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.