CODES

ADOPTS WITH AMENDMENTS:

International Residential Code 2009 (IRC 2009)

Copyright

Preface

Effective Use of the International Residential Code

Ordinance

Chapter 1 Scope and Administration

Chapter 2 Definitions

Chapter 3 Building Planning

Chapter 4 Foundations

Chapter 5 Floors

Chapter 6 Wall Construction

Chapter 7 Wall Covering

Chapter 8 Roof-Ceiling Construction

Chapter 9 Roof Assemblies

Chapter 10 Chimneys and Fireplaces

Chapter 11 Energy Efficiency

Chapter 12 Mechanical Administration

Chapter 12 Mechanical Administration

Chapter 13 General Mechanical System Requirements

Chapter 13 General Mechanical System Requirements

Chapter 14 Heating and Cooling Equipment

Chapter 14 Heating and Cooling Equipment

Chapter 15 Exhaust Systems

Chapter 15 Exhaust Systems

Chapter 16 Duct Systems

Chapter 16 Duct Systems

Chapter 17 Combustion Air

Chapter 17 Combustion Air

Chapter 18 Chimneys and Vents

Chapter 18 Chimneys and Vents

Chapter 19 Special Fuel-Burning Equipment

Chapter 19 Special Fuel-Burning Equipment

Chapter 20 Boilers and Water Heaters

Chapter 20 Boilers and Water Heaters

Chapter 21 Hydronic Piping

Chapter 21 Hydronic Piping

Chapter 22 Special Piping and Storage Systems

Chapter 22 Special Piping and Storage Systems

Chapter 23 Solar Systems

Chapter 23 Solar Systems

Chapter 24 Fuel Gas

Chapter 24 Fuel Gas

Chapter 25 Plumbing Administration

Chapter 25 Plumbing Administration

Chapter 26 General Plumbing Requirements

Chapter 26 General Plumbing Requirements

Chapter 27 Plumbing Fixtures

Chapter 27 Plumbing Fixtures

Chapter 28 Water Heaters

Chapter 28 Water Heaters

Chapter 29 Water Supply and Distribution

Chapter 29 Water Supply and Distribution

Chapter 30 Sanitary Drainage

Chapter 30 Sanitary Drainage

Chapter 31 Vents

Chapter 31 Vents

Chapter 32 Traps

Chapter 32 Traps

Chapter 33 Storm Drainage

Chapter 33 Storm Drainage

Chapter 34 General Requirements

Chapter 34 General Requirements

Chapter 35 Electrical Definitions

Chapter 35 Electrical Definitions

Chapter 36 Services

Chapter 36 Services

Chapter 37 Branch Circuit and Feeder Requirements

Chapter 37 Branch Circuit and Feeder Requirements

Chapter 38 Wiring Methods

Chapter 38 Wiring Methods

Chapter 39 Power and Lighting Distribution

Chapter 39 Power and Lighting Distribution

Chapter 40 Devices and Luminaires

Chapter 40 Devices and Luminaires

Chapter 41 Appliance Installation

Chapter 41 Appliance Installation

Chapter 42 Swimming Pools

Chapter 42 Swimming Pools

Chapter 43 Class 2 Remote-Control, Signaling and Power-Limited Circuits

Chapter 43 Class 2 Remote-Control, Signaling and Power-Limited Circuits

Chapter 44 Referenced Standards

Chapter 45 HIGH WIND ZONES

Chapter 46 COASTAL AND FLOOD PLAIN CONSTRUCTION STANDARDS

Appendix A Sizing and Capacities of Gas Piping

Appendix B Sizing of Venting Systems Serving Appliances Equipped With Draft Hoods, Category I Appliances, and Appliances Listed for Use With Type B Vents

Appendix C Exit Terminals of Mechanical Draft and Direct-Vent Venting Systems

Appendix D Recommended Procedure for Safety Inspection of an Existing Appliance Installation

Appendix E Manufactured Housing Used as Dwellings

Appendix F Radon Control Methods

Appendix G Swimming Pools, Spas and Hot Tubs

Appendix H Patio Covers

Appendix I Private Sewage Disposal

Appendix J Existing Buildings and Structures

Appendix K Sound Transmission

Appendix L Permit Fees

Appendix M Home Day Care - R-3 Occupancy

Appendix M WOOD DECKS

Appendix N Venting Methods

Appendix N BASIC LOAD ESTIMATING

Appendix O Gray Water Recycling Systems

Appendix O FOAM PLASTIC DIAGRAMS

Appendix P Sizing of Water Piping System

Appendix P DWELLING UNIT FIRE SPRINKLER SYSTEMS

Appendix Q ICC International Residential Code Electrical Provisions/National Electrical Code Crossreference

Appendix Q DISCONTINUOUS FOOTING DETAIL FOR GARAGE OR PORCH WALLS FOUNDATION WALL EXTENSION DETAIL

Chapter 45 HIGH WIND ZONES

STATE AMENDMENT
This chapter is a North Carolina addition to the 2009 International Residential Code. There will be no underlined text.

Section R4501 GENERAL

STATE AMENDMENT

R4501.1 General

STATE AMENDMENT
The provisions of this chapter shall be applicable to buildings constructed in high wind zones as noted by the text. These provisions shall be in addition to or in lieu of previous chapters.
In lieu of specific code requirements for structures in the 110, 120, and 130 miles per hour wind (48 m/s, 53 m/s and 57m/s) zones, compliance with International Code Council ICC 600-2008 Standard for Residential Construction in High-Wind Regions or AF&PA Wood Frame Construction Manual for One- and Two-Family Dwellings is acceptable.
TABLE R4502(a)
DESIGN PRESSURES FOR DOORS AND WINDOWSa, b, c, d
POSITIVE AND NEGATIVE IN PSF
VELOCITY
(mph)
MEAN ROOF HEIGHT (ft)
15 25 35e
110 25 29 32
120 31 35 39
130 37 43 47
For SI: 1 foot = 304.8 mm, 1 mile per hour = 0.R45 m/s, 1 degree = 0.01745 rad.
  1. Alternate pressures may be determined by using the North Carolina Building Code, ASCE-7, or the International Building Code.
  2. If window or door is more than 4 feet from a corner, the pressure from this table shall be permitted to be multiplied by 0.87. This adjustment does not apply to garage doors.
  3. For windows or doors in structures with a roof slope of 10 degrees (2:12) or less from the horizontal, the pressure from this table may be multiplied by 0.90.
  4. Design pressure ratings based on the standards listed in Section R613 are adequate documentation of capacity to resist pressures from the table.
  5. Where the mean roof height exceeds this table, values shall be determined by a design professional.


TABLE R4502(b)
DESIGN PRESSURES (IN PSF) GARAGE DOORSa, b, c, d, e
VELOCITY
(mph)
MEAN ROOF HEIGHT (ft)
15 25 35f
110 20 23 26
120 25 29 32
130 30 35 39
For SI: 1 foot = 304.8 mm, 1 mile per hour = 0.R45 m/s, 1 degree = 0.01745 rad.
  1. The pressures in this table are for garage doors at least 9 feet by 7 feet and at least 2 feet from the corner.
  2. Alternate design pressures may be determined by using the North Carolina Building Code, ASCE-7, or the International Building Code.
  3. For doors in a structure with a roof slope of 10 degrees (2:12) or less from the horizontal the pressures from this table may be multiplied by 0.90.
  4. Design pressure ratings based on tests done according to ASTM E330 are adequate documentation.
  5. Garage doors on the ground level of a structure in a flood zone do not have to meet the above design pressures provided all of the following conditions are met:

    1. Structure is anchored to the girders and top of the piling to resist the forces given in Chapter R45.
    2. The garage door occurs below the top of the piling.
    3. Provide openings at the garage level that comply with either of the following options:

      1. Design all exterior walls at the garage level to break away at 20 psf or less or;
      2. Provide openings (in walls at the garage level without the garage level without the garage door) equal to at least 20 percent of the total wall area from the ground to the roof.
  6. Where the mean roof height exceeds this table, values shall be determined by a design professional.

Section R4503 FOOTINGS

STATE AMENDMENT
Foundation wall footings in the 120 and 130 mph (53 m/s and 57 m/s) wind zones shall be a minimum of 8 inches by 24 inches (203 mm by 610 mm) for houses 2½ stories and less. The footing for a three-story building shall be 10 inches by 24 inches (254 mm by 610 mm). Footings shall be reinforced with three #4 (or two #5 bars) at 3 inches (76 mm) above the bottom of the footing. The bars shall be continuous or lapped 25 inches (635 mm) at all splices.
The curtain wall footing must meet the minimum projection requirements in Figure R403.1(1) and footing dimensions for the pier footings shall comply with Table R4503.2.1.

TABLE R4503.2.1
FOOTINGS TO RESIST UPLIFT FROM PIERS IN 120 AND 130 MPH WIND ZONES SUPPORTING GIRDERS IN EXTERIOR WALLS
FOOTING SIZE
GIRDER SPAN
VELOCITY
(mph)
4'-0" 6'-0" 8'-0"
120 2'-0" x 2'-0" x 10" 2'-4" x 2'-4" x 10" 2'-8" x 2'-8" x 12"
130 3'-0" x 3'-0" x 10" 3'-4" x 3'-4" x 12" 3'-8" x 3'-8" x 12"
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.R45 m/s. Note: See Table R403.1a for 110 mph.
Uniform continuous width footings for pier and curtain wall foundations shall be a minimum of 8 inches (203 mm) thick and 24 inches (60 mm) wide. Footings shall be reinforced with three #4 bars (or two #5 bars) at 3 inches (76 mm) above the bottom of the footing. The bars shall be continuous or lapped 25 inches (635 mm) at all splices.

R4503.3 Footing dowels

STATE AMENDMENT
All footings shall have dowels to match reinforcing in the foundation wall or pier above (see Sections R4504.1.1 and R4504.3). Dowels shall have a standard hook length of 12 times the bar diameter embedded in the footing and shall lap the wall or pier reinforcing at least 25 inches (635 mm).

R4504.1 Anchorage

STATE AMENDMENT
Exterior walls of structures in the 120 and 130 mph (53 m/s and 57 m/s) wind zones shall be anchored to the footing to resist the forces specified in Section R4508.2, by the prescriptive requirements of this section, or as allowed by Section R4508.4 and Figures R4504.3(a) through R4504.3(d). Exterior walls of structures in the 110 mph (53 m/s) wind zone shall be anchored to the foundation wall, pier/curtain wall, or slab on grade with 1/2-inch (13 mm) anchor bolts, 4 feet (1219 mm) on center extended 15 inches (381 mm) into masonry and 7 inches (178 mm) into concrete and are exempt from the requirements of this section.

TABLE R4504.1
STRUCTURAL ANCHORAGEa
WIND SPEED (mph) 120 130
MAXIMUM SPACING (inches) 21 18
For SI: 1 inch = 25.4 mm, 1 mile per hour = 0.R45 m/s.
  1. Required spacing of 1/2-inch anchor bolts where a bond beam is required and for slab on grade with a single sole plate. [See Figure R403.1(1) for 110 mph or less.]

For SI: 1 inch = 25.4 mm.
FIGURE R4504.3(a)
CONTINUOUS VENEER PIER/CURTAIN WALL

For SI: 1 inch = 25.4 mm.
FIGURE R4504.3(b)
CONTINUOUS VENEER PIER/CURTAIN WALL

For SI: 1 inch = 25.4 mm.
FIGURE R4504.3(c)
VENEER SHIRT WALL PIER/CURTAIN WALL

For SI: 1 inch = 25.4 mm.
FIGURE R4504.3(d) VENEER SHIRT WALL PIER/CURTAIN WALL
Vertical reinforcement shall be installed not more than 2 feet (51 mm) from each corner at intervals not to exceed Table R4504.1.1 with all reinforced cells grouted and shall either terminate in a bond beam or connect to the wall above.

TABLES R4504.1.1
WALL REINFORCEMENT OR CONTINUOUS ANCHORAGEa, b, c, d
BAR/BOLT SIZE (inches) 58 12 38
MAXIMUM SPACING (inches) 96 72 42
For SI: 1 inch = 25.4 mm.
  1. Applies to 120 and 130 mph wind zones.
  2. Continuous anchorage from footing to girder or wall framing.
  3. Applies to footing dowel bars, vertical reinforcement and anchor bolts.
  4. Spacing may exceed the tabulated values by up to 8 inches provided the total number of required bars is installed.

R4504.1.2

STATE AMENDMENT
An 8 inch x 8 inch (203 x 203 mm) concrete or CMU bond beam with one #5 bar shall be used at the floor level. The bar shall be continuous or lapped 25 inches (635 mm) at all splices.

Exception: The bond beam may be eliminated where the uplift connectors are continuous from the footing to the exterior wall framing and the rim band is continuous (doubled or adequately spliced).

R4504.2 Sill plates

STATE AMENDMENT
A minimum 2 x 6 sill plate shall be installed.

Exception: Where the uplift connectors are continuous from the footing to the exterior wall framing.

R4504.2.1

STATE AMENDMENT
Sill plates shall be anchored with 1/2-inch (13 mm) anchor bolts with 2 x 2 x 1/8 inch (51 x 51 x 3 mm) washers at intervals not to exceed Table R4504.1. Where the vertical reinforcement bars/bolts terminate at the sill plate with a connector capable of developing the bar/bolt capacity, approved strap anchors from the sill plate to the wall framing shall be installed (Note: Cable clamps have no rated capacity when used with reinforcing steel or bolts).

Exception: Where the uplift connectors are continuous from the footing to the exterior wall framing, the spacing of the continuous anchorage may be increased in accordance with Table R4504.1.1.
Vertical reinforcement shall be installed not more than 2 feet (51 mm) from each corner at intervals not to exceed Table R4504.1.1 with all reinforced cells grouted and shall connect to all sill plates, to the exterior girder, or to the wall above [see Figures R4504.3(a) through R4504.3(d)].

R4504.3.1

STATE AMENDMENT
Where the vertical reinforcement bars terminate at the sill plate, a minimum 2 x 6 sill plate and approved strap anchors from the sill plate to the wall framing shall be installed.

R4504.3.2

STATE AMENDMENT
Two #4 footing dowel bars shall be embedded into the footing and grouted to the top of each pier. If the vertical reinforcement bars are placed inside the piers (not between the pier/curtain wall), then one footing dowel bar may be omitted from each pier.
Vertical reinforcement shall be installed at intervals not to exceed Table R4504.1.1 and shall terminate in a double sole plate.

Exception: Vertical reinforcement (anchorage) shall be installed at intervals not to exceed Table R4504.1 where the bars terminate in a single sole plate. Approved strap anchors or wood structural panels shall be installed to provide a continuous load-path from the single sole plate to the wall.

R4505.1 Construction

STATE AMENDMENT
Exterior walls of wood frame construction shall be in accordance with Figures R602.3(1) and R602.3(2). Components of exterior walls shall be fastened in accordance with Table R602.3(1). Walls of wood frame construction shall be designed and constructed in accordance with AF&PA “National Design Specifications for Wood Construction,” listed in Chapter 44.

     Exterior walls subject to wind pressures of 110 mph (48 m/s) or greater as established in Table R301.2(1) shall be designed in accordance with accepted engineering practice [such as Tables R4505(a) and R4505(b)].

     In bearing walls, studs which are not more than 10 feet (3048 mm) in length shall be spaced not more than is specified in Tables R4505(a) and R4505(b) for the corresponding stud size.

TABLE R4505(a)
STUDS IN 110, 120, AND 130 MPH ZONES

Requirements for Wood Stud In: Exterior Walls Supporting One Floor, Roof and Ceiling or Less/ Exterior Nonloadbearing Walls in Two Story Structure or Less/Interior Walls Supporting One Floor, Roof and Ceiling or Less
110 MPH 110 MPH 120 MPH 130 MPH
STUD LENGTH STUD SPACING 2x4 2x6 2x4 2x6 2x4 2x6 2x4 2x6
8 16 Species: Spruce Pine Fir (South) without Structural Sheathing Species: Spruce Pine Fir (South) with 38" Wood Structural Sheathing
#2 Stud Stud Stud Stud Stud #2 Stud
8 24 #2 Stud #2 Stud #2 Stud #2 Stud
10 16 #2 Stud #2 Stud #2 Stud #2 Stud
10 24 Design #2 Design #2 Design #2 Design #2
Species: Spruce Pine Fir without Structural Sheathing Species: Spruce Pine Fir (South) with 38" Wood Structural Sheathing
8 16 Stud Stud Stand Stud Stud Stud #3 Stud
8 24 #2 Stud #3 Stud #2 Stud #2 Stud
10 16 #2 Stud #2 Stud #2 Stud #2 Stud
10 24 Design Stud #2 Stud Design Stud Design Stud
Species: Southern Pine without Structural Sheathing Species: Southern Pine with 38" Wood Structural Sheathing
8 16 Stud Stud Stand Stud Stud Stud Stud Stud
8 24 #2 Stud Stud Stud #2 Stud #2 Stud
10 16 #2 Stud Stud Stud #2 Stud #2 Stud
10 24 Design Stud #2 Stud #2 Stud Design Stud
For SI: 1 inch = 25.4 mm, 1 mile per hour = 0.R45 m/s.
Explanation of Table Entries:
Design – Studs with this entry shall be in accordance with accepted engineering practice.
#2 – #2 Grade construction
#3 – #3 Grade
Stud – Stud grade
Standard – Standard grade
Utility – Utility grade
38" wood structural sheathing shall be attached with 8 D nails at 6" at perimeter and 12" at intermediate supports. When a grade is specified in the table any grade above it in this list may be used.


TABLE R4505(b)
EXTERIOR BEARING WALLSa,b,c,d,e FIRST FLOOR OF THREE STORY
PSF SP
WIND ZONE (mph) 2x4 @ 12" oc
Structural Sheathing
3x4 or 2x6 @ 16" oc
Structural Sheathing
2x4 @ 12" oc
Structural Sheathing
3x4 or 2x6 @ 16" oc
Structural Sheathing
110 #2 Any grade Any grade Any grade
120 #2 Any grade #2, #3, Stud Any grade
130 #2 Any grade #2, #3, Stud Any grade
Exterior Nonbearing Wallsa, b, c, d, e, f First Floor of Three Story
WIND ZONE (mph) 2x4 @ 12" oc Blocking 2x4 @ 16" oc Blocking 3x4 or 2x6 @ 16" oc Blocking 2x4 @ 12" oc Blocking 2x4 @ 16" oc Blocking 3x4 or 2x6 @ 16" oc Blocking
110 #2, Stud #2 Any grade Any grade #2, #3, Stud Any grade
120 #2, Stud NP Any grade #2, #3, Stud #2, #3 Stud Any grade
130 #2 NP Any grade #2, #3, Stud #2 Any grade
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
  1. Any grade = any grade except standard, utility and economy.
  2. Corner bracing is REQUIRED where “Blocking” is specified.
  3. 2 – 2x4s at 16 inches or 1 – 2x4 at 8 inches may be used where 3x4 at 16 inches is specified.
  4. Refer to Sections R4506 and R4508.4 for sheathing requirements.
  5. Bearing stud height is limited to 10 feet.
  6. 2x full depth blocking at mid-height.
  1. When the wall studs are engineered and do not require structural sheathing, for one story or top story – brace each corner and at 25-foot (7620 mm) intervals with 1 x 4 let-in bracing or 4 foot x 8 foot (1219 x 2438 mm) wood structural panels.
  2. All other stories – wood structural sheathing panels.
  3. See also Section R602.10.
All stories – wood structural sheathing panels. Blocking shall be installed if less than 50 percent of the wall length is sheathed. Where blocking is required, all panels shall be fastened at 3 inches (76 mm) on center along the edges and 6 inches (152 mm) on center at intermediate framing. If a wall is sheathed less than 25 percent of its length, then that wall shall be designed in accordance with approved engineering practice. See also Section R602.10.

R4506.3 Gable endwalls

STATE AMENDMENT
Gable endwalls in the 110, 120 and 130 mph (48 m/s, 53 m/s and 57 m/s) wind zones shall either be supported by lateral bracing at the ceiling or have continuous studs from the floor to the roof. 2 x 4 studs at 16 inches (406 mm) on center are limited to 10 feet (3048 mm) in length between supports. Nonbearing 2 x 6 SPF#2 studs at 16 inches (406 mm) on center with 38-inch (9 mm) wood structural panel sheathing are limited to unsupported lengths of 18 feet (5486 mm) in 110 mph (48 m/s), 16 feet (4877 mm) in 120 mph (53 m/s) and 14 feet (4267 mm) in 130 mph (57 m/s) wind zones. Wood structural panel sheathing shall extend 12 inches (305 mm) beyond horizontal construction joints except where the horizontal joint occurs over minimum 1 inch (25 mm) thick OSB or plywood rimboard with a minimum 1-½ inch (38 mm) overlap.
Where studs are not continuous, the ceiling must be used to support the endwall. 2 x 4 lateral bracing shall be installed on the top of ceiling joists or truss bottom chords at 8 feet (2438 mm) on center and extend 8 feet (2438 mm) inward from the gable endwall. See Figure R4506.7(a).

For SI: 1 inch = 25.4 mm.
FIGURE R4506.7(a)
OVERHANG AT ENDWALLS

For SI: 1 inch = 25.4 mm.
FIGURE R4506.7a—continued
OVERHANG AT ENDWALLS

R4506.5 Full height studs

STATE AMENDMENT
Full height studs may be sized using the bracing at the ceiling to limit the stud length. See Figure R4506.5.

For SI: 1 inch = 25.4 mm.
FIGURE R4506.5
GABLE ENDWALL BALLOON FRAMING PREFERRED METHOD

R4506.6 Cathedral endwalls

STATE AMENDMENT
Studs shall be continuous from the uppermost floor to either the ceiling or the roof.
The overhang is limited to 12 inches (305 mm) where a laddered soffit is installed. The overhang may be increased to 24 inches (610 mm) where outlookers are framed over a dropped endwall into the first rafter or truss. See Figure R4506.7(a) and R4506.7(b). If the overhang exceeds 24 inches (610 mm), then the overhang shall be designed in accordance with approved engineering practice.

For SI: 1 inch = 25.4 mm.
FIGURE R4506.7b
GABLE END OVERHANG

FIGURE R4506.7(c)
GABLE END OVERHANG
The roof sheathing panel edges shall be blocked and nailed at the end two rafter or truss spaces. See Figure R4506.8.

Exception: The panel edges need not be blocked where 2 x 4 diagonal braces are framed from the top of the endwall to the lateral bracing at the ceiling.

FIGURE R4506.8
ROOF SHEATHING ATTACHMENT PLAN

R4507.1 Reinforcement

STATE AMENDMENT
Masonry walls subject to wind loads of 120 mph (53 m/s) or greater, as established in Table R301.2(1), shall be constructed in accordance with Table R4507.1a or R4507.1b or the requirements of Figures R4507.1(a) and R4507.1(b) and this section. Additionally, the minimum area of reinforcement shall not be less than 0.002 times the gross cross-sectional area wall, not more than two-thirds of which may be used in either direction. No required vertical reinforcement shall be less than 3/8 inch (9.5 mm) in diameter. Principal wall reinforcement shall have a maximum spacing of 4 feet (1219 mm) on center.

Note: For 110 mph (48 m/s) wind zones, see Figure 606.11(1) and Table 606.9.

TABLE R4507.1a
H/T LATERAL SUPPORT RATIOS FOR UNREINFORCED EXTERIOR MASONRY WALLSa,b,d,e
OTHER THAN ENCLOSED BUILDINGS3 DESIGN WIND SPEED, MPH
Wall construction 120 130
Solid masonry units 13 11
Hollow concrete masonry units or masonry bonded hollow walls 9 8
Cavity walls identical wythes The H/t ratio shall be 0.70 of the H/t ratio for single wythe walls. The t-value shall be the sum of the nominal thickness of the individual wythes.
Cavity walls with wythes of different types or size masonry The wall shall be designed based on ACI-530 or the H/t ratio may be 0.70 of the H/t ratio of a single wythe hollow wall. The t-value shall be the sum of the nominal thickness of the individual wythes.
  1. H = clear height or length between lateral supports.
    t = nominal wall thickness.
  2. All masonry units shall be laid in Type M, S or N mortar. Where Type N mortar is used and the wall spans in the vertical direction, the ratios shall be reduced by 10 percent.
  3. Design based on partially enclosed building.
  4. These values are based on using masonry cement mortar. If nonair-entrained Portland cement/lime mortar is used the values in the table may be increased by 1.25. Larger H/t ratios may be used if the design is done in accordance with ACI-530.
  5. Larger H/t ratios may be used if the design is done in accordance with ACI-530.


TABLE R4507.1b
H/T LATERAL SUPPORT RATIOS FOR UNREINFORCED EXTERIOR MASONRY WALLSa,b,d,e
OTHER THAN ENCLOSED BUILDINGSc DESIGN WIND SPEED, MPH
Wall construction 120 130
Solid masonry units 15 13
Hollow concrete masonry units or masonry bonded hollow walls 10 9
Cavity walls identical wythes The H/t ratio shall be 0.70 of the H/t ratio for single wythe walls. The t-value shall be the sum of the nominal thickness of the individual wythes.
Cavity walls with wythes of different types or size masonry The wall shall be designed based on ACI-530 or the H/t ratio may be 0.70 of the H/t ratio of a single wythe hollow wall. The t-value shall be the sum of the nominal thickness of the individual wythes.
  1. H = clear height or length between lateral supports. t = nominal wall thickness.
  2. All masonry units shall be laid in Type M, S or N mortar. Where Type N mortar is used and the wall spans in the vertical direction, the ratio shall be reduced by 10 percent.
  3. Enclosed buildings are buildings in which the openings in any wall do not exceed the sum of the percentages of openings in the remaining walls and roof surfaces by 5 percent. Buildings in which the 5 percent limit is exceeded by one wall may still be considered enclosed if the percentage of openings in no other wall exceeds 20 percent.
  4. These values are based on using masonry cement mortar. If nonair-entrained Portland cement/lime mortar is used the values in the table may be increased 1.2.
  5. Larger H/t ratios may be used if the design is done in accordance with ACI-530.


For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 psf = 0.0479 kN/m2.
FIGURE R4507.1(a)
REQUIREMENTS FOR REINFORCED GROUTED MASONRY CONSTRUCTION WHERE WIND ZONES ARE 120 MPH OR GREATER

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 psf = 0.0479 kN/m2.
FIGURE R4507.1(b)
REQUIREMENTS FOR REINFORCED HOLLOW-UNIT MASONRY CONSTRUCTION WHERE WIND ZONES ARE 120 MPH OR GREATER

Section R4508 ROOF TIE DOWN

STATE AMENDMENT

R4508.1 Roof tie down

STATE AMENDMENT
Roof assemblies in the 110, 120 and 130 mph (48 m/s, 53 m/s and 57 m/s) wind zones as established in Table 301.2(1) shall have rafter or truss ties provided in accordance with either Table R4508.2 or the prescriptive requirements of this Section R4508. Anchorage in the 110 mph (48 m/s) wind zone shall be continuous from the roof to the foundation wall or pier. Anchorage in the 120 and 130 mph (53 m/s and 57 m/s) wind zones shall be continuous from the roof to the footing (see Section R4504.1).

TABLE R4508.2
ROOF TIE DOWN REQUIREMENTS ALONG EXTERIOR WALLS (plf)a,b,c,d
WIND SPEED (mph) STRUCTURE WIDTH
24 feet 36 feet
110 240 345
120 330 470
130 430 615
For SI: 1 foot = 304.8 mm, 1 mile per hour = 0.R45 m/s.
  1. Alternate to the requirements of this table or roof not covered by this table shall be designed in accordance with the North Carolina State Building Code or SSTD10, “Standard for Hurricane Resistant Residential Construction.”
  2. See Section 4505 for material requirements in Coastal High Hazard Areas and Ocean Hazard Areas and Ocean Hazard Areas.
  3. Roof slope 2:12 to 12:12.
  4. The uplift load requirements may be interpolated for intermediate structure widths.

R4508.2 Considerations

STATE AMENDMENT
For trusses, the nailing requirements from Table R4508.2 shall include the nailing requirements for both rafters and ceiling joists. As an alternative to the anchorage requirements of Tables 602.3(1) and R4508.2, the anchorage for roof members may be based on a designed connection taking into account all horizontal and vertical forces. Forces for alternative anchorage design may result from wind uplift; wind lateral on roof; wind lateral on walls to be transferred to the top plate of the wall; roof/ceiling loads; and other loads depending on the specific building design. If roof members align with the studs, the connection may be made from the roof member directly to the studs. If the connection is from the roof member to the top plate, a double top plate is required and both connections must meet the requirements of Table R4508.2. Where ceiling joists are not parallel with and connect to the roof members, the anchorage requirements for each roof member shall be increased by 110 pound (50 kg). Hip end walls and hip rafters shall be anchored in accordance with this section.
One and one-half inch (38 mm) by 18 gage fabricated metal ties at 24 inches (610 mm) on center with five 8d nails at each end may be used to resist the uplift loads from the roof to the double top plate. Install one tie at each end of each rafter in 110 mph (48 m/s) and two ties at each end of each rafter in 120 mph (53 m/s) and 130 mph (57 m/s) wind zones. Truss anchorage shall be per designed specifications.
Wood structural panel sheathing may be used to resist both lateral load and uplift simultaneously. Panels shall be installed as follows:
  1. Panels may be installed with face grain parallel or perpendicular to studs.
  2. Panels shall be 38-inch (10 mm) minimum thickness.
  3. Nail spacing shall be 8d at 6 inches (152 mm) on center along vertical edges of panel and 12 inches (305 mm) at intermediate vertical framing.
  4. Horizontal nail spacing at double row of 8d staggered at 3 inches (76 mm) on center.
  5. Panel shall extend 12 inches (305 mm) beyond horizontal construction joints and shall overlap girders their full depth except where the horizontal joint occurs over minimum 1 inch (25 mm) thick OSB or plywood rimboard with a minimum 1-12 inch (38 mm) overlap.
  6. Panel attachment to framing shall be as illustrated in Figure R4508.4.
  7. Blocking shall be required at all joints if sheathing is used to resist uplift.
FIGURE R4508.4
PANEL ATTACHMENT TO COUNTER UPLIFT HORIZONTAL OR VERTICAL

TABLE R4508.4
UPLIFT CAPACITY OF WOOD STRUCTURAL PANEL SHEATHING USED TO RESIST BOTH LATERAL LOAD AND UPLIFTa
VERTICAL NAIL SPACING 8D @ 6" EDGE AND 12" INTERMEDIATE
Alternate nail spacing at top and bottom edges 6" 4" 3"
Uplift capacity (plf) nails – double row 240 474 710
For SI: 1 inch = 25.4 mm.
  1. Tabulated values are for Spruce-Pine-Fir framing. For Southern Pine framing the uplift values listed may be divided by 0.82.
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