What is Cold Formed Steel Framing?
Cold formed steel framing (also called metal studs or lightweight steel framing systems) makes the steel shapes differently than the hot rolled structural steel. The cold forming process passes steel sheets between large rollers to deform the steel, but at a lower temperature than hot rolling. The rolling process compresses and stretches the steel, hardening it in the process. Most cold rolled steel is either 33,000 psi or 50,000 psi yield strength.
The typical shapes and their sizes and attributes are shown at this website: http://www.loseke.com/lgsi.html (which has all the technical information available about cold formed steel framing). At the site listed above, you can scroll down the left menu to find the properties of C sections and Z sections.
What Should I Know about Steel Studs and Joists?
Steel studs and joists get used in conventional construction to build walls (interior, exterior, bearing, and non-bearing) as well as roofs and floors. Almost every type of structure that previously got built with wood studs and wood joists now can be built with steel studs and joists. So why would anyone change from wood?
- Cold formed steel doesn’t shrink and warp like wood, so walls tend to be straighter.
- The building code offers some advantages for using “Non-Combustible” construction (which includes steel studs and joists) rather than the “Combustible” construction of wood.
- Depending on commodity pricing, sometimes steel stud walls cost less than wood stud walls…but other times they don’t.
Did you ever think about how you learned to build wood stud walls? You probably built them on the concrete slab, then tilted them up into position. That method of building walls really moves quickly. The reason it works so well is that wood, when screwed or nailed, tends to pull together at the joints. Steel stud walls won’t work that way. When steel stud walls are pre-built in factories, hydraulic jigs press them together for welding. So steel stud walls built on the jobsite generally get built vertically, one stud at a time.
The headers used in steel stud walls often are C channels toed-in (which means facing each other to create a box). If the wall needs to be insulated, make sure to insulate any box type members as they are being built, because you obviously can’t get the insulation in afterwards. Note: this issue becomes a problem because the Insulation Contractor often isn’t on the project when the walls are being built.
What Should I Know about Steel Girts and Purlins?
Pre-Engineered buildings typically use cold formed steel girts in the walls and purlins in the roofs, spanning 20′ to 30′. If you’re building a Pre-Engineered steel building, the building manufacturer will have lots of details for how to install the girts and purlins. Make sure you have a copy of the recommended installation details on site, though, and take some time to get familiar with it.
I’ve built a few conventional steel buildings (using hot formed rolled steel members for columns and beams) and found details harder to find. So if you build this type building (often used for industrial facilities) make sure to work out the details with the Design Professional. This really is a case where asking permission is better than asking forgiveness. If the details aren’t clear, don’t assume you know what makes sense, as many different (sometimes not common sense issues) may be in play in these cases.
What Public Domain Documents are Available for Further Study?
The Cold Formed Load Bearing Steel Systems and Masonry Veneer/Steel Stud Walls Technical Instructions is mostly an engineer’s guide to design, but has some excellent details in the Appendices. The Guide is at 148 pages and officially named UFC TI 809-07, November 30, 1998.
Tricks of the Trade & Rules of Thumb for Cold Formed Steel Framing:
- Learn the names of the basic cold formed members.
- Clearly understand the cold formed steel framing connections on the project.
- Determine if any members need to be insulated prior to erection (some details can’t be insulated after they are built).
Learn more about how cold-formed steel can be applied in your upcoming projects, by contacting our team today.