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Header Design

1. The L-header seems to offer many advantages over the traditional back-to-back or box header. When am I not permitted to use an L-header?

2. 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?

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

4. 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?

5. How do I calculate the deflection of a header beam?

6. What load combinations are appropriate for the design of a header?

7. 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?

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

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

10. Where can one find additional information regarding header design?

Question No. 1:

The L-header seems to offer many advantages over the traditional back-to-back or box header. When am I not permitted to use an L-header?

Answer No. 1:

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.

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Question No. 2:

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 No. 2:

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 .

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Question No. 3:

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

Answer No. 3:

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.

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Question No. 4:

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 No. 4:

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 .

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Question No. 5:

How do I calculate the deflection of a header beam?

Answer No. 5:

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.

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Question No. 6:

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

Answer No. 6:

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:

Gravity : Uplift :

1.4D 0.9D - 1.6W

1.2D + 1.6L + 0.5(Lr or S) 1.2D + 0.5(Lr or S) + 0.5L - 1.6W

1.2D + 0.5L + 1.6(Lr or S) 1.2D + 1.6(Lr or S) - 0.8W

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Question No. 7:

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 No. 7:

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.

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Question No. 8:

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

>strong>Answer No. 8:

Yes. The Standard for Cold-Formed Steel Framing - Header Design has been adopted by reference in the 2003 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 .

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Question No. 9:

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

Answer No. 9:

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

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Question No. 10:
Where can one find additional information regarding header design?

Answer No. 10:

For addition information regarding header design, additional design information can be found by contacting the Center for Cold-Formed Steel Structures, ccfss@mst.edu, or the Cold-Formed Steel Engineers Institute, www.cfsei.org.

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