Key Questions to Ask When Ordering interior framing metal mesh

Question: Does steel framing product need to have some approval on them or anyone can buy the production line and manufacture the studs and track according to the building codes and materials of let's say the city of Los Angeles CA? What does it take to become a manufacturer of steel framing?

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Answer: There is no specific process for becoming a manufacturer of steel framing, and there are several levels of manufacturers out there. At one end of the spectrum are the manufacturers who have bought a machine, and begin rolling material from coils or forming material on a brake press. Some of these manufacturers have no quality control program, no testing program, and sometimes buy their coils and sheets without mill certifications or test reports. On the other end of the spectrum, members of the Steel Stud Manufacturers Association (SSMA) are required to maintain an in-house quality control program, turn in annual audits, and have all of their material either mill certified or tested. Also, all material is required to be marked in accordance with the applicable building code. The marking requirements are different for different codes, but all require some form of marking.

The real question is what sort of requirements are in place in the specific jurisdiction where you are interested in installing your framing members. You mention the city of Los Angeles: they require specific research reports and verification calculations be submitted, and will issue a research report such as the one issued to SSMA (http://www.ssma.com/cola_.pdf). Other jurisdictions may require nothing other than a manufacturer's material certification, stating that the material complies with code. The American Iron and Steel Institute has developed a series of standards that have been adopted into the building code. The AISI's Standard for Cold-Formed Steel Framing - General Provisions gives a list of some of the requirements for framing members: compliance with specific ASTM standards, manufacturing tolerances, marking requirements, and corrosion protection. This is a start. From there, you should check with the specific jurisdiction to see what additional requirements are in place before framing materials may be used in a structure.

Although not a code requirement in all jurisdictions, I strongly urge you to set up a quality control program for your incoming material and manufacture, if you are considering manufacturing steel framing. Guidelines for this program are available from the International Code Council Evaluation Service at http://www.icc-es.org/Criteria/index.cfm. The Acceptance Criteria that apply to framing members are AC10 and AC46. Note that the SSMA does not provide guidelines for setting up framing operations, and in fact does not admit members unless they have already been manufacturing and selling steel framing for at least two years. There is an association for rollformers that may be able to give you additional information on equipment and manufacturing: the Fabricators & Manufacturers Association, at www.fmanet.org.

Wall Members and Systems                 Back to top

Question: Where can one find additional information regarding header design?

Answer: For addition information regarding header design, additional design information can be found by contacting the Center for Cold-Formed Steel Structures, [ protected] or the Steel Framing Alliance technical hotline, 1-800-79 STEEL.

Question: Are there specific provisions in the IBC for the anchorage of load bearing exterior and non load bearing exterior light gage metal walls to the foundation? What do you recommend?

Answer: There are not specific provisions in the International Code Council's International Building Code (IBC) for anchorage of cold-formed steel framed walls; but there are provisions in the International Residential Code (IRC) for these walls. The IRC not only has details for this connection, but references the Standard for Cold-Formed Steel Framing - Prescriptive Method (AISI ) for anchorage, which is typically anchor bolts through the bottom track at 4' on center. For non-prescriptive construction, there are several different methods for wall anchorage that are acceptable depending upon the load and the seismic zone. The most common method is powder actuated pins. Companies like Hilti and ITW Ramset have technical data on the holding power in structural steel and concrete; for the bearing in cold-formed steel, use the bolt bearing equations in chapter E of the North American Specification for the Design of Cold-Formed Steel Structures (AISI, ). These also may be used for other anchorage to concrete, such as expansion bolts, threaded anchors (such as Tapcon and Kwik-Con,) Spike anchors by Powers Rawl, and others. Recent developments in epoxy anchors have made them very popular with cold-formed steel framing; they can be installed in the exact location required, and the edge distance and spacing restrictions are less than the expansion anchors.

Question: Must an L-header extend over and be attached to each king stud if there are multiple king studs?

Answer: No. The Standard for Cold-Formed Steel Framing - Header Design only requires that the L-header lap over one bearing stud at each end.

Question: In certain applications, such as with two adjacent windows, it is desired to run one header over both openings. How would such a multi-span header be designed?

Answer: The Standard for Cold-Formed Steel Framing - Header Design applies only to single-span conditions. Multi-span headers would need to be designed in accordance with the AISI North American Specification for the Design of Steel Structural Members.

Question: How do I calculate the deflection of a header beam?

Answer: According to the Commentary on the Standard for Cold-Formed Steel Framing - Header Design, a conservative estimate of the vertical deflection of back-to-back or box headers can be based on the full moment of inertia of the two C-shape sections alone. The procedure to calculate the vertical deflection of an L-header is undefined because the L-header is an indeterminate assembly consisting of two angles, cripple studs, and track sections interconnected by self-drilling screws. However, the test results indicate that the measured deflections at an applied load that equal to the design load was less than L/240, which should be acceptable in most applications.

Question: What load combinations are appropriate for the design of a header?

Answer: The Commentary to the Standard for Cold-Formed Steel Framing - Prescriptive Method for One and Two Family Dwellings provides a detailed description of the loads, load combinations and design checks that are appropriate for headers. The appropriate load combinations are:

Question: When assembling a back-to-back or box header, must the track directly beneath the C-shaped sections face up or down?

Answer: The Standard for Cold-Formed Steel Framing - Header Design allows the track directly beneath the C-shaped sections to face either way. Typically, the track would face down when cripple studs and a head track are used to frame the opening and would face up when the opening extends to the bottom side of the header beam and no cripple studs and separate head track are needed.

Question: When using steel framing in fire rated wall systems, is the thickness of the steel the minimum, or the maximum? I understand that steel transmits heat, so I thought that the thickness shown might be the maximum.

Answer: Each type of header offers certain advantages and disadvantages; however, the relatively new L-header offers significant material, fabrication and installation savings. Due primarily to the limitations of the testing that has been performed; the Standard for Cold-Formed Steel Framing - Header Design limits L-headers to a maximum span of 16 feet. L-headers also have limited uplift capacity and, therefore, may not be suitable for certain high wind areas.

Question: Can the moment capacity of the header beam be based on a composite section of the C-shape sections plus the track above the header beam, the track beneath the header beam, and/or the cripple studs and head track beneath the header beam?

Answer: The Standard for Cold-Formed Steel Framing - Header Design requires a track section above and beneath the C-shape sections and prescribes their connection to the C-shape sections with 2 No. 8 screws at 24" on center. Intentionally, this screw spacing does not provide adequate restraint to sufficiently engage the track sections to act compositely with the C-shape sections. This would require a much closer and cost prohibitive screw spacing and would need to be designed in accordance with the AISI North American Specification for the Design of Steel Structural Members.

Question: Why doesn't the Standard for Cold-Formed Steel Framing - Prescriptive Method for One and Two Family Dwellings seem to require a check for wind uplift on back-to-back or box headers?

Answer: Within the applicability limits of the Prescriptive Method, uplift due to wind was checked and was found to never control the selection of back-to-back or box headers. Therefore, the tables only consider gravity loads.

Question: Must my header design conform to the design rules contained in the Standard for Cold-Formed Steel Framing - Header Design?

Answer: Yes. The Standard for Cold-Formed Steel Framing - Header Design has been adopted by reference in the ICC and NFPA building codes and thus is legally required when the local building code adopts the these building codes. Headers that fall outside the applicability limits of the limitations of the Header Design standard must be designed in accordance with the AISI North American Specification for the Design of Steel Structural Members.

Question: When using steel framing in fire rated wall systems, is the thickness of the steel the minimum, or the maximum? I understand that steel transmits heat, so I thought that the thickness shown might be the maximum.

Answer: The thickness shown in the UL listings is the minimum. See the info from the UL website below on cold-formed steel framing.

Question: In the UL listings for fire ratings, the thickness is given in gauge. I know that some of the tests were done many years ago, and thicknesses and tolerances may have changed. Are the thicknesses still current?

Answer: In the UL listings for fire ratings, the thickness is given in gauge. I know that some of the tests were done many years ago, and thicknesses and tolerances may have changed. Are the thicknesses still current?

Steel Studs

The dimensions and gauge of steel studs are minimums. The hourly ratings apply when the steel studs are of a heavier gauge and/or larger dimensions than specified in a Design. The superimposed load of bearings walls utilizing steel studs shall be based on the capacity of the studs as determined by the edition of the AISI Specification for the Design of Cold Formed Steel Structural Members with the December 11, Addendum.

Metal Thickness

Unless otherwise indicated in the individual designs, the following minimum metal thickness tables shall apply where a metal gauge designation is stated. Metal gauges are no longer referenced in ASTM Standards. It is still an industry practice to specify steel components by gauge. Because many of the designs contained herein refer to metal gauge the following information is to be used as a guide where field questions occur. The tables shown herein are to be used as a reference and the local Authority Having Jurisdiction shall be consulted if discrepancies exist between these tables and a local code requirement. Due to structural considerations and fire performance considerations the minimum thickness tables are different for steel deck (floor or roof), load bearing studs and non-load bearing studs.

The minimum thickness for load bearing steel studs is based upon ASTM C955-96, "Load-Bearing (Transverse and Axial) Steel Studs, Runners (Tracks) and Bracing or Bridging for Screw Application of Gypsum Panel Products and Metal Plaster Bases". The color code denoted by the ASTM Standard is also shown below. For load bearing steel studs, the minimum bare metal thickness shall be as follows:

Gauge Color Code Min ThknsBare Metal In. 20 White 0. 18 Yellow 0. 16 Green 0. 14 Orange 0.

For non-load bearing studs, the minimum thickness is based upon the gauge conversion table found in the Uniform Building Code. For non-load bearing steel studs, the minimum bare metal thickness shall be as follows.

Gauge Min ThknsBare Metal In. 25 0.018 24 0.021 22 0.027 20 0.033 18 0.044 16 0.055

For additional information on steel-framed wall and floor-ceiling assemblies, there is a searchable directory on the Steel Framing Alliance website, at www.steelframing.org. Also, for additional information on the details and limitations of these systems, go to the UL web information page on these assemblies:

Question: Can mold grow on steel studs?

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Answer: That's a good question, and one that requires a little background for the answer.

Mold requires three things to grow:

Steel does not contain any organic material, and therefore cannot support mold growth. However, if someone or something has left a residue of organic material on the steel framing, there is a chance that given the right conditions, mold could grow.

As with any framing material, the best practice is to keep the steel studs dry. Even if they get wet during construction, or there is a one-time event such as a pipe bursting in a wall, there should be no long-term problem if the cavity is dried out properly. It is persistent wetting, such as a steady plumbing or roof leak, which causes the greatest risk of supporting mold. Even then, the mold will most likely grow on organic surfaces, such as the paper facing of the gypsum board or wood framing members, rather than steel. In steel framing, when everything is clean and dry, there will be no opportunity for the mold to grow.

Note that the Steel Framing Alliance has an excellent publication on this issue: listed under the - About Steel Framing - bar on the home page, go to -Issue Papers - for a free download of the issue paper on mold.

Question: Wouldn't enamel coated steel provide better rust protection for a steel frame home rather than galvanized steel.

Answer: Enamel painted steel without a galvanized coating below does not provide a better protection. The reason is that zinc, through its sacrificial galvanic action, can "heal" cuts, scratches, and abrasions in the steel. With the rough handling that construction products receive, as well as the cutting, drilling, shearing, and fastening of members, the coating gets cut and scraped away. The galvanized coating works better than the enamel at covering areas that are cut or scratched.

Some of the very best coatings for steel products are painted over galvanized. The automotive industry has come a long way over the past 20 years in providing better coatings, and this is what they use in several applications. If for some reason the paint is cut or scratched, the zinc below the paint can help provide protection, and reduce the chance of blistering where moisture gets below the paint surface and rust progresses.

Enamel over galvanized would be a very effective coating for steel framing. However, due to the cost, not many manufacturers make such a product. There are some specialty coil coaters that will paint material to be rolled into framing members. As part of the interior exposed drum wall in the Georgia Dome, studs were galvanized, painted, and then covered with a thin sheet of protective plastic before they were rolled into the "C" shape. As installers put the framing into place, they removed the plastic. After over 10 years of exposed, in-place service, these studs (which can be seen from the seating area and playing field) are still in excellent condition.

Please see "Corrosion protection for life."

       Definitions         Back to top

Should you build your home from metal studs? What are the positives and negatives of metal stud construction? Over the past few years, we've had more and more clients ask about building their custom home from metal studs. Below we share our un-biased opinions on the positives and negatives for metal stud construction.

Positive: Rot, Mold and Termite Resistant

Metal studs will not rot, mold or attract termites unlike conventional wood framing. With conventional wood framed construction, the cost to replace and protect against these can be expensive. With metal stud construction rot, mold and termite invasion will not occur in your home. This may be particularly intriguing for families with mold allergies or respiratory problems.

Positive: Fire Resistant

The fire resistive qualities of metal stud construction are becoming more and more appealing to homeowners, especially our area of Southern California. We are plagued by wildfires and many of our clients are willing to invest in any measure to protect their homes from fires. Metal stud construction with a fire resistive sheathing will help improve the fire resistance of your home. To read more about other measures for protecting your home from wildfires check out our article here.

Positive: Less Waste if Prefabricated

We've worked with a metal stud fabrication company called B&T Manufacturing who pre-cuts, pre dimples and fabricates all of the steel members in our buildings. This requires a bit more coordination and work upfront with the engineers and fabrication team during the design process however, it can drastically reduce waste on site because each framing member is precut to size in the shop. There should be minimal to no cutting of members on site as the frame is erected, therefore minimal waste.

Positive: Ease of Installation

Metal studs are roughly 1/3 the weight of the same size wood member. This is because metal studs are 'C' shaped in section and hollow. The light weight makes it easier for the framers to carry and lift into place on site. This also means a lower volume of raw material being used.

If the metal studs were prefabricated and cut to size in a shop as discussed above, the erection of the frame will be even faster. This will reduce the time the framing crew is on site and most likely lower installation costs.

Positive: Predictable Quality, No Bowing or Warping

Compared to wood stud framing, the quality and precision of metal studs far exceeds wood members. Wood members can bow, warp, twist and have endless imperfections that can reduce structural integrity and cause problems during the lifecycle of a building. Metal studs are manufactured with a high level of precision which will significantly minimize the need to fur out walls or use plaster to float out walls or surfaces that are not plumb or level.

This impeccable precision of metal stud framing should not be overlooked. When building a custom home from wood studs, there is often a significant amount of time invested by the plaster and framing crew to shim, fur and float out walls and ceilings to correct them. If this time isn't required, that means a nice chunk of money and time saved on the project.

Negative: Insulation Values

Metal is inherently a better thermal conductor compared to wood. This doesn't mean metal studs are a poor solution, it simply means that the wall assembly made from metal studs needs to be slightly modified to reduce thermal transmittance. A common way to modify a metal stud wall to meet insulation requirements is to skin the outside of the wall with a layer of rigid insulation. The layer of rigid insulation outside the metal studs and sheathing minimizes thermal bridging and heat transfer through the wall.

This type of assembly is often referred to as an EIFS assembly. With EIFS assemblies, there is typically a higher cost involved and can be unfamiliar for traditional home builders. We personally like the EIFS system and have designed multiple buildings using this type of system.

Negative: Higher Cost

Currently, metal stud framing is now only about 30% more expensive than wood studs. The higher cost is not all in the material, it is mostly the installation costs. This upfront cost may be unattractive to building owners that are on a tight budget however it is important to evaluate potential savings throughout the life cycle of the building. For example, the owner will not be reframing the building from termite, mold or rot damage. They will not be as concerned about water or fire damage. The cost saved to replace rot, termite, mold, water or fire damage could easily offset the upfront 30% investment to go with metal studs.

Negative: Unfamiliar Among Traditional Framers

Traditional or small builders may be unfamiliar with metal stud framing. The learning curve to erect a metal stud building may impact schedule and result in errors on site. It is critical to work with a building and framing crew who has erected metal stud construction in the past as opposed to hiring a conventional wood framing crew.

Negative: Wall Hanging

Unlike wood studs, the homeowner cant simply hammer a nail into a wood stud to hang a picture, mirror or television arm. With a metal stud building, the contractor will often add wood blocking in the areas where these items may be located. This will allow the homeowner to screw or nail directly into wood using conventional nails and screws. In our opinion this is a minor drawback of metal studs and can be easily addressed with a little planning.

Negative: Wireless Signal Interference

One of the most frequent complaints about metal framed buildings is the interference with wireless signals. This can be solved relatively easily with multiple routers, wifi boosters or antenna extensions.

Negative: Not Biodegradable & Higher Embodied Energy

We are an environmentally conscious Architecture firm and the fact that metal studs are not biodegradable and have a higher embodied energy is often difficult for us to overlook. That being said, although wood is a renewable resource, there is a significant environmental price to pay to harvest trees.

One thing to note about metal stud framing is that the members are often composed of recycled content. When metal stud buildings are demolished, the metal can be recycled and used again. We have have not been able to find comprehensive studies on the environmental impacts for each of these construction types so it is difficult for us to make select on system over the other purely based on environmental impact. If these studies are available please notify us at www.rostarchitects.com.

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