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Do light-frame wood columns that are located entirely within fire-resistance-rated walls also require individual fire protection or encasement?

Section 704.2 of the 2012 International Building Code (IBC) requires that columns which are part of the primary structural frame be individually encased for fire resistance protection.

704.2 Column protection.
Where columns are required to have protection to be fire-resistance rated, the entire column shall be provided individual encasement protection by protecting it on all sides for the full column length, including connections to other structural members, with materials having the required fire-resistance rating. Where the column extends through a ceiling, the encasement protection shall be continuous from the top of the foundation or floor/ceiling assembly below through the ceiling space to the top of the column. 

It is not uncommon for light-frame wood columns, whether they are solid or built-up, to be embedded in light-frame walls (bearing or non-bearing). In many instances, these walls are required to be rated for fire resistance per IBC Table 601 or because they are serving as a fire barrier, fire partition or fire wall. Some interpret section 704.2 as meaning that, even in this situation, light-frame wood columns would need individual fire protection (their own gypsum wrap or charred wood calculations). However, the American Wood Council has stated that these provisions are not typically applied to wood construction, especially light-frame construction. For example, as described in IBC Section 704.4, secondary members in light-frame construction which are part of a load-bearing wall (e.g., king studs) may be protected by the wall’s fire protection membrane and do not need individual encasement.

A distinction is sometimes made when a wood column supporting multiple levels of load is located in a light-frame wall. In this case, some jurisdictions may request individual protection. However, the general consensus in the wood industry is that individual column protection is not necessary under such conditions. This has been reinforced by subsequent modifications to Sections 704.2 and 704.4. It is generally understood that light-frame construction does not, by definition, have a primary structural frame and thus light-frame elements located within light-frame walls do not require individual fire protection. This position is corroborated by the fact that light-frame construction is specifically addressed in 704.4.1 as a clarification to 704.4.

704.4 Protection of secondary members.
Secondary members that are required to have a fire-resistance rating shall be protected by individual encasement protection, by the membrane or ceiling of a horizontal assembly in accordance with Section 711, or by a combination of both. 

704.4.1 Light-frame construction.
King studs and boundary elements that are integral elements in load-bearing walls of light-frame construction shall be permitted to have required fire-resistance ratings provided by the membrane protection provided for the load-bearing wall.

The 2012 IBC section covering this topic was slightly revised in the 2015 IBC, which reads as follows.

704.2 Column protection.
Where columns are required to have protection to achieve a fire-resistance rating, the entire column shall be provided individual encasement protection by protecting it on all sides for the full column height, including connections to other structural members, with materials having the required fire-resistance rating. Where the column extends through a ceiling, the encasement protection shall be continuous from the top of the foundation or floor/ceiling assembly below through the ceiling space to the top of the column.

However, a code change proposal FS7-15 for the 2018 IBC addressing sections 704.2 and 704.4.1 has been approved as modified by the committee. In the 2018 IBC, these code sections will be modified to read as follows:

704.2 Column protection.
Where columns are required to have protection to achieve a fire-resistance rating, the entire column shall be provided individual encasement protection by protecting it on all sides for the full column height, including connections to other structural members, with materials having the required fire-resistance rating. Where the column extends through a ceiling, the encasement protection shall be continuous from the top of the foundation or floor/ceiling assembly below through the ceiling space to the top of the column.
Exception: Columns that meet the limitations of Section 704.4.1.

704.4.1 Light-frame construction.
Studs, columns, and boundary elements that are integral elements in walls of light-frame construction, and are located entirely between the top and bottom plates or tracks shall be permitted to have required fire-resistance ratings provided by the membrane protection provided for the wall.

The committee’s reasoning behind the acceptance of these changes provides further clarification:

Committee Reason: The committee agreed that built-up solid structural elements, such as two or more vertical framing members, within fire-resistance-rated walls of light-frame construction that meet the limitations of Section 704.4.1, can be part of a fire-resistance-rated wall assembly without requiring the individual encasement protection of Section 704.2.

The East Bay ICC Tri-Chapter Uniform Code Committee in California recently published a guideline on this topic that matches the wood industry’s consensus as outlined above. The guideline, available in its entirety here, proposes the following policy:

“Studs, boundary elements, posts, multiple stud groups, built-up columns and solid columns that are framed within the wall and do not penetrate the top or bottom plates are all designed to the same criteria and shall be considered integral elements. These elements that are integral within the confines of the load bearing wall, and do not penetrate the top or bottom plates, shall be permitted to be protected in light frame construction by the membrane protection of the fire resistance rated bearing wall.”

In summary, the wood industry as well as code committees, jurisdictions and building code changes are recognizing that the individual column encasement requirements of IBC Section 704.2 are not generally applied to light-frame wood columns located fully within a fire-resistance-rated wall assembly. The final decision is ultimately up to the local building official or Authority Having Jurisdiction until the above mentioned code changes take effect with future code editions. If a jurisdiction does require individual column protection, an alternative to protecting the column with gypsum would be to calculate its fire resistance rating using the char calculations contained in Chapter 16 of the American Wood Council’s National Design Specification® (NDS®) for Wood Construction. The use of these calculations for fire resistance of exposed wood members is permitted in IBC Section 722.1. For more information regarding fire-resistance ratings of wood members, click here.