Once the team knows what it is optimizing for, the design moves into a building information model (BIM), and the model matures in steps. Naming those steps keeps everyone honest about what is decided and what is not. The industry uses five Levels of Development (LOD), a framework the American Institute of Architects introduced in 2008.
- LOD 100. Masses and symbols. For a mass timber home: walls are thick vertical blocks, roofs are slabs laid across them.
- LOD 200. Approximate quantity, size, shape, and location. Rafters appear; wall and roof build-ups take shape.
- LOD 300. Exact dimensions and positions. Rafters are sized and spaced by the engineer; wall panels are cut to their real size for manufacturing and shipping.
- LOD 400. How each element is built. Screw locations, bracket sizes, slots, and wood-to-wood joints are detailed.
- LOD 500. The model represents the real building. Individual timber elements are exported to machine code for fabrication.
When we say bring us in early, this is what we mean: the earlier mass timber is part of the model, the fewer decisions have to be unwound at LOD 300 and 400, where changes are expensive. One of the most common late surprises is waste, and it deserves its own look.
Adapted with permission from a note by our colleagues at Red Falls Timber Co.
