Tightening up with BIM

Stick framing is dead. The last time I saw a 2x4 on-site it was used as a strut to hold up a panelized wall system for nailing.

Rafters? What are those? We use roof trusses. Floor joists? Forget about it. We use open-web floor trusses that come precut to the site, and we have very low-cost labor follow the numbers to build the frame. Most of our guys don’t even carry hammers … just a few tools for micro-adjusting alignment and a pneumatic gun.

Now, while these statements aren’t true today, they most likely will be 10 years from now. Here’s why: BIM technology is sweeping through the residential architecture design/build community at a torrid pace. Easily 50 percent of today’s home designs are in BIM systems, and maybe even a far greater percentage than this. (The 50% figure is from a 2009 McGraw-Hill study and the number has only risen since then.)

Moreover, super-sophisticated BIM software isn’t used only by the “buy side” of the construction industry — e.g., architects, engineers and design/build firms. BIM solutions are offered, often for free, for use by the “sell-side” too, e.g. the component manufacturers (CMs) who build the trusses and wall panels. Boise Cascade recently came out with a new version of BC Framer, an advanced engineered wood product layout and engineering software. It was developed in the MiTek Sapphire platform (full disclosure: MiTek is a client of mine), and designers using BC Framer, working with CMs and their affiliated dealers, can optimize the use of engineered wood products in residential structural design on a lot-specific basis. MiTek’s Sapphire Structure software platform now offers a free BIM tool for builders, architects and engineers called Viewer, so you can collaborate with your component manufacturer, on roof trusses, walls panels and floor trusses. MiTek just acquired USP Connectors (competitor to Simpson Strong-Tie), and they will soon be issuing a connector-specifying software, linked to Sapphire and therefore to BC Framer, which includes both USP and Simpson Strong-Tie products.

In other BIM news, CG Visions has written a software called BIM Pipeline that will link BIM software like ITW’s Instinct and VisionRez directly to a home builder’s estimating system or model option database and pricing modules so he can generate lot-specific pricing on the fly as the house is optioned out.

What are the results of so much BIM power?

• Through the application of BIM and components (trusses, panels, EWP, etc.) home builders will be able to build customized homes at production speeds and double-digit margins. Builders who have the right software can do that now. See an interesting case study of Logan Homes at this link: buildermt.com/Logan%20Long-Form%20Final.pdf. Component manufacturers can stage component deliveries to the job to be assembled as a kit of parts, often by low-cost labor.

• Code-compliant thermal envelopes will be easier to construct, whether you’re building to IECC, LEED, IgCC, Energy Star Qualified Homes, or NAHB’s NGBS. You will be able to digitally prebuild green compliance into the component design using BIM, or maybe find that advanced thermal envelope already embedded in your BIM model put there as a service by a BIM provider.

• You will get tighter, higher-performing homes because, let’s face it, stick framing is wasteful and imprecise. Sometimes, framers depend on the sheathing to tighten up the structure, and the sheathers depend on the housewrappers to tighten up the sheathing, etc. Manufactured components invariably make tighter homes because the components are digitally preassembled in BIM models to make sure they fit together with tight tolerances, code compliance and proper load paths. And if you need to run ducts through conditioned spaces as many new green codes require, the duct pathways can be engineered into the floor truss at the manufacturing plant. The pathway doesn’t have to be hacked out with a recip saw — risking cuts that compromise the load-carrying ability of the framing member — by a sub who isn’t attuned to the subtleties of your structural frame.

Already roof trusses enjoy a roughly 70 percent market share in new U.S. homes, and the logic and reason for this dominance increasingly will extend to wall panels, floor joists and engineered wood products. It’s inevitable, and low-cost, pervasive BIM solutions only accelerate the transition.

So, with BIM and the increasingly engineered nature of the frame, it’s really not far-fetched, even 10 years from now, for a young framer to wander by a stack of banded 2x4s and ask, “What did you guys used to use those things for?”

 

John D. Wagner is an award-winning author of many books and articles about construction, and a frequent contributor to the industry’s leading trade magazines. A sought-after speaker for industry events, he can be contacted at JohnDWagner.com. Read past columns at ForResidentialPros.com.

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