The Puzzle of Steel
Today, building a house with steel framing is not quite as radical an idea as it was 10 or 20 years ago. There are more reasons to do it, there is more information available about it and steel home framing has become more acceptable in the residential market.
With more people building with steel, it has gained a greater interest from the construction industry, not only from the steel companies, but also from manufacturers of related products. These include fasteners, tools, sheathing, electrical accessories, plumbing accessories and trusses. Consequently, there are more products and tools out there for steel framing.
However, this has not gone unnoticed by the commercial steel framer. Always looking for a cheaper, easier, better and more cost-effective way to get the job done, many of the tools and accessories designed for the residential builder have ended up being successfully used in the light commercial market.
A matter of trussOne of the best examples of this is the growth of the steel truss and component industry. This market was virtually nonexistent 20 years ago. Some framers realized that they could do more with a standard C-shaped stud and started building bigger and bigger trusses out of them. Then the “Gus Truss” came on the scene and did reasonably well in certain niche markets in the West and Southwest.
This was a proprietary shape, invented by Gus Stromback, that used “C” and “hat” sections for their webs and chords. In the early ’90s, several of the big wood truss plate manufacturers decided to take a serious look at steel trusses and the industry has grown ever since. Most of these trusses aren’t going on homes; they are in schools, fire stations, assisted living facilities, gyms, apartments and hotels. Why is this the case?
Many commercial projects require non-combustible materials. Until recently, wood trusses weren’t able to meet this non-combustible requirement and fire-retardant wood trusses have been questionable in the eyes of some designers and specifiers. Therefore, on large commercial projects, the design options were structural steel, concrete or gypsum planks, or sloping bar joists. Steel trusses are typically less expensive than all of these methods, and in some cases can be used in conjunction with them.
In some cases, steel trusses are easier to handle. They are lighter than a wood truss of the same load and span capacity. They are consistent in material strength and quality, with no knots, chinks, wanes or warps. They are dimensionally stable, noncombustible and impervious to termites or other insects.
The $50 billion-plus steel-truss market that was virtually nonexistent 10 years ago is continuing to grow, and is gaining acceptance across North America. In addition, new trade organizations, such as the Light Gauge Steel Engineers Association and the Steel Truss Council of America are providing standards and design guidance to help lead the way.
Talking steelAnother outgrowth of the increased interest in residential steel is a move on the part of the industry to standardize their products. In 1998, two industry groups merged to form the Steel Stud Manufacturers Association, which quickly moved to adopt an identification system for steel studs and joists, which is now being used on all steel framing material from member manufacturers. Several major manufacturers now have these new product names listed in their catalogs, and most others should have them within the next year.
The transition has caused a small amount of confusion and, in some areas, order and distribution centers are accepting orders with either the new or old names. However, most commercial users are pleased with the new standard nomenclature, since it is easier to make an “apples to apples” comparison of material costs from various sources.
In a clinchTools and fasteners have undergone major changes, as products originally developed for the commercial framing, wood or automotive industry have been retooled and researched for the commercial market. One of the most promising of these is clinching.
Clinching has been a part of the automotive industry for years; recently, clinch tool fabricators have looked to the cold-formed steel framing market because of the similarity of the product they fasten. The clinching tools are able to make an incredibly strong connection without the use of a fastener. One part of the steel is pressed into the adjacent steel, in a button or stitch configuration. The disadvantages of this type of connection are that the tools are very expensive and bulky, and a field framer would have a difficult time lugging the tools and required compressor around on a job site. Also, if a clinch is made in the wrong place or the steel is not aligned properly, the connection has to be drilled or cut out. There is no easy way to remove the connection or pull the members back apart without destroying the metal.
The clinch tools have found a receptive home in some truss and panel shops. There, for both commercial and residential applications, where the tight tolerances and controlled conditions make it less likely that bad fastenings will be made, the clinching tools have proven faster and easier than screw or weld connections. The advantage of welding and clinching over using screws is that the connections can be made from one side of the panel without having to flip it over. Clinching beats welding because of its speed, and because the clinching process does not burn away the zinc coating, touch-up paint is not required.
My favorite new tools and fasteners for use with steel framing are staples and nails. I have been intrigued with the wide variety of applications for staples since a friend of mine had an operation and, after they were finished, they “stapled” him back together. It turns out that some of the same companies that make surgical fasteners are also looking into staples and nails for steel.
At a recent trade-related meeting, a representative from Senco fasteners showed samples using both nails and staples for the stud-to-track connection required at a typical wall stud. In addition, with special treatment of the fasteners, nails are in the works for attaching both wood trim and gypsum board to steel framing. Although these fasteners are not yet widely available, the process looks promising for both commercial and residential framers.
Ahead of the packAlthough these fasteners have some exciting potential down the road, the product that is really making an impact by speeding on job sites today is the “L” header. Developed through research and field trials, the L header is basically just a bent piece of sheet metal. However, when installed properly over a door or window opening, it can replace up to four additional pieces of custom-cut framing, for carrying load-bearing joists and trusses on a wall.
The beauty of the L header is that it can be installed after the wall or panel is already built. L header members may be used to reinforce existing or undersized headers, in single- and double-member configurations (on one or both sides of the wall). If the loads are relatively light, L headers can span up to 16 feet. The one drawback of L headers is their inability to carry high uplift loads. However, testing at the National Association of Homebuilders research center is scheduled for stronger configurations that, in theory, will handle these higher loads.
One manufacturer, Dietrich Industries, has developed an entire line of products called “Trade Ready.” These products are designed with consideration for other trades, and are supposed to make it easier to install electrical boxes, ductwork, plumbing and wiring. The Trade Ready Truss and Trade Ready Header are merely variations on designs used elsewhere in the industry. However, the Trade Ready studs and floor joists are truly remarkable; the floor joists have holes 6 1/4 inches deep at their narrowest point, allowing for 6-inch diameter plumbing lines, ducts or other assemblies to pass through them without cutting or notching. The Trade Ready studs allow standard electrical boxes to be installed with nails rather than screws, using patented, specially configured holes that allow the stud to “grip” the nails as they go in. And special clips allow wiring and plumbing to pass through the holes without harming either the conduit or the framing.
These are just some of the more notable products and tools that are filtering out of the latest push for residential steel. There are entire systems of steel manufacturing coming out of such far-flung places such as New Zealand and Switzerland, that produce stronger structures with less metal, and framing members that are easier to insulate with a lower conductivity to heat. Funding for research is relatively strong now, and NAHB, the Department of Energy, and the American Iron and Steel Institute are all working on exciting new products that should be available in the next couple of years. The most ambitious project, undertaken by the North American Steel Framing Alliance, is to develop a tool that will allow a steel framer using it with metal studs to frame as fast as a wood framer with a hammer and nails.
It’s an exciting prospect, but until then, I’ll keep my screwgun handy!
Don Allen, P.E., specializes in commercial cold-formed steel structural engineering. He has been involved in the design and construction of hundreds of commercial and residential steel-framed projects.