International Building Code Section 3403


International Building Code 3403.1

Existing buildings or structures. Additions or alterations
to any building or structure shall comply with the
requirements of the code for new construction. Additions or
alterations shall not be made to an existing building or structure
that will cause the existing building or structure to be in violation
of any provisions of this code. An existing building plus
additions shall comply with the height and area provisions of
Chapter 5. Portions of the structure not altered and not affected
by the alteration are not required to comply with the code
requirements for a new structure.

Flood hazard areas. For buildings and structures
in flood hazard areas established in Section 1612.3, any
additions, alterations or repairs that constitute substantial
improvement of the existing structure, as defined in Section
1612.2, shall comply with the flood design requirements for
new construction, and all aspects of the existing structure
shall be brought into compliance with the requirements for
new construction for flood design.

International Building Code 3403.1.1

Flood hazard areas. For buildings and structures
in flood hazard areas established in Section 1612.3, any
additions, alterations or repairs that constitute substantial
improvement of the existing structure, as defined in Section
1612.2, shall comply with the flood design requirements for
new construction, and all aspects of the existing structure
shall be brought into compliance with the requirements for
new construction for flood design.

International Building Code 3403.2

Structural. Additions or alterations to an existing
structure shall not increase the force in any structural element
by more than 5 percent, unless the increased forces on the element
are still in compliance with the code for new structures,
nor shall the strength of any structural element be decreased to
less than that required by this code for new structures. Where
repairs are made to structural elements of an existing building,
and uncovered structural elements are found to be unsound or
otherwise structurally deficient, such elements shall be made to
conform to the requirements for new structures.

Existing live load. Where an existing structure
heretofore is altered or repaired, the minimum design loads
for the structure shall be the loads applicable at the time of
erection, provided that public safety is not endangered
thereby.

Live load reduction. If the approved live load is
less than required by Section 1607, the areas designed for
the reduced live load shall be posted in with the approved
load. Placards shall be of an approved design.

Seismic. Additions, alterations or modification or
change of occupancy of existing buildings shall be in accordance
with this section for the purposes of seismic considerations.

Additions to existing buildings. An addition
that is structurally independent from an existing structure
shall be designed and constructed with the seismic
requirements for new structures. An addition that is not
2006 INTERNATIONAL BUILDING CODE. 541
structurally independent from an existing structure shall
be designed and constructed such that the entire structure
conforms to the seismic-force-resistance requirements
for new structures unless the following conditions are
satisfied:
1. The addition conforms with the requirements for
new structures,
2. The addition does not increase the seismic forces
in any structural element of the existing structure
by more than 10 percent cumulative since the original
construction, unless the element has the
capacity to resist the increased forces determined
in accordance with ASCE 7, and
3. Additions do not decrease the seismic resistance of
any structural element of the existing structure by
more than 10 percent cumulative since the original
construction, unless the element has the capacity
to resist the forces determined in accordance with
ASCE 7. If the building�s seismic base shear
capacity has been increased since the original construction,
the percent change in base shear may be
calculated relative to the increased value.

Alterations. Alterations are permitted to be
made to any structure without requiring the structure to
comply with Section 1613, provided the alterations conform
to the requirements for a new structure. Alterations
that increase the seismic force in any existing structural
element by more than 10 percent cumulative since the
original construction or decrease the design strength of
any existing structural element to resist seismic forces by
more than 5 percent cumulative since the original construction
shall not be permitted unless the entire seismic-
force-resisting system is determined to conform to
ASCE 7 for a new structure. If the building�s seismic
base shear capacity has been increased since the original
construction, the percent change in base shear may be
calculated relative to the increased value.
Exception: Alterations to existing structural elements
or additions of new structural elements that are
not required by ASCE 7 and are initiated for the purpose
of increasing the strength or stiffness of the seismic-
force-resisting system of an existing structure
need not be designed for forces conforming to ASCE
7, provided that an engineering analysis is submitted
indicating the following:
1. The design strength of existing structural elements
required to resist seismic forces is not
reduced.
2. The seismic force to required existing structural
elements is not increased beyond their design
strength.
3. New structural elements are detailed and connected
to the existing structural elements as
required by Chapter 16.
4. New or relocated nonstructural elements are
detailed and connected to existing or new structural
elements as required by Chapter 16.
5. The alterations do not create a structural irregularity
as defined in ASCE 7 ormake an existing
structural irregularity more severe.
6. The alterations do not result in the creation of an
unsafe condition.

International Building Code 3403.2.1

Existing live load. Where an existing structure
heretofore is altered or repaired, the minimum design loads
for the structure shall be the loads applicable at the time of
erection, provided that public safety is not endangered
thereby.

International Building Code 3403.2.2

Live load reduction. If the approved live load is
less than required by Section 1607, the areas designed for
the reduced live load shall be posted in with the approved
load. Placards shall be of an approved design.

International Building Code 3403.2.3

Seismic. Additions, alterations or modification or
change of occupancy of existing buildings shall be in accordance
with this section for the purposes of seismic considerations.

Additions to existing buildings. An addition
that is structurally independent from an existing structure
shall be designed and constructed with the seismic
requirements for new structures. An addition that is not
2006 INTERNATIONAL BUILDING CODE. 541
structurally independent from an existing structure shall
be designed and constructed such that the entire structure
conforms to the seismic-force-resistance requirements
for new structures unless the following conditions are
satisfied:
1. The addition conforms with the requirements for
new structures,
2. The addition does not increase the seismic forces
in any structural element of the existing structure
by more than 10 percent cumulative since the original
construction, unless the element has the
capacity to resist the increased forces determined
in accordance with ASCE 7, and
3. Additions do not decrease the seismic resistance of
any structural element of the existing structure by
more than 10 percent cumulative since the original
construction, unless the element has the capacity
to resist the forces determined in accordance with
ASCE 7. If the building�s seismic base shear
capacity has been increased since the original construction,
the percent change in base shear may be
calculated relative to the increased value.

Alterations. Alterations are permitted to be
made to any structure without requiring the structure to
comply with Section 1613, provided the alterations conform
to the requirements for a new structure. Alterations
that increase the seismic force in any existing structural
element by more than 10 percent cumulative since the
original construction or decrease the design strength of
any existing structural element to resist seismic forces by
more than 5 percent cumulative since the original construction
shall not be permitted unless the entire seismic-
force-resisting system is determined to conform to
ASCE 7 for a new structure. If the building�s seismic
base shear capacity has been increased since the original
construction, the percent change in base shear may be
calculated relative to the increased value.
Exception: Alterations to existing structural elements
or additions of new structural elements that are
not required by ASCE 7 and are initiated for the purpose
of increasing the strength or stiffness of the seismic-
force-resisting system of an existing structure
need not be designed for forces conforming to ASCE
7, provided that an engineering analysis is submitted
indicating the following:
1. The design strength of existing structural elements
required to resist seismic forces is not
reduced.
2. The seismic force to required existing structural
elements is not increased beyond their design
strength.
3. New structural elements are detailed and connected
to the existing structural elements as
required by Chapter 16.
4. New or relocated nonstructural elements are
detailed and connected to existing or new structural
elements as required by Chapter 16.
5. The alterations do not create a structural irregularity
as defined in ASCE 7 ormake an existing
structural irregularity more severe.
6. The alterations do not result in the creation of an
unsafe condition.

International Building Code 3403.2.3.1

Additions to existing buildings. An addition
that is structurally independent from an existing structure
shall be designed and constructed with the seismic
requirements for new structures. An addition that is not
2006 INTERNATIONAL BUILDING CODE. 541
structurally independent from an existing structure shall
be designed and constructed such that the entire structure
conforms to the seismic-force-resistance requirements
for new structures unless the following conditions are
satisfied:
1. The addition conforms with the requirements for
new structures,
2. The addition does not increase the seismic forces
in any structural element of the existing structure
by more than 10 percent cumulative since the original
construction, unless the element has the
capacity to resist the increased forces determined
in accordance with ASCE 7, and
3. Additions do not decrease the seismic resistance of
any structural element of the existing structure by
more than 10 percent cumulative since the original
construction, unless the element has the capacity
to resist the forces determined in accordance with
ASCE 7. If the building�s seismic base shear
capacity has been increased since the original construction,
the percent change in base shear may be
calculated relative to the increased value.

International Building Code 3403.2.3.2

Alterations. Alterations are permitted to be
made to any structure without requiring the structure to
comply with Section 1613, provided the alterations conform
to the requirements for a new structure. Alterations
that increase the seismic force in any existing structural
element by more than 10 percent cumulative since the
original construction or decrease the design strength of
any existing structural element to resist seismic forces by
more than 5 percent cumulative since the original construction
shall not be permitted unless the entire seismic-
force-resisting system is determined to conform to
ASCE 7 for a new structure. If the building�s seismic
base shear capacity has been increased since the original
construction, the percent change in base shear may be
calculated relative to the increased value.
Exception: Alterations to existing structural elements
or additions of new structural elements that are
not required by ASCE 7 and are initiated for the purpose
of increasing the strength or stiffness of the seismic-
force-resisting system of an existing structure
need not be designed for forces conforming to ASCE
7, provided that an engineering analysis is submitted
indicating the following:
1. The design strength of existing structural elements
required to resist seismic forces is not
reduced.
2. The seismic force to required existing structural
elements is not increased beyond their design
strength.
3. New structural elements are detailed and connected
to the existing structural elements as
required by Chapter 16.
4. New or relocated nonstructural elements are
detailed and connected to existing or new structural
elements as required by Chapter 16.
5. The alterations do not create a structural irregularity
as defined in ASCE 7 ormake an existing
structural irregularity more severe.
6. The alterations do not result in the creation of an
unsafe condition.

International Building Code 3403.3

Nonstructural. Nonstructural alterations or repairs to
an existing building or structure are permitted to be made of the
same materials of which the building or structure is constructed,
provided that they do not adversely affect any structural
member or the fire-resistance rating of any part of the
building or structure.

International Building Code 3403.4

Stairways. An alteration or the replacement of an existing
stairway in an existing structure shall not be required to
comply with the requirements of a new stairway as outlined in
Section 1009 where the existing space and construction will
not allow a reduction in pitch or slope.