Advanced Framing

Not that long ago, the term “advanced framing” meant merely using roof trusses, floor trusses and wall panels. Today, with the push for energy efficiency and green building, builders and homeowners are looking for affordable answers to some complex framing questions. Creative and innovative framing ideas are, and will continue to be, developed by companies searching for that competitive edge in the market. In this Technical Q&A, we take a look at some of the directions where advanced framing may lead the industry.

Question

Where is the structural building components industry heading in terms of advanced framing?

Answer

The structural building components industry continually looks for new and better ways to build components and provide a better quality product for framers in the field. One obstacle the industry has fought against ever since its infancy is the traditional-methods mindset, the idea that, “We have always done it that way….” Likewise, this type of mindset looks at new innovations and responds, “That looks different; it can’t possibly have the same level of performance and quality as the old way of doing things.”

When looking at innovation, it’s important to ask what constitutes quality inside the demands of innovation. Is it using more wood? More truss plates? More steel load path connectors? While everyone has their own answers to these questions, here are some basics on which most people can agree. Quality components should:

• Maximize product capacities and resistance through the use of products and connections that are easy to install. Connections should efficiently transfer loads, and it should be easy to understand how loads are transferred with respect to the interactions with other components.
• Use framing materials that are held to a high standard of reliability and that perform at or better than their listed design values.
• Optimize raw material, framing interactions and usage to gain maximum engineering efficiency—also known as engineering economics—providing the best economic solution for the structure. 
• Reduce field labor or provide the framer with an “easy button.”

In many cases, innovation and optimization go hand in hand. Here are some areas of the component industry that marry these two concepts.

Trusses

Since the development of truss design software, the industry has optimized design programs through testing and calculations to take as much material and labor out of each truss as possible. Layout and engineering software aim to ensure the proper truss-to-truss loading, load path, and, ultimately, the most optimal design. While software remains one of the main innovative activities in the truss industry, there are other areas of truss manufacturing that could also benefit from innovation.

For example, using composite lumber for truss chords is one popular option that may lead the next wave of advanced framing. The production of composite lumber includes far greater quality control than the production of conventional lumber, longer available lengths exist, and, in many cases, composite lumber is produced from a smaller diameter log to produce the end product. Some plants already use finger joint floor truss chords to increase span capacities by removing the bottom chord plated splice.

Some plants also take advantage of 2x3 lumber, but for many, 2x3s are viewed as poor quality or cheap. In other industries, getting something to perform by using 25 percent less material is considered an innovation or advanced engineering. For example, the manufactured housing industry uses 2x3s, and each structure undergoes testing through cyclic and vibrating loads applied during the drive to the jobsite.

For years, 2x3s have not been considered for component manufacturing because 2x4s were readily available and 2x3s were not. Innovating with raw materials means putting the right sized material in the right place to do the job of an equivalent 2x4 truss. As an example, if the chord and web member combined stress indices (CSIs) for a 2x3 truss are less than 0.40, why not take advantage of the savings? There is a possibility for margin increases, while at the same time providing a more competitive price to the customer. Innovations like this could make trusses more cost competitive with stick framing based on price alone. Add to this simplicity of installation and labor savings, and trusses and wall panels are positioned as the best economic solution and, therefore, the future of framing.

Another item that may be a ways off but could be a good fit for the SBC industry is fiber reinforced material. Fiber reinforced products have been used with wood for many years and increase the tension capacity in lumber drastically. While fiber reinforcement has not yet been used in trusses, as the industry looks at longer spans or shallower depths in trusses where the designs require higher tension members, this could be a key to optimizing truss performance economics. Combining fiber reinforcement with finger jointed lumber could be a win for both the lumber and component industries because it could provide for the use of a lower-grade material and yet provide a straighter end product with extremely high tension capacities. While there is a lot to overcome due to the cost of fiber reinforcement material and the manufacturing process, there is no denying the capabilities of carbon fiber, which are commonly used in both the aircraft and auto industries.

Walls

One of the innovative ideas that has impacted wall panel manufacturing that hasn’t fully taken off yet is in-line framing, another example of how a traditional stick-framing mentality is hard to overcome in the housing/framing industry. In-line framing simply lines up the trusses and rafters over the studs, placing the wall studs where they are the most effective. Where allowed by the building code and the Engineer of Record, in-line framing can be effective on two fronts: material efficiency and energy efficiency. Today’s software has the ability to view and design components in 3-D, which makes in-line framing easier to implement. With in-line framing methods and stacking the trusses and joists, CMs can remove both studs and plate material, while maximizing the capacities of the stud. This can also allow CMs to spread the stud spacing out to 24", in some cases allowing for better insulation methods.

Headers, along with window and door bucks, also present opportunities for material usage and structural resistance optimization. As we push toward more energy efficient exterior sheathing, with a wide variety of structural resistance properties, wall components may need to resist loads that traditionally have been resisted by the exterior sheathing. Trussed window and door bucks may be the solution because they can easily be engineered to resist lateral loads, which allows for exterior sheathing solutions from a far more flexible range of alternative sheathing products.

One thing to note on wall panel technology—the industry currently designs panels using software that takes traditional methods and manages material, but the software does not analyze the loads or connection methods for the members. As we continue to move toward 3-D design and engineering, we will start to calculate the load path from all applied loads onto all structural resistance elements from any direction. This assuredly will help load path resistance optimization.

No matter what direction the industry takes with advanced framing, the better we understand raw material and structural element capacities, the better the industry will be poised for increased engineering sophistication and continual improvements.