Washington Administrative Code › Title 51 - Enterprise Services, Department of (Building Code Council) › Chapter 51-51 - State Building Code adoption and amendment of the 2021 edition of the International Residential Code › Section 51-51-4504 - Section R4504-Alterations

Current through Register Vol. 24-14, July 15, 2024
R4504.1 General.
Alterations
to
				existing buildings shall comply with the provisions of this code for new
				construction, except as permitted by this section.
R4504.2 Newly constructed elements.
Newly
				constructed elements, components, and systems shall comply with the
				requirements of this code.
EXCEPTION:
Added openable windows are not required to comply with
						  the light and ventilation requirements of Section R303.
R4504.3 Nonconformities.
The work shall not
				increase the extent of noncompliance or create nonconformity to those
				requirements that did not previously exist.
R4504.4 Structural.
Altered structural elements
				and systems shall comply with Section R102.7.1 and the structural provisions of
				this chapter. New elements shall meet all of the requirements of this code for
				new construction. Structural elements that are uncovered during the course of
				the alteration and that are found to be unsafe shall be repaired in accordance
				with Section R102.7.1.
R4504.4.1 Decreased structural capacity.
Where an
				alteration causes a decrease in capacity in any structural component, that
				structural component shall be shown to comply or shall be altered to comply
				with the applicable provisions of Chapters 3, 4, 5, 6, and 8.
R4504.4.2 Increased structural loads.
Where an
				alteration causes an increase in loads as described in this section, the
				existing structural components that support the increased load, including the
				foundation, shall be shown to comply or shall be altered to comply with the
				applicable provisions of Chapters 3, 4, 5, 6, and 8. Existing structural
				components that do not provide support for the increased loads shall not be
				required to comply with this section.
R4504.4.2.1 Dead load increase.
Dead load shall be
				considered to be increased for purposes of this section when the weight of
				materials used for the
alteration
exceeds the weight of the
				materials replaced, or when new materials or elements are added.
EXCEPTIONS:
1. Buildings in which the increase in dead load is
							 due entirely to the addition of a second layer of roof covering weighing 3
							 pounds per square foot (0.1437 kN/m2) or less over
							 an existing single layer of roof covering.
2. Installation of rooftop-mounted photovoltaic (PV)
							 panel systems weighing 4 pounds per square foot or less over an existing single
							 layer of roof covering.
R4504.4.2.2 Live load increase.
An increase in
				live load shall be determined based on Table R301.5.
R4504.4.2.3 Snow load increase.
Snow load shall be
				considered to be increased for purposes of this section when alteration of the
				roof configuration creates new areas that accumulate drifted snow.
R4504.4.2.4 Wind load increase.
Wind load shall be
				considered to be increased for purposes of this section when the surface area
				of any exterior elevation subject to wind pressure is increased by more than 5
				percent.
R4504.4.2.5 Seismic load increase.
Seismic load
				shall be considered to be increased for purposes of this section in
existing buildings
assigned to Seismic Design Category C,
				D0, D1, or
				D2 where new materials replace lighter weight materials
				in one of the following conditions:
1.
			 Concrete tile or tile roof covering of similar weight is installed on more than
			 50 percent of the total roof area.
2. Brick veneer or cladding of similar weight
			 is installed on walls above the second story.
R4504.5 Ventilation.
Reconfigured spaces intended
				for occupancy and spaces converted to habitable or occupiable space in any work
				area shall be provided with ventilation in accordance with Section R303.
R4504.6 Ceiling height.
Where a habitable attic or
				habitable space in a basement is created in an existing building, ceiling
				height shall not be less than 6 foot 8 inches (2032 mm). Bathrooms, toilet
				rooms, and laundry rooms shall have a ceiling height of not less than 6 feet 4
				inches (1931 mm).
EXCEPTIONS:
1. For rooms with sloped ceilings, the required floor
							 area of the room shall have a ceiling height of not less than 5 feet (1524 mm)
							 and not less than 50 percent of the required floor area shall have a ceiling
							 height of not less than 6 feet 8 inches (2134 mm).
2. At beams, girders, ducts, or other obstructions,
							 the ceiling height shall be not less than 6 feet 4 inches (1931 mm) from the
							 finished floor.
R4504.7 Stairways, handrails, and guards.
Stairs,
				handrails, and guards shall comply with this section.
R4504.7.1 Stairway illumination.
Stairways within
				the work area shall be provided with illumination in accordance with Section
				R303.6.
R4504.7.2 Stair width.
Existing stairs not
				otherwise being altered or modified shall be permitted to maintain their
				current clear width at, above and below existing handrails.
R4504.7.3 Stair headroom.
Headroom height on
				existing stairs being altered or modified shall not be reduced below the
				existing stairway finished headroom. Existing stairs not otherwise being
				altered shall be permitted to maintain the current finished headroom.
R4504.7.4 Stair landing.
Landings serving existing
				stairs being altered or modified shall not be reduced below the existing
				stairway landing depth and width. Existing stairs not otherwise being altered
				shall be permitted to maintain the current landing depth and width.
R4504.7.5 Stair treads and risers.
An existing
				stairway shall not be required to comply with Section R311.7.5 where the
				existing space and construction does not allow a reduction in pitch or slope.
				Where risers are added to an existing stair, the tread and riser dimensions of
				the added risers shall match the existing stair.
R4504.7.6 Handrails and guards.
Where a stair or
				any portion of a stair is reconstructed, a handrail and guard, where required,
				shall be provided in accordance with Section R311 and R312.