General

Problems with Metal Stud Construction

Metal stud con­struc­tion is one of the options available to archi­tects, designers and project managers con­sid­er­ing which com­mer­cial wall systems to use. However, there are potential energy effi­cien­cy, safety and per­for­mance issues that arise with metal stud construction.

Limits of Cavity Insulation

Cavity insu­la­tion in metal stud walls is of limited value, largely because of the high thermal con­duc­tiv­i­ty of the steel. Therefore, layers of exterior insu­lat­ing board and exterior EPS, XPS or Polyiso board are typically required to achieve desired R‑values.

According to the Oak Ridge National Lab­o­ra­to­ry, thermal bridging lowers the effec­tive­ness of cavity insu­la­tion by 55 percent. That means that the cost-effec­tive­ness of metal studs is offset to some degree by the need for addi­tion­al layers of insulation.

Upgraded 2015 IECC require­ments, moreover, add to the challenge presented by the thermal con­duc­tiv­i­ty of steel studs.

Hazards from Smoke and Fire

As Gregory Havel states in Fire Engi­neer­ing, Since there is not much mass to the steel studs… they are as likely as steel trusses and bar joists to be weakened quickly by heat and as prone to early collapse.” Screws used in metal stud con­struc­tion are also prone to early failure when they are stripped through over-tight­en­ing or when there is rusting.

Metal stud con­struc­tion poses chal­lenges for designers and archi­tects seeking to offer clients fire-rated designs. Although four-hour fire-rated metal stud con­struc­tion is possible, they require the addition of multiple layers of fire-resistant material.

Fire­fight­ers consider a metal stud wall assembly as a single void space because of the holes created at the factory to accom­mo­date conduit, cables and pipes. These void spaces often link to voids in the floors, which may allow smoke and fire to spread. Sprinkler systems cannot douse a fire inside these voids. Fire can also spread by breaking through the drywall that would otherwise enclose the voids.

Although the idea may be somewhat counter-intuitive, metal studs may be an even greater problem during a fire than wood studs. Havel rather ominously asserts that the heat of the fire will cause steel studs to fail more quickly than wood studs.” He further adds that if a first attack” by fire­fight­ers is unsuc­cess­ful, there might not be time for a second attack” before a struc­tur­al collapse.

Potential Electrocution Hazard

During metal stud con­struc­tion, or in the event of a fire, sharp edges pose a threat to the integrity of pro­tec­tive jackets on conduit and cabling. If the pro­tec­tive covering is com­pro­mised, the entire metal frame could be energized, posing an elec­tro­cu­tion hazard. Although short circuits often trip circuit breakers or blow fuses, this is not always the case.

Performance Compromised by Galvanic Corrosion

Metal-to-metal contact creates the potential for galvanic corrosion, the more noble metal will become the cathode and the more active metal will become the anode.”

These three con­di­tions together can lead to galvanic corrosion:

  • Direct contact between two different metals (like steel and aluminum) with varied corrosion potential
  • An elec­trolyte solution like water routinely develops, creating a con­duc­tive route between the metals.
  • A source of moisture, including wind-driven rain, con­den­sa­tion, leaks or even fog. 

Electric current flowing from one metal to the other will further increase the corrosion rate.

Ulti­mate­ly, galvanic corrosion can lead to unan­tic­i­pat­ed failures. During con­struc­tion, wood blocks are often installed between aluminum window/​door frames and gal­va­nized steel studs to prevent it; however, improper instal­la­tion can still lead to weakening caused by galvanic corrosion. Even aluminum-jacketed cables can interact with gal­va­nized steel studs if plastic bushings are not properly deployed.

Four-hour fire rated, energy-efficient Bautex Block offers a high-per­form­ing, cost-effective alter­na­tive to metal stud con­struc­tion. Click here for more infor­ma­tion about how The Bautex System can meet your project requirements.