install
The element is represented with detail sufficient for fabrication, assembly and installation — the equivalent of shop drawings. The column has all its longitudinal bars, stirrups, lap lengths and cast-in items. BIMForum says plainly that most models contain few LOD 400 elements, because only items that need shop drawings are modelled to this level. Taking a column from LOD 300 to 400 with reinforcement is the practical part of the Revit Structure course.
LOD 500 — as built, field-verified
The element is a representation of the existing or as-constructed condition, established by observation, field verification or interpolation; the accuracy must be recorded with it. BIMForum is explicit: LOD 500 is not "higher" than LOD 400. It only signals that the geometry was determined by observing an existing object rather than designing a future one, which is why LOD 500 sits outside the cumulative chain of the levels above. The column as it actually stands after construction, with its acceptance records. Used for as-built records, operations and maintenance.
| Level | What it can be used for | Typical stage |
|---|---|---|
| LOD 100 | Cost per m² of floor, option comparison | Concept, preliminary design |
| LOD 200 | Space planning, rough estimates | Basic design |
| LOD 300 | Take-off, estimating, technical design drawings | Technical design |
| LOD 350 | Multi-discipline coordination, clash detection | Construction drawings |
| LOD 400 | Shop drawings, bar schedules, detailed 4D | Construction, fabrication |
| LOD 500 | As-built records, operations, maintenance | Completion, handover |
Two important observations. LOD rises element by element, not model by model: in the same technical design model a column may be at LOD 300 and a handrail at LOD 200 — because nothing more is needed yet. "An LOD 300 model" is shorthand; properly there should be an LOD table by element type. And "an LOD 500 as-built model" meaning "very detailed" is a misuse, as explained above.
LOD in BIM contracts in Vietnam
Under the rules now in force (Decree 217/2026/ND-CP, effective 1 July 2026), the BIM file is part of the design documents and the completion documents. "What level must the submitted model reach" is therefore a contract question, and LOD is the tool for answering it. The correct use in contracts and in the BIM Execution Plan (BEP):
- Build an LOD table by element and stage (a Model Element Table). Each element type — foundations, columns, beams, slabs, walls, doors, pipes, equipment — gets a level at each stage, with the responsible party named.
- Tie LOD to purpose. Does the client need the model for take-off, coordination, construction or operations? Purpose decides the LOD; LOD has no value on its own.
- State the non-geometric information that goes with each level (material grade, manufacturer, item code); if using the UK framework, state the LOD–LOI pair.
- Agree how it will be checked: who checks, with which tool, when. Without this step, LOD in a contract is just words.
The most common contract error our lecturers meet when consulting: demanding "LOD 400 for the whole model at technical design". That is impossible (the design has not settled fabrication details), useless (the client does not need it yet) and expensive (consultants price to the requirement). A sensible LOD table for this stage sits mostly at 300, with some elements at 350 for coordination. This is a core topic of the Institute's BIM Manager course, because whoever writes the BEP and the information requirements decides whether LOD is used well or badly for the whole project; What is a BEP? describes that document.
The common confusion between LOD and geometric detail
A manufacturer's Family with every thread and logo is not LOD 400. It is merely detailed geometry. If its size and position in the model have not been decided, it is still LOD 200 — with the file size of LOD 400. What is a Family in Revit? covers the consequences of such Families.
Conversely, a plain box can be LOD 300, provided its size, position and quantity are correct and measurable.
A higher LOD is not always better. An LOD 400 model at basic design is wasteful and misleading: viewers assume everything has been decided. Each stage has its appropriate LOD; exceeding it is as much an error as falling short.
LOD does not replace quality checking. A model labelled "LOD 350" in which a column sits 5 cm off grid is not LOD 350. LOD is the commitment; checking the model is the evidence — which is the BIM Coordinator's job, see What is a BIM Manager? The role, the pay and the career path.
A quick way to remember it: LOD answers "how far can it be trusted", not "how finely is it drawn".
Frequently asked questions
What is the difference between LOD 300 and LOD 350?
LOD 350 is LOD 300 plus the interfaces with other elements — connections, junction details, required clearances — for reliable construction coordination. BIMForum added it because LOD 300 is not enough for clash detection while LOD 400 comes too early.
What LOD does a design submitted for appraisal under Decision 258 need?
The decision sets no number; the level is fixed by the client's requirements and the contract. Common practice is LOD 300 (some elements at 350) for technical design and construction drawings; the completion documents need a model updated to the as-built condition.
Do LOD and LOI have to go together?
In the UK framework, yes: LOD (geometry) and LOI (information) are specified separately for each element. In the US framework, information is inside the LOD definition but should be stated explicitly. Under ISO 19650 and ISO 7817-1 both are combined in the "level of information need".
Are there tools that check whether a model meets an LOD?
There are rule-based model checkers that cover the information and part of the geometry; the rest still needs a competent person looking at the model. That is why the BIM Coordinator role exists.