Student Discussion: The 2021 International Residential Code® (IRC®) Exam Study Course

Writing Assignment #6
What special concerns are addressed for pressure preservative treated wood basement floors and floors on ground? Pressure preservative treated wood basement floors and floors on ground present several special concerns and shall be designed to withstand axial forces and bending moments. One of such special concerns is unbalanced soil loads. Unless special provisions are made to resist sliding, wood basement floors shall be limited to applications where the differential depth of fill on opposite exterior foundation walls is 2 feet or less. Resistance to uplift or restraint against buckling shall also be addressed by interior bearing walls or stub walls anchored in the supporting soil below. Site preparation includes a minimum 4” thick granular base of gravel with a maximum ¾” crushed stone over compacted earth and a polyethylene sheeting with minimum 6-mil thickness placed over the granular base. The polyethylene membrane shall be placed over the wood sleepers and shall not extend beneath the footing plates of exterior walls.

Writing assignment #1.
Question: When there is a conflict between a general requirement and a specific requirement, which provision shall be applicable?
The specific requirement will always take precedent per R102.1

Writing assignment #2.
Question: What clearance is mandated between combustible insulation and recessed luminaires?
The mandated clearance between combustible insulation, recessed luminaires fan motors and other heat producing devices is 3 inches unless otherwise listed per R302.14

Writing assignment #3.
Question: What is the minimum required size of the largest habitable room in a dwelling unit?
The minimum required size of the largest habitable room in a dwelling unit is 70 square feet per R304.1. Most modern dwellings will not be close to this minimum amount of square footage, as typically the largest habitable room is much larger than 70 square feet.

Class 1 assignment:

When is a permit required? What types of work are exempted from permits?

A permit is required anytime an owner or owners authorized agent plans to construct, enlarge, alter, repair, move, demolish, or change the occupancy of a building or structure.

Works that are exempt are:

One-story detached accessory buildings where limited to 200 square feet in floor area (other than storm shelters)
• Fences not over 7 feet high
• Retaining walls not over 4 feet high
• Water tanks supported directly on grade, if the capacity does not exceed 5,000 gallons and the height to diameter ratio does not exceed 2 to 1
• Sidewalks and driveways
• Painting, papering, tiling carpeting, cabinets, counter tops and similar finish work
• Prefabricated swimming pools less than 24 inches deep
• Swings and other playground equipment
• Window awnings supported by an exterior wall that do not project more than 54 inches from the exterior wall
• Decks, if (1) 200 square feet maximum), (2) limited to 30 inches above grade, (3) not attached to a dwelling and (4) not serving the required exit door

Writing assignment #4.
Question: How is handrail height measured? What is the minimum height permitted? The maximum height? What sizes and shapes of handrails are acceptable?
Handrail height is measured vertically from the sloped plane adjoining the tread nosing or the finished surface of the ramp slope. The maximum height is 38 inches and a minimum of 34 inches. The only sizes and shapes that are acceptable are Type 1 and 2 handrails. Type 1 is 1-1/4 inch round minimum and 2 inch round maximum. The acceptable dimensional sizes of the various type 2 handrails can be found in R311.7.8.5 #2.

In reference to writing assignment #11

What are the installation requirements for clothes dryer exhaust systems? Exhaust ducts shall terminate on the outside of the building, shall be terminated in accordance with the dryer manufacturer’s installation instructions, if not specified in such instructions, the exhaust duct shall terminate not less than three feet in any direction from openings into buildings, including openings in vented soffits. Exhaust ducts shall be equipped with back draft damper, no screens permitted. What is the maximum length of a flexible transition duct? Eight feet. Where is such a duct permitted? Cannot be concealed within construction.

In reference to writing assignment #12

How far above the highest connected appliance outlet must a natural draft appliance vent terminate? Not less than 5 feet How far above the bottom of a wall vent must a natural draft gas vent terminate? Not less than 12 feet

Writing assignment #5.
Question: Under what conditions is an unvented crawl space permitted?
An unvented crawlspace is permitted under the provisions of Section R408.3. This addresses the construction methods which prevent the ventilation issues and keeping ambient moisture at a low enough level in the crawlspace where normal ventilation is not present.

Writing assignment #6
Question: What are the limitations for notches in floor joists? Bored holes?
Notches in joists shall not exceed one-sixth of the depth of the member, and shall not be longer than one-third of the depth of the member. They also shall not be located in the middle one-third of the span. Notches at the ends of the member shall not exceed one forth the depth of the member The tension side of members 4 inches or larger can only be notches at the ends.
Bored holes shall not exceed one-third of the depth of the member and cannot be closer than 2 inches from the top or bottom. Holes cannot also be closer than 2 inches to a notch.

Writing Assignment #14
What is the temperature limit for water supplied to a shower? A bathtub? A whirlpool bathtub? A bidet?

Showers, shower/tub combinations, and whirlpool tubs shall be equipped with a means to limit the maximum setting of the valve to 120 F which shall be field adjusted in accordance with the manufacturer’s specifications to provide water at a temperature not to exceed 120 F. The discharge water temperature from a bidet fitting shall be limited to not greater than 110 F.

  • When there is a conflict between a general requirement and a specific requirement, which provision shall be applicable?

When there is a conflict between a general requirement and a specific requirement then the specific requirement shall always govern

  • What is a dead load? A live load?

A live load refers to the weight that is not permanently fixed in a structure , such as people, furniture, or vehicles. Dead load, on the other hand, refers to the weight of the structure itself and any permanently attached elements, like walls, floors, and roofs.

  • Where must illumination be located in relationship to interior stairways? Exterior stairways?

Interior stairway capable of illuminating treads and landings of not less than 1 foot candle and a wall switch at top and bottom with 6 or more risers. Exterior stairway is light source at top and bottom of stairway.

  • How many egress doors from a dwelling are required? Under what conditions is an additional egress door required? What is the minimum required size of an egress door?

Not less than one egress door shall be provided for each dwelling unit. Provide a clear width of not less than 32 inches (813 mm) where measured between the face of the door and the stop

  • Under what conditions is an unvented crawl space permitted?

Class 1 vapor retarder with Joints of the vapor retarder shall overlap by 6 inches (152 mm) and shall be sealed or taped. , continuous mechanical exhaust, or air supply 1 cubic foot per minute, or a plenum, or a dehumidifier.

  • Can deck guard posts be notched?

It is now disallowed with the 2021 code update. 2021 IRC prohibits notching at the connection point when the post supports loads from the top and requires that the connection extends into the framing.

  • What is the criteria for the installation of weep screeds in exterior plaster applications?

Requires the weep screed with weep holes to be a minimum. The vertical attachment flange must be a minimum 3-1/2 inch and be placed at or below the foundation plate of the exterior stud wall.

  • What are the installation requirements for asphalt shingles?

Asphalt shingles shall be used only on 2:12 or greater. 2:12 to 4:12 shall have double underlayment .

  • What type of thermostat is required? How many thermostats must be provided?

For new buildings or when replacing existing thermostats, programmable thermostats are often required. These allow for scheduling temperature changes throughout the day, improving energy efficiency. Generally, at least one thermostat per HVAC system is required. For larger homes with multiple zones, each zone will need its own thermostat.

  • How high above a floor in a garage is an appliance with an ignition source required to be located?

    • The mechanical code requires appliances having an ignition source shall be elevated such that the source of ignition (spark) is not less than 18" above the floor of a garage
      Taking return air from a kitchen is not prohibited in a dwelling unit where the kitchen and living spaces are in a single room and the cooking appliance is electric and located not less than 5 feet (1524 mm) in any direction from the return air intake opening.
  • What is the maximum permitted length of a clothes dryer exhaust duct? How does the presence of one or more bends affect the allowable length?

The exhaust duct maximum length of the exhaust duct shall be 35 feet. Each bend shall shorten the length of the maximum length as stated in table: M1502.4.6.1

  • How far above the highest connected appliance outlet must a natural draft appliance vent terminate? How far above the bottom of a wall vent must a natural draft gas vent terminate?

A Type B or L gas vent shall terminate not less than 5 feet (1524 mm) in vertical height above the highest connected appliance draft hood or flue collar. A Type B-W gas vent shall terminate not less than 12 feet (3658 mm) in vertical height above the bottom of the wall furnace.

  • What methods are available for terminating a gas vent? Where are decorative shrouds permitted?

Gas vents that are 12 inches (304.8 mm) or less in size and located not less than 8 feet (2438.4 mm) from a vertical wall or similar obstruction. Gas vents that are over 12 inches (304.8 mm) in size or are located less than 8 feet (2438.4 mm) from a vertical wall or similar obstruction shall terminate not less than 2 feet (609.6 mm) above the highest point where they pass through the roof and not less than 2 feet (610 mm) above any portion of a building within 10 feet (3048 mm) horizontally.

Decorative shrouds shall not be installed at the termination of gas vents except where such shrouds are listed for use with the specific gas venting system and are installed in accordance with the manufacturer’s instructions.

  • What is the temperature limit for water supplied to a shower? A bathtub? A whirlpool bathtub? A bidet?

    • Limitation of Hot Water Temperature in Bathtubs and Whirlpool Bathtubs. The maximum hot water temperature discharging from the bathtub and whirlpool bathtub filler shall be limited to 120°F (49°C).
  • What special condition applies where a water heater having an ignition source is installed in a garage?

Water heaters having an ignition source shall be elevated such that the source of ignition is not less than 18 inches (457 mm) above the garage floor. Exception: Elevation of the ignition source is not required for appliances that are listed as flammable vapor ignition-resistant.

  • What fixtures are permitted to be vented by an island fixture venting system? Where is the connection to be located?

only sinks and lavatories are typically permitted to be vented by an island fixture venting system, and the connection should be made directly to the fixture drain, rising vertically above the drainage outlet before offsetting horizontally to connect to the vent pipe, which should be located above the flood level rim of the fixture being vented.

  • Where is bonding required to ensure electrical continuity? What methods of bonding are permitted?

Bonding is required wherever electrical continuity needs to be established between metallic components in an electrical system. this is usually achieved through connecting metal enclosures, raceways, and equipment together using bonding jumpers or conductors, which can be installed using methods like listed pressure connectors, exothermic welding, or terminal bars, depending on the application.

  • In what locations are arc-fault circuit interrupter protection mandated?

In bedrooms, living rooms, dining rooms, sunrooms, kitchens, laundry areas, closets, hallways, and family rooms.

Writing Assignment #15
What is the minimum permitted air gap for various fixtures? Where shall the critical level of an atmospheric-type vacuum breaker be set?
Lavatories and other fixtures with effective openings not greater than ½” in diameter, the minimum permitted air gap is 1” (away from a wall) or 1 ½” (close to a wall). Over-rim bath fillers and other fixtures with effective openings not greater than 1” in diameter, the minimum permitted air gap is 2” (away from a wall) or 3” (close to a wall). Sink, laundry trays, gooseneck back faucets and other fixtures with effective openings not greater than ¾” in diameter, the minimum permitted air gap (away from a wall) is 1.5” and 2.5” (close to a wall). Away from a wall measurements are applicable where walls or obstructions are spaced from the nearest inside edge of the spout opening a distance greater than three times the diameter of the effective opening for a single wall, or a distance greater thatn four times the diameter of the effective opening for two intersecting walls. For atmospheric-type vacuum breakers, the critical level shall be set at not less than 6” above the highest elevation of downstream piping and the flood level rim of the fixture or device.
Writing Assignment #16
How are air admittance valves regulated? Where are such valves permitted? Where should they be located?
Individual and branch-type air admittance valves shall conform to ASSE 1051. Stack-type air admittance valves shall conform to ASSE 1050. The valves shall be installed in accordance with Section P3114 and the manufacturer’s instructions, shall provide access and shall be installed in a location that allows air to enter the valve. Air admittance valves shall only be installed after the DWV testing required by P2503.5.1 or P2503.5.2 has been performed.
Individual vents, branch vents, circuit vents and stack vents shall be permitted to terminate with a connection to an air admittance valve. Individual and branch-type air admittance valves shall vent only fixtures that are on the same floor level and connect to a horizontal branch drain. Individual and branch air admittance valves shall be located not less than 4” above the horizontal branch drain or fixture drain being vented. Stack-type air admittance valves shall be located not less than 6” above the flood level rim of the highest fixture being vented. The valve shall be located within the maximum developed length permitted for the vent. The valve shall be installed not less than 6” above insulation materials where installed in attics.

Writing assignment #7.
Question: Where must a bored hole in a stud be located? What is the maximum permitted size of a bored hole located in a bearing wall? In a nonbearing wall?
A bored hole in a stud cannot be located in the the same section of a notch or cut. The maximum size of a bored hole is limited to 60% of the stud width in an exterior wall and the stud must be double if over 40%. The bored hole cannot be over 40% at an interior wall.

Writing assignment #8.
Question: How must roof drainage water be discharged?
Roof drainage water shall discharge a minimum of 5 feet from the foundation walls or into an approved drainage system.
Unless roofs are sloped to drain over roof edges, roof drains shall be installed at each low point in the roof.

Writing Assignment #17

Where must the service disconnecting means be located? What is the maximum number of disconnects?

Service disconnects shall be provided and shall be permanently marked as a service disconnect. The service disconnecting means shall be installed at a readily accessible location either outside of a building or inside nearest the point of entrance of the service conductors. Service disconnecting means shall not be installed in bathrooms. Each service shall have only one disconnecting means unless installed using one or more of the methods specified in E3601.7.1 through E3601.7.3. In all cases, the maximum number of disconnecting means for any service shall not exceed six and the multiple service disconnecting means shall be grouped.

Writing assignment #9.
Question: At what minimum height is a masonry chimney required to terminate?
A masonry chimney is required to terminate a least 3 feet above the roof surface and also 2 feet higher that any roof surface within 10 horizonal feet. This helps prevent the possibility of downward drafts creating eddying near the chimney termination.

Writing assignment #10
Question:
How high above a floor in a garage is an appliance with an ignition source required to be located?
An appliance with an ignition source is required to be 18 inches above the garage floor. This clearance is intended to be high enough above any fumes that can be present in a garage from spilled gasoline or other combustibles.

Writing Assignment #18

In what locations are arc-fault circuit interrupter protection mandated?

E3902.17. Branch circuits that supply 120-volt, single phase, 15- and 20-ampere outlets installed in kitchens, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, laundry areas and similar rooms or areas shall be protected by:

  • A listed combination type arc fault circuit interrupter, installed to provide protection of the entire branch circuit; or
  • A listed branch/feeder type AFCI installed at the origin of the branch circuit in combination with a listed outlet branch-circuit-type arc fault circuit interrupter installed at the first outlet box on the branch circuit. The first outlet box in the branch circuit shall be marked to indicate that it is the first outlet of the circuit; or
  • A listed supplemental arc-protection circuit breaker installed at the origin of the branch circuit in combination with a listed outlet branch-circuit-type arc fault circuit interrupter installed at the first outlet box on the branch circuit where all of the following conditions are met:
    3.1The branch-circuit wiring shall be continuous from the branch-circuit overcurrent device to the outlet branch-circuit arc-fault circuit interrupter.

3.2The maximum length of the branch-circuit wiring from the branch-circuit overcurrent device to the first outlet shall not exceed 50 feet (15.2 m) for 14 AWG conductors and 70 feet (21.3 m) for 12 AWG conductors.

3.3The first outlet box on the branch circuit shall be marked to indicate that it is the first outlet on the circuit. [210.12(A)(3)]

A listed outlet branch-circuit-type arc-fault circuit interrupter installed at the first outlet on the branch circuit in combination with a listed branch-circuit overcurrent protective device where all of the following conditions are met:

4.1The branch-circuit wiring shall be continuous from the branch-circuit overcurrent device to the outlet branch-circuit arc-fault circuit interrupter.

4.2The maximum length of the branch-circuit wiring from the branch-circuit overcurrent device to the first outlet shall not exceed 50 feet (15.2 m) for 14 AWG conductors and 70 feet (21.3 m) for 12 AWG conductors.

4.3The first outlet box on the branch circuit shall be marked to indicate that it is the first outlet on the circuit.

4.4The combination of the branch-circuit overcurrent device and outlet branch-circuit AFCI shall be identified as meeting the requirements for a system combination-type AFCI and shall be listed as such. [210.12(A)(4)]

Writing Assignment #11
Question:
What is the maximum permitted length of a clothes dryer exhaust duct? How does the presence of one or more bends affect the allowable length?
The maximum length of a clothes dryer duck is 35 feet. The presence of bend will restrict the airflow. The calculations to determine how each 45 or 90 degree bend in the ductwork can be found in Table M1502.4.6.1