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Chapter 10-5.5: Residential Building Code 1

10-5.5-1.  Legislative Intent. Go to the top

The purpose of this chapter is to protect the public health, safety, and general welfare by regulating the construction, alteration, movement, enlargement, replacement, repair, equipment, use and occupancy, location, removal, and demolition of detached one- and two-family dwellings and townhouses, not more than three stories above grade in height with a separate means of egress, and their accessory structures. The city council hereby adopts the 2012 edition of the International Residential Code with certain amendments thereto found to be in the best interests of the city.

Ordinance Nos. 7566 (2007); 7925 (2013)

10-5.5-2.  Adoption of the International Residential Code With Modifications. Go to the top

(a)  The 2012 edition of the International Residential Code of the International Code Council is hereby adopted by reference as the City of Boulder Residential Building Code and has the same force and effect as though fully set forth in this chapter, except as specifically amended by the provisions of this chapter.

(b)  The Appendix chapters D, E, G, H, J, K and P and sections contained therein are adopted.

(c)  Section R101.1, "Title," is repealed and reenacted to read:

R101.1 Title. These provisions shall be known as the Residential Code of the City of Boulder or residential code and shall be cited as such and will be referred to herein as "this code".

(d)  Sections R102 through R114 are repealed. This code shall be administered in accordance with chapter 1, "Administration," of the International Building Code as adopted, with amendments, by Section 10-5-2, "Adoption of International Building Code With Modifications," B.R.C. 1981.

(e)  The following definitions are added to Section R202, "Definitions":

NEW DWELLING UNIT. A dwelling unit is considered to be a new dwelling unit when the entire structure is newly built and when the dwelling unit is built on top of an existing foundation, such as caissons, footings, and other foundation systems, that remains from a demolished structure.

STORAGE ROOMS OR SPACES. Storage rooms or spaces are rooms or spaces with a level of finish sufficient only to make the room usable for the intended storage purposes. Rooms or areas that exceed these minimums will be considered habitable space and will have to meet the code requirements applicable to habitable space.

(f)  A new sentence is added to the end of Section R301.1, "Application," stating:

Structural calculations demonstrating how the proposed construction meets the applicable requirements for load supports must be provided to the building official.

(g)  The climatic and geographic design criteria applicable to Table R301.2.1 are:

Ground Snow Load = thirty pounds per square foot with a minimum Roof Snow Load of 30 pounds per square foot.

Three-second wind gust velocity = 120 mph east of Broadway, 130 mph west of Broadway

Seismic Design Category = B

Weathering = severe

Frost line depth = 32 inches

Termite = slight

Decay = none to slight

Winter Design Temp = 2 degrees Fahrenheit

Ice barrier underlayment required = NO

Flood Hazards = See Sections 9-3-3 through 9-3-9, B.R.C. 1981

Air freezing index = 459

Mean annual temp = 52.1

(h)  Section R301.2.4, "Floodplain construction": A new sentence is added to the end of the section reading "All work on structures in the scope of this code shall also meet the requirements of Sections 9-3-3 through 9-3-9, B.R.C 1981."

(i)  The exception listed in Section R302.2, "Townhouses," is repealed and reenacted to read:

Exception: A common 1-hour fire-resistance-rated wall assembly tested in accordance with ASTME 119 or UL 263 is permitted for townhouses equipped throughout with an automatic sprinkler system installed in accordance with the requirements of section P2904 if such walls do not contain plumbing or mechanical equipment, ducts, or vents in the cavity of the common wall. The wall shall be rated for fire exposure from both sides and shall extend to and be tight against exterior walls and the underside of the roof sheathing. Electrical installations shall be installed in accordance with chapters 34 through 41 and chapter 43. Penetrations of electrical outlet boxes shall be in accordance with section R302.4. For townhouses not equipped throughout with an automatic sprinkler system installed in accordance with the requirements of section P2904, a common 2-hour fire-resistance-rated wall is permitted if such walls do not contain plumbing or mechanical equipment, ducts or vents in the cavity of the common wall. Electrical installations shall be installed in accordance with chapters 34 through 41 and chapter 43. Penetrations of electrical outlet boxes shall be in accordance with section R302.4.

(j)  The first sentence of the Exception to Item 2 in Section R302.2.2, "Parapets," is amended by deleting "a minimum class C roof covering" and replacing it with "a minimum Class B roof covering."

(k)  Section R302.5.1, "Opening protection," is repealed and reenacted to read:

R302.5.1 Opening protection. Openings from a garage directly into a room used for sleeping purposes shall not be permitted. Other openings between the garage and residence shall be equipped with weather-stripped, solid wood doors not less than 1 and 3/8 inches (35 mm) in thickness, solid or honeycomb-core steel doors not less than 1 and 3/8 inches (35 mm) in thickness, or 20-minute fire-rated doors, equipped with a self-closing device.

(l)  Section R309.5, "Fire sprinklers," is deleted.

(m)  Section R311.2, "Egress doors," is repealed and reenacted to read:

R311.2 Egress doors. At least one egress door shall be provided for each dwelling unit. The egress door shall be side hinged, and shall provide a minimum clear width of 32 inches (813 mm) when measured between the face of the door and the stop, with the door open 90 degrees (1.57 rad). The minimum clear height of the door opening shall not be less than 78 inches (1981 mm) in height measured from the top of the threshold to the bottom of the stop.

(n)  The following sentences are added to the end of Section R311.7.5.1, "Risers":

Where the bottom or top riser adjoins a sloping public way, walkway, or driveway having an established grade and serving as a landing, the bottom or top riser is permitted to be reduced along the slope, with the variation in height of the bottom or top riser not to exceed one unit vertical in 12 units horizontal (8-percent slope) of stairway width. The nosings or leading edges of treads at such non-uniform height risers shall have a distinctive marking stripe, different from any other nosing marking provided on the stair flight. The distinctive marking stripe shall be visible in descent of the stair and shall have a slip-resistant surface. Marking stripes shall have a width of at least 1 inch (25 mm) but not more than 2 inches (51 mm).

(o)  A new section R311.9, "Access to exterior balconies, porches, decks, and other walking surfaces from the interior of the building," is added, reading as follows:

R311.9 Access to exterior balconies, porches, decks, and other walking surfaces from the interior of the building. Access to exterior balconies, porches, decks, and other walking surfaces from the interior of the building shall be through a side-hinged or sliding glass door and shall provide a minimum clear width of 24 inches (610 mm), when measured between the face of the door and the stop, when the door, other than the sliding glass door, is open 90 degrees (1.57 rad). The minimum clear height of the door opening shall not be less than 78 inches (1981 mm) in height, measured from the top of the threshold to the bottom of the stop. Access to exterior balconies, porches, decks, and other walking surfaces from the interior of the building for the required egress door shall meet the provisions of section 311.2 for required height and width.

(p)  Section R313.1, "Townhouse automatic fire sprinkler systems," is repealed and reenacted to read:

R313.1 Townhouse automatic fire sprinkler systems. Automatic fire sprinkler systems shall be installed in townhouses in accordance with the requirements of section 903.2.8 of the City of Boulder Fire Code.

(q)  Section R313.2, "One- and two-family dwelling automatic fire sprinkler systems," is repealed and reenacted to read:

R313.2 One- and two-family dwelling automatic fire sprinkler systems. Automatic sprinkler systems shall be installed in one- and two-family dwellings in accordance with the requirements of section 903.2.8 of the City of Boulder Fire Code.

(r)  Section R315.1, "Carbon monoxide alarms," is repealed and reenacted to read:

R315.1 Carbon monoxide alarms. For new construction, an approved carbon monoxide alarm shall be installed outside each sleeping area in the immediate vicinity of bedrooms in dwelling units within which fuel-fired appliances are installed and in dwelling units and accessory structures containing habitable space that have attached garages. All carbon monoxide alarms shall be installed so as to meet the requirements of Section R315, Carbon monoxide alarms, and of the applicable provisions of §§ 38-45-101 through 106, C.R.S. Where the provisions of this code and the C.R.S. are in conflict, the most restrictive shall govern. Where there is a conflict between a general requirement and a specific requirement, the specific requirement shall be applicable.

(s)  Section R322, "Flood resistant construction," is repealed and reenacted to read:

R322 Flood resistant construction. Buildings and structures constructed in whole or in part in the floodplain must be designed and constructed in accordance with the floodplain regulations of Title 9, Land Use Code, B.R.C. 1981.

(t)  The first paragraph of Section R401.1, "Application," is repealed and reenacted to read:

R401.1 Application. The provisions of this chapter shall control the design and construction of the foundation and foundation spaces for all buildings. In addition to the provisions of this chapter, the design and construction of foundations in a floodplain as established in Title 9, Land Use Code, B.R.C. 1981, shall meet all applicable provisions of Title 9, Land Use Code, B.R.C. 1981. Where, in any specific case, the provisions of this code and the B.R.C. are in conflict, the most restrictive shall govern. Where there is a conflict between a general requirement and a specific requirement, the specific requirement shall be applicable. Wood foundations shall be designed and installed in accordance with AF&PA PWF.

(u)  A new Section R401.5, "Placement of backfill," is added to read:

R401.5 Placement of backfill. The provisions of section 1804.2 of the Building Code of the City of Boulder shall apply to the placement of backfill.

(v)  Section R408.7, "Flood resistance," is repealed and reenacted to read:

R408.7 Flood resistance. Buildings located in a floodplain as established in Title 9, Land Use Code, B.R.C. 1981, shall comply with the applicable provisions in Title 9, Land Use Code, B.R.C. 1981.

(w)  Exception 1 in Section R703.2, "Water-resistive barrier," is repealed and reenacted to read:

Exception 1: In detached accessory buildings which are not intended to be conditioned and where the interior wall cavities will remain exposed and unfilled.

(x)  Exception 3 of Section R806.5, "Unvented attic and unvented enclosed rafter assemblies," is deleted.

(y)  Section R902.1, "Roof covering materials," is repealed and reenacted to read:

R902.1 Roof covering materials. All roof covering materials shall be listed as Class A as tested in accordance with UL Standard 790 or ASTM Standard E 108. Roof assemblies with covering of brick, masonry, slate, clay, or concrete roof tile, exposed concrete roof deck, ferrous or copper shingles or sheets, and metal sheets and shingles, shall be considered Class A roof coverings. Unless otherwise specified in this section, roof coverings shall be installed to resist the component and cladding loads specified in table R301.2(2), adjusted for height and exposure in accordance with table R301.2(3).

(z)  Section R905.7, "Wood shingles," is repealed and reenacted to read:

R905.7 Wood shingles. Wood shakes, wood shingles, and wood roof covering materials are prohibited except as provided in Section 10-5-5, "Wood Roof Covering Materials Prohibited," B.R.C. 1981, for certain minimal repairs.

(aa)  Section R905.8, "Wood shakes," is repealed and reenacted to read:

R905.8 Wood shakes. Wood shakes, wood shingles, and wood roof covering materials are prohibited except as provided in Section 10-5-5, "Wood Roof Covering Materials Prohibited," B.R.C. 1981, for certain minimal repairs.

(bb)  Chapter 11, "Energy Efficiency." Sections N1101 through N1105 are repealed. A new Section N1101 is added to read:

N1101 Scope. Regulations concerning the design and construction of buildings for the effective use of energy and requirements for green building practices shall be administered in accordance with the 2012 International Energy Conservation Code as adopted, with amendments, by Chapter 10-7, "Energy Conservation Code," B.R.C. 1981, and Chapter 10-7.5, "Green Building and Green Points Program," B.R.C. 1981.

(cc)  Section M1301.1.1, "Flood-resistant installation," is repealed and reenacted to read:

M1301.1.1 Flood-resistant installation. In floodplains, as established in Title 9, Land Use Code, B.R.C. 1981, the mechanical appliances, equipment and systems shall be located or installed in accordance with the applicable provisions of Title 9, Land Use Code, B.R.C. 1981.

(dd)  A new Section M1308.3, "Rooftop equipment support and clearances," is added to read:

M1308.3 Rooftop equipment support and clearances.

(1) Mechanical equipment placed, replaced, or resting over roofing shall be supported by curbs or legs which shall be flashed to the roofing and made watertight. Mechanical equipment includes, but is not limited to, heating equipment, cooling and refrigeration equipment, ventilating fans, blowers, and other similar devices located on the roof.

(2) Flat roofs. On roofs having a pitch of less than 2 in 12, mechanical equipment shall be supported on a solid curb greater in size than the equipment which it serves. Curbs may be manufactured or built-in-place. If built-in-place, the curb shall be covered with metal of at least 26 gauge. The metal shall be weather-tight. The curb shall be a minimum of 9 inches above the finished roof.

(A) Ducts less than 4 feet in width shall have at least 12 inches clearance from the finished roof surface to the bottom of the duct.

(B) Ducts between 4 feet and 8 feet in width shall have at least 24 inches clearance from the finished roof surface to the bottom of the duct.

(C) Ducts over 8 feet in width shall have at least 36 inches clearance from the finished roof surface to the bottom of the duct.

(3) Pitched roofs. On roofs having a roof pitch exceeding 2 in 12, mechanical equipment may be set on legs which provide a minimum of 11 inches clearance between the finished roof surface and the equipment frame.

(ee)  Section M1401.5, "Flood hazard," is repealed and reenacted to read:

M1401.5 Flood hazard. In floodplains, as established in Title 9, Land Use Code, B.R.C. 1981, heating and cooling equipment and appliances shall be located or installed in accordance with the provisions of Title 9, Land Use Code, B.R.C. 1981.

(ff)  Section M1601.4.9, "Flood hazard areas," is repealed and reenacted to read:

M1601.4.9 Flood hazard areas. In floodplains, as established in Title 9, Land Use Code, B.R.C. 1981, duct systems shall be located or installed in accordance with the provisions of Title 9, Land Use Code, B.R.C. 1981.

(gg)  A new sentence is added to Section M1602.1, "Return air," to read:

Within individual dwelling units there shall be at least one return air opening on each floor.

(hh)  Section M2001.4, "Flood-resistant installation," is repealed and reenacted to read:

M2001.4 Flood-resistant installation. In floodplains, as established in Title 9, Land Use Code, B.R.C. 1981, boilers, water heaters and their control systems shall be located or installed in accordance with the provisions of Title 9, Land Use Code, B.R.C. 1981.

(ii)  Section M2201.6, "Flood-resistant installation," is repealed and reenacted to read:

M2201.6 Flood-resistant installation. In floodplains, as established in Title 9, Land Use Code, B.R.C. 1981, tanks shall be located or installed in accordance with the provisions of Title 9, Land Use Code, B.R.C. 1981.

(jj)  A new Section M2303, "Solar photovoltaic power systems," is added to read:

M2303 Solar photovoltaic power systems. Solar photovoltaic power systems shall also meet the provisions of section E3804, as amended.

(kk)  Section G2404.7, "Flood hazard," is repealed and reenacted to read:

G2404.7 Flood hazard. In floodplains, as established in Title 9, Land Use Code, B.R.C. 1981, the appliance, equipment, and system installations regulated by this code shall be located or installed in accordance with the provisions of Title 9, Land Use Code, B.R.C. 1981.

(ll)  Items 2 and 3 of Section G2427.8, "Venting system termination location," are amended by adding a new sentence to the end of each Items 2 and 3, reading:

Vents shall terminate a minimum of 18 inches (46 mm) above finished grade in the immediate vicinity of each vent.

(mm) Section P2503.7, "Water supply system testing," is repealed and reenacted to read:

P2503.7 Water supply system testing. Upon completion of the water supply system or a portion of it, the system or portion completed shall be tested and proved tight under a water pressure of not less than the working pressure of the system or by an air test of not less than 100 psi (689.5 kPa). This pressure shall be held for not less than 15 minutes. The water used for tests shall be obtained from a potable water source.

(nn)  The Exception to Section P2601.2, "Connections to drainage system," is deleted in its entirety.

(oo)  Section P2601.3, "Flood hazard areas," is repealed and reenacted to read:

P2601.3 Flood hazard areas. In floodplains, as established in Title 9, Land Use Code, B.R.C. 1981, plumbing fixtures, drains, and appliances shall be located or installed in accordance with the provisions of Title 9, Land Use Code, B.R.C. 1981.

(pp)  The first sentence of Section P2602.2, "Flood-resistant installation," is repealed and reenacted to read:

In floodplains, as established in Title 9, Land Use Code, B.R.C. 1981:

Items 1 and 2 remain unchanged.

(qq)  Section P3001.3, "Flood-resistant installation," is repealed and reenacted to read:

P3001.3 Flood-resistant installation. In floodplains, as established in Title 9, Land Use Code, B.R.C. 1981, drainage, wastes, and vent systems shall be located and installed to prevent infiltration of floodwaters into the systems and discharges from the systems into floodwaters.

(rr)  Section P3009, "Gray water recycling systems," is deleted in its entirety.

(ss)  Section P3101.5, "Flood resistance," is repealed and reenacted to read:

P3101.5 Flood resistance. In floodplains, as established in Title 9, Land Use Code, B.R.C. 1981, vents shall be located or installed in accordance with the provisions of Title 9, Land Use Code, B.R.C. 1981.

(tt)  A new Section E3804, "Solar photovoltaic power systems," is added to read:

E3804 Solar photovoltaic power systems. Solar photovoltaic power systems shall meet the provisions of sections 605.11 through 605.11.3.2.3 of the City of Boulder Fire Code.

(uu)  Section E4209.3, "Accessibility," is amended by adding the following to the end of the section:

Equipment shall be accessed by a panel with a minimum size of 12 inches (305 mm).

(vv)  Section AJ102.5, "Flood hazard areas," is repealed and reenacted to read:

AJ102.5 Flood hazard areas. Work performed in existing buildings located in a floodplain, as established by Title 9, Land Use Code, B.R.C. 1981, shall be done in accordance with the applicable provisions of Title 9, Land Use Code, B.R.C. 1981.

(ww) A new footnote notation "b" is added to the heading and a new footnote "b" is added to AP Table AP103.3(2), "Load values assigned to fixtures," reading:

b. For the purpose of determining the largest instantaneous demand required in order to size a water meter, or for determining the amount of the plant investment fee, this table is repealed and replaced by the Fixture Unit/GPM Demand Chart and PIF Computation sheet found at Appendix A to Chapter 11-1, "Water Utility," B.R.C. 1981.

Ordinance Nos. 5850 (1996); 7142 (2001); 7287 (2003); 7331 (2004); 7476 (2006); 7566 (2007); 7925 (2013)


1 Adopted by Ordinance No. 7304.

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