Module 6 - Points to Ponder

Which structural framing systems and materials are most commonly used in the United States for residences? For office buildings?

What factors explain why those dominate?

• Most U.S. residences are built with light wood framing. Single-family homes are about 9 in 10 wood-framed, and mid-rise apartments are usually wood over a concrete podium, like mine.
• Wood dominates because lumber is cheap and widely available, framing crews exist everywhere, the tools are simple, and building codes allow wood (Type III and Type V construction).
• Office buildings mostly use structural steel or reinforced concrete. Steel gives long spans and open, flexible floor plates and goes up quickly, which matters to developers. Concrete offers fire resistance, less vibration, and thinner floors, and it’s common on the West Coast. Also, offices are taller and need column-free space, which pushes them past what wood codes and spans allow.

Why did you choose your system, and what did it cost you?

• My building is four stories: a concrete ground level with three stories of light wood framing above.
• Our options were fixed: a concrete base level with either light wood or mass timber above. I chose light wood because my main goal this quarter is low embodied carbon and getting as close to net zero as possible, and light wood framing uses less material than mass timber, but cost also mattered. Additionally, the wood framing fit my plan easily because it simply replaced walls I had already laid out. The concrete level was harder: placing columns and beams around my shafts and corridors took real planning.
• It also needs to be acknowledged that I’m also giving up some acoustic performance between units compared to heavier systems. If this building were to actually be built, I would need to complete more research before saying whether I’d pick the same system.

Design teams link and share models rather than working in one file.

What are the advantages of linking?

• Linking lets each discipline own and edit its own model while still seeing everyone else’s.
• Files stay smaller and faster, and responsibility stays clear.
• In my project, linking HUNT-ARCH into HUNT-STRUCTURE meant my structural framework was built directly off the architecture, so the two stayed in sync instead of me retracing walls by hand.

What errors does linking make possible that a single model would not?

• Models can end up offset, rotated, or at the wrong elevation if their coordinates don’t match.
• A team can work from an outdated version of a linked model.
• The same element can get modeled twice, once in each file.
• None of these can happen in a single model, because there’s only one position and one version of everything.

Why is getting shared coordinates right at the start so much cheaper than fixing it later?

• I ran into this myself: my base point was set at the edge of my scope box instead of the center of my building, so I had to move it before linking. Fixing it early was a quick change.
• If I would’ve fixed it late, with every link, view, sheet, clash report, and connected file built on the wrong position, it would all have to be re-aligned and re-checked.

Not every clash is a problem.

On what basis did you classify a clash as an issue versus not an issue?

• I counted a clash as an issue if it would affect what actually gets built, including clearance problems like not leaving enough room for access or maintenance.
• Clashes that came from how the model was built, like columns embedded in walls or elements touching at joins, weren’t issues because they wouldn’t cause a problem on site.

Who should have authority to close a clash on a real project?

• The lower-priority element should move. A shaft outranks an interior wall, and structure outranks almost everything. The owner of that element should resolve it, but it should only be closed after the check is re-run and the other side agrees.
• I think the engineers on the project should have final say on feasibility and safety, and the structural engineer of record has to approve any fix that changes the structure itself.