Department of Building Inspection

SECTION 3403.2.2.2

SECTION 34 - EXISTING STRUCTURES

3403.2.2.2 Structural alterations. When more than 30 percent, cumulative since May 21, 1973, of the floor and roof areas of the building or structure have been or are proposed to be involved in substantial structural alteration, the building or structure shall comply with Section 3403.6. The areas to be counted towards the 30 percent shall be those areas tributary to the vertical load carrying components (joists, beams, columns, walls and other structural components) that have been or will be removed, added or altered, as well as areas such as mezzanines, penthouses, roof structures and infilled courts and shafts.

When such alterations involve only the lowest story of a wood frame building or structure and Section 3405 does not apply, only the lateral force resisting components in and below that story need comply with Section 3403.6.

COMMENT 1:

Name: Pat Buscovich, S. E.

Date: December 4, 2002

Comments/Findings:

3403.2.2.2 Structural alterations. When more than 30 percent, cumulative since May 21, 1973, of the floor and roof areas of the building or structure have been or are proposed to be involved in substantial structural alteration, the building or structure shall comply with Section 3403.6. The areas to be counted towards the 30 percent shall be those areas tributary to the vertical load carrying components (joists, beams, columns, walls and other structural components) that have been or will be removed, added or altered, as well as areas such as mezzanines, penthouses, roof structures and infilled courts and shafts.

EXCEPTIONS:

1. When such alterations involve only the lowest story of a Type V ((wood frame)) building or structure and Section 3405 does not apply, only the lateral force resisting components in and below that story need comply with Section 3403.6.

2. When such alterations involve more than 30 percent of the lowest story used as a garage of a Type V, R-3 building or structure and Section 3405 does not apply, that story need not comply with Section 3403.6. When such alterations also involve more than 30 percent of the tributary floor or roof above the lowest story of a Type V, R-3 building or structure, the lateral force resisting components of the entire building or structure need comply with Section 3403.6.

[Note: To clarify the seismic triggers when structural alterations are performed in Type V building.]

Place an X in one of the following:

Retain as is:

Update as noted:

Revise:

Delete:

X

Place an X in one of the following:

More Restrictive:

Less Restrictive:

Neither more nor less:

X

COMMENT 2:

Name: Ned Fennie, AIA

Date: December 11, 2002

Comments/Findings:

3403.2.2.2 Structural alterations. When more than 30 percent, cumulative since May 21, 1973, of the floor and roof areas of the building or structure have been or are proposed to be involved in substantial structural alteration, the building or structure shall comply with Section 3403.6. The areas to be counted towards the 30 percent shall be those areas tributary to the vertical load carrying components (joists, beams, columns, walls and other structural components) that have been or will be removed, added or altered, as well as areas such as mezzanines, penthouses, roof structures and infilled courts and shafts.

EXCEPTIONS:

1. When such alterations involve only the lowest story of a Type V ((wood frame)) building or structure and Section 3405 does not apply, only the lateral force resisting components in and below that story need comply with Section 3403.6.

2. In Type V buildings or structures of R3 occupancies where more than 30% of the lowest floor area is substantially altered and that floor is used primarily for a garage, that story is exempt from the requirements in Section 3403.6. However, where the substantial alteration includes more than 30% of the tributary floor and roof areas above the that lowest level, the lateral force resisting components of the building or structure need comply with Section 3403.6.

[Note: Editorial change of Comment No. 1]

Place an X in one of the following:

Retain as is:

Update as noted:

Revise:

Delete:

X

Place an X in one of the following:

More Restrictive:

Less Restrictive:

Neither more nor less:

X

COMMENT 3:

Name: Hanson Tom - DBI

Date: February 5, 2003

Comments/Findings:

3403.2.2.2 Structural alterations. When more than 30 percent, cumulative since May 21, 1973, of the floor and roof areas of the building or structure have been or are proposed to be involved in substantial structural alteration, the building or structure shall comply with Section 3403.6. The areas to be counted towards the 30 percent shall be those areas tributary to the vertical load carrying components (joists, beams, columns, walls and other structural components) that have been or will be removed, added or altered, as well as areas such as mezzanines, penthouses, roof structures and infilled courts and shafts.

EXCEPTIONS:

1. When such alterations involve only the lowest story of a Type V ((wood frame)) building or structure and Section 3405 does not apply, only the lateral force resisting components in and below that story need comply with Section 3403.6.

2. When such alterations involve more than 30 percent of the lowest story by removing a post or posts to create a garage of a Type V, R-3 building or structure and Section 3405 does not apply, that story need not comply with Section 3403.6.

[Note: Editorial change of Comment No. 1]

Place an X in one of the following:

Retain as is:

Update as noted:

Revise:

Delete:

X

Place an X in one of the following:

More Restrictive:

Less Restrictive:

Neither more nor less:

X

COMMENT 4:

Name: CAC Structural Subcommittee

Date: February 5, 2003

Comments/Findings:

3403.2.2.2 Structural alterations. When more than 30 percent, cumulative since May 21, 1973, of the floor and roof areas of the building or structure have been or are proposed to be involved in substantial structural alteration, the building or structure shall comply with Section 3403.6. The areas to be counted towards the 30 percent shall be those areas tributary to the vertical load carrying components (joists, beams, columns, walls and other structural components) that have been or will be removed, added or altered, as well as areas such as mezzanines, penthouses, roof structures and infilled courts and shafts.

EXCEPTIONS:

1. When such alterations involve only the lowest story of a Type V ((wood frame)) building or structure and Section 3405 does not apply, only the lateral force resisting components in and below that story need comply with Section 3403.6, or

2. When such alterations involve the lowest story by of a Type V building or structure of R3 occupancy and that floor's current and proposed use is as a garage, that level is exempt from Section 3403.2.2.2. Such alterations need not be counted as part of the cumulative total of tributary area of structural alterations.

[Note: Editorial change of Comment No. 1. To clarify the code language to facilitate permit process and provide exemptions to minor structural alterations, such as removing posts, with no loss in lateral force resisting capacity.

Recommend to be brought to full CAC committee for further action.]

Place an X in one of the following:

Retain as is:

Update as noted:

Revise:

Delete:

X

Place an X in one of the following:

More Restrictive:

Less Restrictive:

Neither more nor less:

X