Boulder County Building Publications
Residential Plan Checklist B24

Based on the Boulder County Building Code, and the 2021 International Residential Code (IRC) including Appendix AE, AF, AH, AJ, AM, AO, AQ, AR, AS, AT, AU, AX, and RD.

The items listed below are minimum code requirements with which your project must be in compliance. Approval of the plans does not permit the violation of any part of the Boulder County Code. Contact the Building Safety & Inspection Services team at 720-564-2640 with questions.

Inspection Notes

The set of approved plans must be available to the building inspector on the site when inspections are made. Failure to have the county approved plans on the site at the time of inspection may result in no inspection performed or approved. A paid re-inspection fee will be required prior to scheduling a follow-up inspection.

Licensing Requirements

Since July 1, 2008, building contractors, HVAC contractors, and roofing contractors require licensing through Boulder County. Electricians and plumbers must be state-licensed.

Wildfire Requirements

1. See the Boulder County Land Use Department Publication titled Ignition- Resistant Construction for more information. (Boulder County Building Code Amendments (BCBCA) R390)

Wildfire Zone 1 (West County) and Wildfire Zone 2 (East County) require the following ignition resistant construction:

• • Class “A” roof coverings
  • Gutter/ downspout
  • Spark arrestors
  • Fences, retaining walls
  • Overhanging projections
  • Exterior walls
  • Deck, appendages, and projections
  • Exterior windows and glazing; Exception: Wildfire Zone 2
  • Exterior doors; Exception: Wildfire Zone 2
  • Vents

Wildfire Zone 1 (West County) and Wildfire Zone 2 (East County) – Wildfire defensible space inspection is required to be completed prior to the foundation inspection and a wildfire mitigation inspection is required to be completed at final inspection. Call 303-441-3930 with inquiries or to schedule an inspection.

Sprinkler Requirements

2. A sprinkler system meeting the requirements of NFPA 13D or IRC P2904 must be installed throughout the dwelling. Provide proof of sprinkler plan review and rough sprinkler inspection report from the fire district or other certified inspector prior to the rough framing inspection. Provide the final inspection report prior to the final inspection. See the Boulder County Land Use Department Publication titled Residential Fire-Protection System for more information. (2021 IRC or Boulder County Building Code Amendments (BCBCA) R313)

Foundation, Basement, and Underfloor Area Requirements

3. Burial Depth Requirements – See the Boulder County Land Use Department Publication titled Burial Depth, for more information.

Electrical – Direct burial conductors shall be a minimum of 24-inches deep, non-metallic conduit 18-inches deep or 24-inches under driveways. (IRC Table E3803.1)

Water Lines – Shall be a minimum of 36-inches deep. (IRC P2603.5)

Gas Service Piping – Installed a minimum of 12-inches below grade or 8-inches below grade where serving individual outside appliances. An 18 AWG yellow insulated tracer wire must be installed adjacent to underground nonmetallic gas piping and terminate above grade at each end. (IRC G2415.12 and G2415.17.3)

4. Underground plumbing pipe shall have a solid and continuous load-bearing support. Piping cannot bear on rocks. Pipes passing under a footing or through foundation wall shall be provided with a relieving arch or a sleeve. Trenches parallel to footing shall not extend below the 45° plane of the edge of the footing.Water piping must be buried a minimum 36-inches deep. Water service pipe may be installed in the same trench as the building sewer provided the sewer pipe material is listed for underground use within the building, or the water service pipe is separated from the sewer by a minimum distance of 5-feet horizontally or elevated at least 12-inches above and to one side of the sewer line. See the Boulder County Land Use Department Publication titled Burial Depth for more information. (IRC P2603.5, P2604.2, P2604.4, P2605.1)
5. Frost depth to the bottom of the foundation footings must be as noted on the engineered plans. If not noted, the frost depth to the bottom of the footings must be a minimum of 30-inches below finished grade. (IRC Table R301.2) and Boulder County Building Code Amendments (BCBCA) Table R301.2(1))
6. Caisson and helical pier foundations will not be inspected by Boulder County. A qualified, Colorado-licensed engineer must perform the placement, drilling, and reinforcement of drilled piers. A signed, sealed and dated inspection report must be provided to Building Safety & Inspection Services prior to the rough inspections. (BCBCA 110.3)
7. A perimeter drain system that discharges to an approved drainage system is required around all foundations that enclose usable spaces below grade. Foundations that retain earth and enclose interior spaces below grade must be damp proofed. (IRC R405.1, R406.1)
8. Under floor protection is required for crawlspaces with a clearance greater than 36” and shall be provided with 1/2” gypsum, 5/8” wood structural panel membrane, or equivalent on the underside of the floor framing member. Boulder County considers this as a space that may be used for storage. (BCBCA R302.13)
9. Garage and carport floor surfaces must be approved noncombustible materials. Floors must be sloped to facilitate the movement of liquids to a drain or toward the main vehicle entry doorway. (IRC R309.2)
10. Foundation plates and sills must be bolted to the foundation wall as prescribed on the engineered plans. If not noted, bolts shall have a minimum diameter of 1/2-inch, embedded at least 7-inches and spaced not more than 6-feet apart. A minimum of 2 bolts are required per plate section, with one bolt located within 12-inches of each end of each plate. (IRC R403.1.6)

Manufactured or Factory-Built Buildings

11. Manufactured Home & Factory Built Housing Requirements.

Installation Manual: Installation of a manufactured home shall be in accordance with the manufacturer’s installation instructions. Where the installation instructions are unavailable, installation shall be in accordance with the following standards:

A. Temporary Foundation Installations: 8 CCR 1302-14, Sections 1.32 and 2.14.2.

B. Permanent Foundation Installations: Permanent Foundation, Guide for Manufactured Housing, September 1996 (amended).

C. Engineered Foundation System as required by Boulder County Building Department.

D. IRC Appendix AE.

A copy of the manufacturer’s instructions or the standards shall be available on site at the time of installation and inspection.

HUD Manufactured Units

Label: Each section of each home shall be labeled by the inspection agency. The permanently affixed label is located on the rear of each unit.

Data Plate: Each HUD home shall bear a data plate located near the main electrical panel, master bedroom closet, laundry room, or other readily accessible and visible location.

Factory-Built Units

Colorado State Label: The State of Colorado, Division of Housing insignia will be found in the kitchen sink cabinet.

Installation Insignia: An insignia placed within 30” of the electric meter housing, or service entry, or on the meter housing.

For more information:

• • • • Webpage: Boulder County Manufactured Home and Factory Built Housing
      • Webpage: Colorado Division of Housing, Modular Buildings

Rough Framing and Wood Requirements

12. The complete rough inspection is to be made after the rough framing, rough electric, rough plumbing, and rough heat and ventilation are complete. The building should be fully enclosed with the roof covering and siding in place. (BCBCA 110).
13. Lumber, plywood, fiberboard, structural logs, and glued laminated timber must be identified by a grade mark or certificate of inspection issued by an approved agency. (IRC R502.1, R602.1, and R802.1).
14. Wood in contact with the ground that supports structures for human occupancy must be approved pressure- preservative-treated wood. (IRC R317.1.2).
15. Protection from decay shall be provided in the following locations by the use of naturally durable wood or wood that is preservative treated in accordance with AWPA U1. (IRC R317):

A. Wood joists closer than 18-inches and wood girders closer than 12-inches to grade located within foundation periphery.

B. Wood framing members that rest on concrete or masonry foundation walls and are less than 8-inches from the exposed ground.

C. Sills and sleepers on a concrete or masonry slab that is in direct contact with the ground.

D. Wood girders entering concrete or masonry walls with a clearance less than1/2-inch.

E. Wood siding, sheathing, and wall framing less than 6-inches above the ground.

F. Wood members supporting moisture-permeable floors or roofs that are exposed to the weather.

G. Wood furring strips or wood members attached directly to the interior of below grade exterior masonry or concrete walls.

H. Wood in contact with the ground, embedded in concrete in direct contact with the ground or embedded in concrete exposed to the weather that supports permanent structures intended for human occupancy shall be approved pressure-preservative-treated wood.

16. Accessible under-floor areas shall be provided with a minimum 18-inches x 24-inches opening through the floor or 16-inches x 24-inches opening through the perimeter wall. When the access is through a below-grade wall an areaway of not less than 16-inches x 24-inches must be provided. Where equipment is located beneath the floor, the access opening must be within 20-feet of the equipment and allow the removal of the largest piece of equipment. (IRC R408.4 and M1305.1.3)
17. Basements greater than 200 square feet and every sleeping room shall have at least one operable emergency and rescue opening or a door to the exterior. Emergency escape and rescue openings shall meet the following requirements: A minimum clear width of 20-inches, a minimum clear height of 24-inches, with a total net clear opening of 5 square feet for grade level windows and 5.7 square feet for all others. A sill height of not more than 44 inches measured from the finished floor to the bottom of the clear opening. Window wells for emergency escape and rescue shall provide a minimum net area of 9 square feet with minimum horizontal projection and width of 36-inches. The area of the widow well shall allow the emergency escape and rescue opening to fully open. See the Boulder County Land Use Department Publication titled Emergency Escape and Rescue Openings, for more information. (IRC R310)
18. Columns must be restrained to prevent lateral displacement at the bottom end to insure against uplift. (IRC R301.2.1, R407.3)
19. Fire blocking shall be installed to cut off all concealed draft openings in the following locations: (IRC 302.11):

A. In concealed spaces of stud walls and partitions, including furred spaces, vertically at the ceiling and floor levels, and at 10-feet horizontal intervals.

B. At interconnections between concealed vertical and horizontal spaces such as occur at soffits, drop ceilings, and cove ceilings.

C. In openings around vents, pipes, ducts, cable, wires, chimneys, fireplaces, and similar openings that afford a passage for fire at ceiling and floor levels.

D. In concealed spaces between stair stringers at the top and bottom of the run, and between studs in line with the run of the stairs at unfinished walls.

20. Stairways must be at least 36-inches in width. Handrails shall not project more than 4½-inches. The maximum rise may not exceed 7¾-inches. The minimum tread depth may not be less than 10-inches. Minimum headroom is 6-feet, 8-inches. For stairways with solid risers a nosing of ¾-inch to 1¼-inches shall be provided. When open risers are used the opening between the treads shall not allow the passage of a 4-inch sphere. Landings must be provided at the top and bottom of the stairway that is the width of the stairway measuring at least 36-inches in the direction of travel. See the Boulder County Land Use Department Publication titled Residential Stairways, Handrails, Ramps, and Guards for more information. (IBC 1011, IRC R311.7)
21. Winding stairways require a 10-inch tread depth at a point 12-inches from where the tread is the narrowest. Winder treads shall have a minimum tread depth of 6-inches. See the Boulder County Land Use Department Publication titled Residential Stairways, Handrails, Ramps, and Guards, for more information. (IRC R311.7.5.2.1)
22. Structural insulated panels (SIPs) must be installed per the listing. Provide a panel layout schedule at the rough inspection. A Colorado-licensed engineer must inspect panels supporting other than uniform loads and the written report provided to the Building Inspection Services. (IRC R610, BCBCA 110.3.10 and 110.4)
23. Insulated concrete form (ICF) wall systems must be designed by a Colorado-licensed engineer or be designed per IRC R611 to include reinforcement, lintels, sill and ledger anchorage. Foam insulation may not be exposed to the interior of the building. (IRC R608)
24. One layer of No. 15 asphalt felt, free from holes and breaks, complying with ASTM D 226 for Type 1 felt or other approved water-resistive barrier shall be applied over studs or sheathing of all walls within the exterior wall envelope. (IRC R703.2)
25. Ceiling heights for habitable rooms, hallways, bathrooms, toilet rooms, laundry rooms, and basements shall be a minimum of 7-feet measured from the finished floor to the lowest projection of the ceiling. Non-habitable basements may have a ceiling height of 6-feet, 8-inches with clearance below beams and ducts of 6-feet, 4-inches. Bathroom may have a ceiling height of 6-feet, 8-inches at the fixture front clearance area and over the fixture. (IRC R305.1)
26. Attic access must be provided for attics that exceed 30 square feet and that have a vertical height of 30-inches or greater. The access must be located in a hall or readily accessible location with a minimum 22-inches x 30-inches access opening. The access must provide a minimum of 30-inches headroom. (IRC R807)
27. Roof ventilation (IRC R806):

A. Enclosed attic and rafter spaces must have cross ventilation for each space through screened openings. The total net free ventilating area shall not be less than 1 to 150 of the area of the space ventilated. The area may be reduced to 1 to 300 if 50-80% is provided by ventilators located in the upper portion of the space or if a vapor barrier not exceeding 1 perm is installed on the warm side of the ceiling. At least a 1-inch space is required between the roof sheathing and the insulation at the location of the vent. (IRC R806.1)

B. Unvented attic and unvented enclosed rafter assemblies. Unvented attics and unvented enclosed roof framing assemblies created by ceilings that are applied directly to the underside of the roof framing members and structural roof sheathing applied directly to the top of the roof framing members/rafters, shall be permitted where all the conditions of R316 and R806.5 are met.

28. Rafters must be framed to a minimum 1-inch nominal ridge board that is not less than the depth of the cut end of the rafter or to each other using a gusset plate. Hip, and valley rafters shall be a minimum of 2-inches and not less in depth than the cut end of the rafter. Hip and valley rafter shall be supported at the ridge by a brace to a bearing partition or be designed. (IRC R802.3)
29. Rafters and ceiling joists having a depth-to-thickness ratio exceeding 5:1 shall be provided with lateral support at points of bearing to prevent rotation. Rafters and ceiling joists having a depth-to-thickness ration exceeding 6:1 shall be supported laterally by solid blocking, diagonal bridging or a continuous 1-inch by 3-inch wood strip nailed across the rafters. (IRC R802.8)
    Roof trusses or rafters must be attached to supporting walls with approved hurricane clips. Trusses must be braced to prevent rotation and to provide lateral stability in accordance with the construction documents and the individual truss design drawings. (IRC R502.11.2, R802.11)
30. Trusses must be designed and fabricated in accordance with ANSI/TPI 1. A licensed professional shall prepare the truss design. Trusses must be legibly marked within 2-feet of the center to identify the manufacturer, the design load, and the spacing. Truss engineering and layout must be provided at the site at the rough framing inspection. (IRC R502.11 and R802.10)
31. Roofing covering:

A. Roofing material installed in the mountain areas is limited to Class ”A” roof coverings. Shingle installation shall meet the manufacturer’s high-wind installation procedures in areas where wind load is greater than 110 mph (V3S). See the Boulder County Wind Speed map for wind speed information. (IRC Chapter 9, BCBCA R301.2.1, R390, and manufacturer’s listing)

B. Asphalt shingles shall be Class 4 impact resistant, tested in accordance with UL 2218, and installed in accordance with the manufacturer’s installation instructions. (BCBCA IRC R905.2.4.2 and BCBCA IBC 1504.8.1)

32. Roofs decks and enclosed roofed areas must be provided with roof drains installed at the low point of each roof. Where roof drains are installed, overflow drains or scuppers are required. (IRC R903.4).
33. Exterior finish materials must conform to the conditions of your Site Plan Review to include: roof covering, siding, ignition resistant construction, color requirements, conforming light fixtures which comply with the approved lighting plan, and re-vegetation requirements.

Glazing And Window Requirements

34. All habitable rooms shall be provided with aggregate glazing area for natural light of not less than 8% of the floor area of such rooms. The glazed areas need not be installed in rooms where section M1505 is satisfied, and artificial light is provided at an average of 6 footcandles at a height of 30 inches. Sleeping rooms must meet egress requirements. (IRC R303.1)
35. Safety glazing shall be installed in the following hazardous locations and be permanently labeled as safety or tempered glazing: glazing panels in doors; glazing enclosing spas, bathtubs or showers; glazing panels adjacent and within 24-inches of the edge of a door; glazing panels greater than 9 square feet within 18-inches of the floor; glazing used for railings; glazing used for barriers for swimming pools and spas; and glazing enclosing stairways, landings, and ramps within 36-inches horizontally of a walking surface. See the Boulder County Land Use Department Publication titled Safety Glazing, for more information. (IRC R308).
36. Skylights must be: (IRC R308.6 and Boulder County Building Code Amendments (BCBCA) Table N1102.1):

A. Laminated glass (with restrictions).

B. Fully tempered glass (with retaining screen).

C. Heat-strengthened glass (with retaining screen).

D. Wired glass (with retaining screen in multiple glazing condition only).

E. Approved rigid plastic.

F. Skylight U-factor required U-0.35.

G. Skylights installed on roofs flatter than 3 units vertical to 12 units horizontal must be mounted on a curb 4-inches above the roof.

Heating and Ventilation Requirements

37. Crawl spaces shall be provided with conditioned air in compliance with IRC 408.3 Crawl space walls shall be insulated in accordance with BC Amendments Table N1102.1.2. Crawl space wall insulation shall be secured to the wall and extend downward from the sill plate to not less than the top of the foundation wall footing. Exposed earth in crawl space foundations shall be covered with a continuous Class I vapor retarder in accordance with the International Building Code® or International Residential Code, as applicable. Joints of the vapor retarder shall overlap by 6-inches (153 mm) and be sealed or taped. The edges of the vapor retarder shall extend not less than 6-inches (153 mm) up stem walls and shall be attached and sealed to the stem walls. (Boulder County Building Code Amendments (BCBCA) N1102.2.10).

Ventilated crawlspaces. Ventilated crawlspaces shall be provided with insulation in accordance with BCBCA Table N1102.1.2, IRC R408.1 and R408.2.

38. Ventilation (IRC R303.1, BCBCA N1103.6 and BCBCA Table N1103.6.2):

A. Habitable rooms must be provided with outdoor openings for ventilation equal to at least 4% of the floor area and shall have heating facilities capable of maintaining 68° at 3-feet above the floor and 2-feet from exterior walls.

B. The windows need not be openable in a room where an opening is not required to be an egress window, and a whole house mechanical ventilation system designed to meet IRC M1505.4 is installed.

39. Bathroom exhaust fans shall exhaust directly to the exterior and must be provided in bathrooms where windows of at least 3 square feet are not provided. The mechanical ventilation must be capable of providing an exhaust capacity of 50 cfm intermittent or 20 cfm continuous exhaust. (IRC R303.3 and Table M1505.4.4)
40. Dryer vents must be rigid metallic, independent of all other systems, shall terminate outside the building, be equipped with a back draft damper, and sized and terminated per the manufacturer. The maximum length of the exhaust duct shall be 35-feet (Unless approved under the manufacturer’s listing) from the connection to the transition duct from the dryer to the outlet terminal. Where fittings are used, the maximum length of the exhaust duct shall be reduced in accordance with (IRC Table M1502.4.6.1) Flexible transition ducts are limited to 8-feet, shall not be concealed within construction, and shall be listed and listed per UL 2158A. (IRC M1502)
41. Appliances and equipment shall be installed in accordance with the conditions of their listing. Manufacturer’s installation instructions must be available at the time of the inspection. (IRC G2408.1, M1307.1, M1401.1, M1902.2)
42. Appliances shall be accessible for inspection, service, repair and replacement without removing permanent construction. 30-inches of working depth and width shall be provided in front of the control side of an appliance. (IRC M1305.1)
43. Gas and solid fuel appliances located in a garage and hazardous locations shall be elevated so the source of ignition is at least 18-inches above the floor. Rooms and spaces that are communicate directly with the garage and are not part of the living space shall be considered as part of the garage. Appliances located in garages must be installed at least 6-feet above the floor or protected from motor vehicle impact. (IRC G2408.2, G2408.3)
44. Combustion air is required for all liquid fuel, solid fuel and gas appliances. (IRC M1701.1, G2407)
45. Gas burning appliances may not be located in or obtain combustion air from: a sleeping room, bathroom, toilet room, or storage closet unless it is a direct vent appliance or installed in an enclosure that opens only into a bedroom or bathroom in and such enclosure is provided with a solid weather-stripped door, a self-closing device and all combustion air is taken from the outdoors. (IRC G2406.2)
46. Gas logs installed in solid fuel burning fireplaces shall be tested in accordance with ANSI Z21.60 and installed per the manufacturer’s installation instructions. Gas logs installed in bedrooms must be direct vent or provided with an approved source of outside combustion air. The approved gas log set must be installed in the Solid fuel burning appliances at the final inspection. (IRC G2406, G2432, and G2434) Solid-fuel-burning fireplace stoves, fireplace inserts, or wood stove appliances shall conform with emissions testing, certification and labeling requirements per Title 30, Article 28, Sections 402-405 of the Colorado.
47. Revised Statutes. The Air Pollution Control Division of the Colorado Department of Health must certify these appliances to meet the emissions standards of Section IV of Regulation No. 4 of Volume I of the Colorado Air Quality Control Commission as EPA Phase II or Colorado Phase III solid-fuel-burning devices. Solid-fuel burning devices shall meet the most current emissions standards for wood stoves established by the Colorado Air Quality Control Commission, or any other clean-burning device that is approved by the commission. (BCBCA IMC Chapter 9)
48. B, BW, and L vents and factory-built chimneys must be provided with a clearance to combustibles per the manufacturer’s listing. Where vents pass through insulated assemblies, they must be provided with an insulation shield. A clearance of 9-inches is required between single wall vent connectors and combustibles. Gas vents must penetrate through the roof flashing, jack or thimble and terminate in a listed cap or per the manufacturers listing. Decorative shrouds installed at terminations shall be listed and installed per the manufacturer. (IRC G2425, G2426, G2427)
49. Chimneys shall be protected with a spark arrester consisting of 19 gage galvanized steel or 24 gage stainless steel, with openings not exceeding ½-inch. (IRC R1003.9.2)

Electrical Requirements

50. All electrodes present at each structure shall be bonded together to form one grounding electrode system to include: Concrete Encased Electrodes (UFER), water piping, ground rings, grounding rods, and plate electrodes. Bonding shall ensure electrical continuity. The electrode conductor must be connected in an approved manner and inspected prior to concealing. (NEC 250.24, 250.28, 250.32, 250.50)
51. All electrical receptacle, switch, light, and junction boxes shall be made up using proper mechanical connectors at time of rough inspections. This includes non-grounded, grounded, and grounding conductors.
52. Tamper -resistant Receptacle outlets are required in every kitchen, family room, dining room, living room, parlor, library, den, sunroom, bedroom, recreation room or similar dwelling areas, including attached and detached garages and accessory buildings to dwelling units, spaced so that no point measured horizontally along the wall line exceeds 6-feet from a receptacle outlet. (NEC 210.52, 406.3, 406.12)

A. Counters 12-inches in width or wider shall have receptacles placed no more than 20-inches above the countertop and spaced so no point exceeds 24-inches from a receptacle outlet.

B. Island and peninsula counters with a length at least 24-inches and a width of 12-inches or greater must be equipped with at least one outlet.

C. At least one receptacle outlet shall be installed in a bathroom within 36-inches of each basin.D. At least one receptacle shall be installed for laundry equipment, in unfinished basements, and in each car space of attached and detached garages. The branch circuit supplying the garage receptacles shall not supply outlets outside of the garage. (NEC 210.52(G)(1))

E. Not less than one receptacle that is readily accessible from grade level and located not more than 6 feet 6 inches above grade, shall be installed outdoors at the front and back of each dwelling unit having direct access to grade level. Balconies, decks, and porches that are accessible from inside of the dwelling unit shall have at least one receptacle installed within the perimeter of the balcony, deck, or porch.

F. Attics or crawlspaces containing equipment must be provided with at least one receptacle within 25-feet of the equipment.

G. Hallways of 10 feet or more in length shall have at least one receptacle outlet. The hall length shall be considered the length measured along the centerline of the hall without passing through a doorway. Foyers that are not part of a hallway and is greater than 60 square feet shall have a receptacle(s) located in each wall space that is 3 feet or more in width. Doorways, door-side windows that extend to the floor, and similar openings shall not be considered as wall space.

53. A minimum of two 20-amp rated branch circuits shall serve receptacles in the kitchen, pantry, breakfast area, and dining area. At least one 20-amp branch circuit shall supply bathroom receptacles and at least one 20-amp branch circuit shall supply laundry. Refrigerator receptacle can be connected to one of the two required kitchen branch circuits or from an individual branch circuit rated 15 amperes or greater. (NEC 210.52(B))
54. Ground fault protection shall be provided on all 125-volt through 250-volt single phase 15 and 20-ampere receptacle outlets installed in kitchens including butler’s pantries, bathrooms, garages and accessory buildings, outdoors, crawl spaces, basements, within 6’ of all other sinks, and laundry areas. Ground-fault circuit interrupters shall be installed in readily accessible locations. (NEC 210.8, 210.8(D))
55. A. Combination type arc-fault circuit interrupters must be installed on all 120-volt 15 and 20-amp branch circuits installed in kitchens including butler’s pantries, dishwashers and disposal, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sun rooms, recreation rooms, closets, hallways, laundry areas and similar rooms or areas. Arc-fault circuit interrupters shall be installed in readily accessible locations. (NEC 210.12)
    B. Whenever a branch circuit wiring is modified, replaced, or extended in any of the areas specified in 55A above, the branch circuit shall be protected by one of the following: (NEC 210.12(B))
    1. A combination-type AFCI circuit breaker located at the origin of the branch circuit
    2. A receptacle AFCI located at the first receptacle outlet of the existing branch circuit.
56. At least one wall switch-controlled lighting outlet shall be installed in every habitable room, bathroom, kitchen, hallway, stairways, attached garage, detached garage and assessor building with electric power, and at the exterior side of each outdoor exit door having grade level access. Attics, under floor spaces, utility rooms and basements containing equipment or used for storage must be provided with a switch operated light. (NEC 210.70)
57. Smoke alarms shall comply with UL 217 and UL 2034. Smoke alarms are to be powered by the building’s wiring with battery backup and shall be interconnected so the actuation of one alarm will activate all alarms in the dwelling unit. Interconnection of smoke alarms shall not be required where alterations or repairs do not result in removal of interior wall or ceiling finishes exposing the structure, unless there is an attic, crawl space or basement available that could provide access for interconnection without the removal of interior finishes. Smoke alarms shall be permitted to be battery operated where installed in buildings without commercial power. Smoke alarms shall be installed in the following locations (IRC R314):

A. In each sleeping room.

B. Outside each sleeping area in the immediate vicinity of the bedrooms.

C. One on each additional story including basements and habitable attics.

D. Smoke alarms shall be installed not less than 3 feet horizontally from the door or opening of the bathroom that contains a bathtub or shower unless this would prevent placement of a smoke alarm in locations listed above.

E. In the hallway and in the room open to the hallway in dwelling units where the ceiling height of a room open to a hallway serving bedrooms exceeds that of the hallway by 24 inches or more.

A Carbon Monoxide alarms shall comply with UL 2034 and UL 217. Carbon Monoxide alarms are required in a single-family dwelling that has fuel-fired appliance(s), or an attached garage. The alarm must be installed within 15-feet of the entrance to each sleeping room (State of Colorado requirement) and must be listed by a nationally recognized, independent lab. Where a fuel-burning appliance is located within a bedroom or its attached bathroom, a carbon monoxide alarm shall be installed within the bedroom. Plugs into a dwelling’s electrical outlet and has a battery backup. They may be combined with a smoke-detecting device if the combined device complies with applicable law. (IRC R315)

58. Clothes closet lighting shall be limited surface-mounted or recessed incandescent fixtures with completely enclosed lamps, surface-mounted or recessed fluorescent fixtures, surface-mounted fluorescent or LED luminaires identified as suitable for installation within the closet storage space.

Surface mounted and recessed fixtures shall be installed on the wall above the door or on the ceiling with the following clearances between the fixture and the nearest point of a storage space as follows (NEC 410.16):

A. Incandescent fixtures or LED shall have a minimum 12-inch clearance.

B. Fluorescent fixtures shall have minimum 6-inch clearance.

C. Recessed incandescent or LED luminaires with completely enclosed light source shall have a minimum of 6” clearance.

E. Recessed fluorescent fixtures shall have a minimum 6-inch clearance.

59. Working space must be provided around energized equipment for servicing and maintenance. The minimum dimensions shall not be less than 36-inches in depth and 30-inches in width in front of the equipment. Working space shall extend to at least 6-feet, 6-inches above the floor. (NEC 110.26)
60. Electrical fixtures installed in wet or damp locations shall be installed so that water cannot enter or accumulate in wiring compartments or other electrical parts. Fixtures installed in wet locations must be labeled “suitable for wet locations”. Fixtures installed in damp locations must be labeled “suitable for damp locations” or “suitable for wet locations”. Switches or circuit breakers located in wet locations or outdoors must be enclosed in a weatherproof enclosure. Outdoor receptacles must have a weatherproof enclosure and an in-use cover. (NEC 410.10(A), 404.4, 406.9(A))

Cord-connected fixtures, hanging fixtures, track lighting, pendants, and ceiling fans shall not be located within 3-feet horizontally and 8-feet vertically from the top of a tub or shower rim. (NEC 410.10(D))

61. Swimming pools, fountains, hot tubs, spas, and hydro-massage “Jacuzzi” tubs and similar installations shall comply with all provisions of the IRC for the approval of bonding equipment and lighting. All 15 and 20 amp, single-phase 125-volt receptacles located within 20-feet of the inside walls of pools, outdoor spas and hot tubs shall be protected by a GFCI circuit. Motors and equipment must be accessible without damaging the building structure or building finish. (NEC 680)
62. The reinforcing shell of the pool shell, metal forming shells, coping stones, deck, brackets of niche fixtures, metal fittings, and electrical equipment, located less than 5-feet horizontally and less than 12-feet above maximum water level of swimming pools and built in place hot tubs shall be bonded together. The parts specified above shall be connected to an equipotential bonding grid. (NEC 680.26)

Plumbing Requirements

63. Piping must be inspected and tested prior to concealing. It shall be protected against physical damage, corrosion and freezing. Must be approved for use and bear the identification of the manufacturer. (IRC P2503, P2603, P2609)
64. Where drainage is roughed-in for future fixtures, the drainage unit values of the future fixtures shall be considered in determining the required drain size. Such future installation shall be terminated with an accessible permanent plug or cap fitting. (IRC P3005.1.5)
65. A water closet (toilet), lavatory or bidet shall not be closer than 15-inches from its center to any side wall, partition or vanity or closer than 30 inches center-to-center between adjacent fixtures. There shall be a clearance of not less than 21-inches in front of a water closet, lavatory or bidet to any wall, fixture or door. (IRC P2705)
66. Showers and tub/shower combination valves shall be balanced-pressure, thermostatic or combination balanced-pressure balance/thermostatic valves that conform to the requirements of ASSE 1016/ASME 112.1016/CSA B125.16 or ASME A112.18.1/CSA B125.1. Such valves shall be equipped with a means to limit the maximum setting of the valve to 120°F. Bathtubs shall also have a water-temperature-limiting device to limit the maximum setting of the device to 120°F that conforms to ASSE 1070/ASME A112.1070/CSA B125.70. (IRC P2708.4, P2713.3)
67. Backflow prevention must be provided to prevent contamination from nonpotable liquids, solids or gases being introduced into the potable water supply in accordance with sections P2902.3.1 through P2902.3.7 and shall conform to Table P2902.3. This includes but is not limited to: hose connections, irrigation systems, boilers, solar systems, fire sprinklers, and dishwashers. (IRC P2902, Table P2902.3, P2717)

Insulation

68. Insulation and energy conservation shall meet Boulder County BuildSmart energy program (Boulder County’s green building program). See Boulder County Building Code Amendments (BCBCA) to Chapter 11 in the IRC. Insulation R-values and fenestration U-factors must conform to a HERS report (Performance energy path) or the Prescriptive energy path option per Table N1102.1.2. New conditioned structures shall comply with the Performance energy path and the Prescriptive energy path is limited to additions, alterations, remodels, and repairs as outlined in section N1109 Existing Buildings.
69. Foam plastic insulation 4 inches thick or less shall have a flame spread index of not more than 75 and a smoke development index of not more than 450 where tested in the maximum thickness and density intended for use in accordance with ASTM E84 or UL 723. Foam plastic insulation more than 4 inches in thickness shall have a flame spread index of not more than 75 and a smoke development index of not more than 450 where tested at a thickness of 4 inches in accordance with ASTM E84 or UL 723, provided that the end use is approved in accordance with section R316.6 using the thickness and density intended for use. Foam insulation must be separated from the interior of the building with a thermal barrier of not less than ½-inch gypsum board, 23/32 inch wood structural panel or a material that has been tested in accordance with NFPA 275, and shall meet the acceptance criteria of both the Temperature Transmission Fire Test and the Integrity Fire Test. A thermal barrier can be omitted in an attic or crawlspace if in compliance with sections R316.5.3 (attics) or R316.5.4 (crawl spaces). (IRC R316)
70. Combustible insulation shall be separated not less than 3 inches from recessed lights, fan motors and other heat-producing devices. (R302.14) Where vents pass through insulated assemblies, an insulation shield constructed of steel with a min. Thickness of 0.0187 inches (No. 26 gage) shall be installed to provide clearance between the vent and the insulation material. The clearance shall be per manufacturer’s installation instructions. Where vents pass through attic spaces, the shield shall terminate at least 2-inches above the insulation materials and shall be secured. (G2426.4) Recessed lights must be airtight if located in the building envelope to prevent air leakage between conditioned and unconditioned spaces and shall be IC-rated and labeled as having an air leakage rate not more than 2.0 cfm when tested in accordance with ASTM E 283 at a 1.57 psf (75 Pa) pressure differential. All recessed lights shall be sealed with a gasket or caulk between the housing and the interior wall or ceiling cover. (BCBCA N1102.4.5)
71. A vapor retarder shall be provided on the interior side of framed walls, floors and roof/ceilings of the building’s thermal envelope but not on below grade walls or where accumulation, condensation or freezing of moisture will not damage the materials. Wall assemblies in the building thermal envelope shall comply with the Class II or Class III vapor retarder requirements of Section R702.7 as outlined in Tables R702.7(2) or R702.7(2) of the 2021 IRC. A minimum vented air space shall be defined as one that is 3/8 of an inch or bigger. (BCBCA N1102.1.1, IRC R702.7) Comply with the manufacturer’s specification listing for the product installation.

Wallboard Requirements

72. The garage shall be separated from the residence and its attic by materials of not less than ½-inch gypsum board applied to the garage side. Garages shall be separated from all habitable rooms above the garage by not less than 5/8-inch Type X gypsum board or equivalent. Where the separation is a floor-ceiling assembly, the structure supporting the separation shall also be protected by not less than ½-inch gypsum board. (IRC Table R302.6)

Openings from a private garage directly into a room used for sleeping purposes shall not be permitted. (IRC 302.5.1)

Other openings between the garage and residence shall be equipped with solid wood doors not less than 1 3/8-inch in thickness, solid or honeycomb core steel doors not less than 1 3/8-inch thick, or 20-minute fire-rated doors. Doors shall be self-latching and equipped with a self-closing or automatic-closing device. (R302.5.1)

1. Enclosed space under stairs that is accessed by a door or access panel shall have walls, under-stair surface and any soffits protected on the enclosed side with ½-inch gypsum board. (IRC R302.7)
2. Water-resistant gypsum backing board used as the base or backer for adhesive application of ceramic tile or other required nonabsorbent finish material shall conform to ASTM C1178, C1278 or C1396. Use of water-resistant gypsum backing board shall be permitted on ceilings. Water-resistant gypsum board shall not be installed over a Class I or II vapor retarder in a shower or tub compartment and may not be used where there will be direct exposure to water, or in areas of continuous high humidity. All cut and exposed edges shall be sealed. (IRC R702.3.7)
3. Ceramic tile backer board materials used for wall tile in tub and shower areas and wall panels in shower areas shall be of materials listed in Table R702.4.2 and be installed in accordance with the manufacturer’s recommendations. Glass mat gypsum backer per ASTM C 1178, Fiber reinforced gypsum per ASTM C 1288, Non-asbestos fiber-cement backer per ASTM C1288 or ISO 8336, Category C, non-asbestos fiber mat-reinforced cementitious backer units per ASTM C1325. (IRC R702.4.2 Table R702.4.2)
4. Gypsum Board Applications:

Gypsum Board and Gypsum Panel products minimum thickness and Applications shall comply with IRC Table R702.3.5.

Supports and fasteners used to attach gypsum board and gypsum panel products shall comply with Table R702.3.5. Gypsum sheathing shall be attached to exterior walls in accordance with Table R602.3(1). Gypsum board and gypsum panel products shall be applied at right angles or parallel to framing members. All edges and ends of gypsum board and gypsum panel products shall occur on the framing members, except those edges and ends that are perpendicular to the framing members. Interior gypsum board shall not be installed where it is directly exposed to the weather or to water.

Gypsum boards or panels applied to ceilings shall be installed perpendicular to framing members, except when installing ½ inch or 5/8 inch thick boards or panels on framing members that are 16 inches o.c., shall be permitted to be installed parallel or perpendicular. Wall Gypsum boards or panels shall be permitted to be applied parallel or perpendicular to framing members.

Nail and screw types, sizes and spacing shall comply with Table R702.3.5.

Final Inspection Requirements

77. Buildings shall have approved address numbers, building numbers or approved building identification placed in a position that is plainly legible and visible from the street or road fronting the property. Numbers shall not be spelled out and shall not be less than 4 inches in height and not less than 0.5 inches in width. (IRC 319)
78. A means of egress shall be provided with a continuous and unobstructed path of vertical and horizontal egress travel from all portions of the dwelling to the required egress door without requiring travel through a garage. The required egress door shall open directly into a public way or to a yard or court that opens to a public way. 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. Other doors shall not be required to comply with these minimum dimensions. Egress doors shall be readily openable from inside the dwelling without the use of a key or special knowledge or effort. (IRC R311.1, R311.2)
79. There shall be a floor or landing on each side of each exterior door. The width of each landing shall be not less that the door served and shall have a dimension of not less than 36 inches measured in the direction of travel. The slope at exterior landings shall not exceed 2%. Landings or finished floors at the required egress door shall be not more than 1 ½ inches lower that the top of the threshold. The landing or floor on the exterior side shall be not more than 7 ¾ inches below the top of the threshold provided that the door does not wing over the landing or floor. Doors other than the required egress door shall be provided with landings or floors not more than 7 ¾ inches below the top of the threshold. A top landing is not required where a stairway with 2 or fewer risers is located on the exterior side of the door, provided that the door does not swing over the stairway. (IRC R311.3)
80. Handrails shall be provided on not less than one side of each flight of stairs with 4 or more risers and ramps with a slope exceeding 1:12. Handrails shall be mounted 34-inches to 38-inches above the nosing of the treads or finish surface of ramp slope. Handrails must be continuous for the entire length of the stairs and the ends shall be returned toward a wall, guard walking surface continuous to itself, or terminate to a post. Handrails adjacent to a wall shall have a space of not less than 1½-inch between the wall and the handrail. See the Boulder County Land Use Department Publication titled Residential Stairways, Handrails, Ramps, and Guards for requirements and more information. (IRC R311.7.8)

Handrail Grip Size Shall Be:

Type I – Circular Handrails shall have an outside diameter 1¼ inches to 2 inches. Non-circular handrails shall have a perimeter 4 to 6 ¼ inches and a cross section not more than 2 ¼ inches.

Type II – Handrails with a perimeter greater than 6¼ inches shall have a graspable finger recess area on both sides. The finger recess shall begin within ¾ inch measured vertically from the tallest portion of the profile and have a depth of not less than 5/16 inch within 7/8 inch below the widest portion of the profile. This required depth shall continue for not less than 3/8 inch to a level that is not less than 1 3/4 inches below the tallest portion of the profile. The width of the handrail above the recess shall be not less than 1 1/4 inches and not more than 2 ¾ inches.

81. Guards shall be provided for those portions of open-sided walking surfaces, including floors, stairs, ramps and landings that are located more than 30 inches measured vertically to the floor or grade below at any point within 36 inches horizontally to the edge of the open side. Required guards at open-sided walking surfaces, including stairs, porches, balconies or landings, shall be not less than 36 inches in height as measured vertically above the adjacent walking surface or the line connecting the nosings. Guards on the open sides of stairs shall have a height of not less than 34 inches. Where the top of the guard serves as a handrail on the open sides of stairs, the top of the guard shall be not less than 34 inches and not more than 38 inches. Guard openings from the walking surface to the required guard height shall not allow passage of a 4-inch sphere and the triangular openings at the open side of stairs formed by the riser, tread and bottom rail of a guard, shall not allow passage of a 6 inch sphere. Guards on the open side of stairs shall not have openings that allow passage of a 4 3/8 inch sphere. (R312)

Window fall protection must be provided for window openings less than 24 inches above the finished floor and more than 72 inches above grade or surface below on the exterior of the building. (R312.2) See the Boulder County Publication B32 Residential Stairways, Handrails, Ramps, and Guards, for more information. (IRC R312)

82. Bathtubs, walls above bathtubs with shower heads, shower floors, and shower compartments shall be finished with a non-absorbent surface which extends to a height not less than 6 feet above the floor. Showers must have a minimum 900 square inches of interior area and a minimum dimension in each direction of 30 inches and shall have a clear and unobstructed egress opening with a finished width of not less than 22 inches. Shower and tub/shower valves must be balanced-pressure/thermostatic valves and shall be equipped with a means to limit the valve to 120°F. Shower receptors shall have a curb threshold not less than 1 inch below the sides and back of the receptor. The curb shall measure a minimum of 2 inches to a maximum of 9 inches above the top of the drain. The finished floor shall have a 2% to 4% slope toward the drain. (IRC R307, P2708, P2709)
83. Smoke alarms shall be provided for new dwelling units and for existing dwellings when interior alterations, repairs, or additions requiring a permit occur and shall be located and installed per section R314. (IRC R314).

Carbon Monoxide alarms shall be provided for new dwelling units that contain a fuel-fired appliance or has an attached garage and shall be located and installed per section R315. Where alterations, repairs or addition requiring a permit occur, the individual dwelling unit shall be equipped with carbon monoxide alarms located as required for new dwellings except work involving the exterior surfaces of dwellings, such as the replacement of roofing or siding, or the addition or replacement of windows or doors, the addition of a porch or deck, or installation, alteration or repairs of plumbing and mechanical systems that are not fuel fired. (IRC R315).

Combination smoke and carbon monoxide alarms are permitted and can be used in lieu of either type of alarm. (IRC 314 & IRC 315).

84. EIFS exterior finish system installers must be certified and provide a copy of the ICBO required installation report to the Building Inspection Services prior to the final inspection (Evaluation Report).
85. All dwellings shall have a controlled method of water dispersal from roofs that will collect and discharge all roof drainage at least 5-feet from the foundation. Gutters, downspouts, downspout extensions shall be deemed adequate to meet these requirements. Surface drainage shall be diverted to a storm sewer conveyance or other approved point of collection so as to not create a hazard. Lots shall be graded so as to drain surface water away from foundation walls. The grade away from foundation walls shall fall a minimum of 6-inches within the first 10-feet. (IRC R401.3 and R801.3)
86. Site Plan Review requirements must be inspected and approved prior to final inspection approval of the building permit.
87. Provide a passive radon control system intended to resist entry and prepare the building for post-construction radon mitigation if necessary. (IRC Appendix AF)
88. Solar-Ready Provisions for new one- and two-family dwellings and townhouses – New residential buildings with not less than 600 square feet of roof area oriented between 110 degrees and 270 degrees of true north shall comply with the Colorado Model Electric Ready and Solar Ready Code and IRC Appendix AT Sections AT103.2 through AT103.8. Roof slopes that do not exceed 1:12 shall comply with AT103.6.
89. EV (electric vehicle) Readiness is required for new vehicle parking spaces for residential buildings with a detached garage or other onsite designated parking provided for the dwelling unit and shall comply with the Colorado Model Electric Ready, Solar Ready Code, and Appendix RD. One EV ready space shall be provided for each dwelling unit. (BCBCA Appendix RD and RV)

Each EV ready space shall have a branch circuit that complies with all of the following (BCBCA RV502.2):

1. Terminate at a receptacle, located within 3 feet of each EV ready space it serves. EV ready includes two adjacent parking spaces if the receptacle for the electrical facilities of this section is installed adjacent to and between both parking spaces.

1.1 Have a minimum circuit capacity of 8.3 kVA (40A 208/240V).

1.2 The electrical panel, electrical distribution equipment directory, and all outlets or enclosures shall be marked “For future electric vehicle supply equipment.”

Exception: A receptacle need not be provided if a hard-wired EVSE is installed.

This Publication is Printable