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A design model is built to answer questions: does it fit, does it work, does it meet the brief? Then it meets other people, each with their own questions: the fire engineer, the estimator, the contractor's planner, the facilities team. Modelling "everything in detail" doesn't answer them; modelling the information each of them needs does.
The architect spends three weeks building door families with hinges, handles and vision panels. At the stage 3 fire review, the fire engineer asks for a schedule of fire ratings along the escape routes. Half the doors have no FireRating value, and the classification is missing, so the checker can't even find them. The review slips a fortnight.
Before stage 3, the design lead asks for the LOIN rows for doors: position, size, type, FireRating, classification, for the fire strategy review. The team models simple doors with those five things. The checker finds every door, the review takes an afternoon, and the detail comes later, when a contractor needs it.
Start from the user, not the element
LOIN starts with why, when, who and what — then defines only the information that serves it.
For every element type and milestone, the level of information need answers four questions:
| Question | Example for doors at spatial coordination |
|---|---|
| Who uses it? | Fire engineer, architect, cost consultant |
| For what decision? | Check ratings along escape routes; count and price doorsets |
| What geometry? | Position and overall size, no ironmongery |
| What data and documents? | Classification, FireRating, type reference |
LOD (level of development) numbers such as 200, 300, 400 describe how far an element's geometry and data have been developed. LOIN (level of information need, from ISO 7817 and ISO 19650) goes further: for each purpose and milestone it lists the geometry, the alphanumeric data and the documents an element needs. The LOD matrix many projects use is one way of writing it down.
The few properties that everyone uses
Most of the value in a design model comes from a handful of properties that other people filter and group by:
- a classification code (so cost, specifications and checks can find elements),
- level and zone (so the programme and the site can),
- fire rating, external or internal, load bearing (so reviewers can),
- a type reference that means the same thing on every element of that type.
Get these right on every element before adding any more detail.
You're the architect on a four-storey clinic. The next milestone is spatial coordination. The client's EIR asks for: a fire strategy review, a cost check against budget, and a space schedule for the client's clinicians.
Write one LOIN row for each of doors, internal walls and rooms (spaces): who uses it, for what, the geometry, and the data.
Key takeaways
- The level of information need says what each element must carry at each milestone: geometry, data and documents, for a stated purpose.
- More geometry isn't better. A door at stage 3 needs its size, position, fire rating and type, not its hinges.
- The few properties others filter by (classification, level, fire rating, zone) matter more than any amount of detail.
- Ask for the LOIN table before you start modelling a stage, and push back on rows with no purpose.
Your notes
Related tool
Set the level of development per element and stage, with responsibilities and information requirements.
Open LOD / LOIN Matrix →