Code Corner
by Robert Privott, NCHBA Director of Codes and Construction
Privott
North Carolina Building Code Council update
T
he North Carolina Building Code Council
will meet March 9-10, 2009, at the N.C.
Department of Insurance, 322 Chapanoke
Drive, Raleigh, NC 27603. The council will
hold a work session at 9 a.m., Monday, March 9,
followed by a public hearing at 1 p.m. The council
meeting will be at 9 a.m., Tuesday, March 10. The
agenda for the council meeting can be found at:
http://www.ncdoi.com/OSFM/Engineering/BCC/
engineering_bcc_agenda.asp.
Code changes to the 2009 North Carolina
Residential Code will continue to be the focus for
the next several issues of Code Corner.
North Carolina 2009
Residential Code changes
(continued from the January/February issue of North
Carolina Builder)
Highlights on changes between
the 2006 and 2009 North
Carolina Residential Code
SECTION 403 FOOTINGS
403.1.4 Minimum depth. All exterior
footings and foundation systems shall extend
below the frost line specified in Table R301.2(1).
In no case shall the bottom of the exterior footings
be less than 12 inches below the undisturbed ground
surface or engineered fill.
North Carolina change – Removed “be placed
at least 12 inches (305 mm) below the undisturbed
ground. Where applicable, the depth of footings
shall also conform to Sections R403.1.4.1 through
R403.1.4.2.”
FIGURE 403.1(1) (on facing page)
CONCRETE AND MASONRY
FOUNDATION DETAILS
North Carolina change - Removed the word
“finished” from Note 1. Now reads … Foundations
shall extend not less than 12 inches below the grade
or engineered fill and in no case less than the frost
line depth.
403.1.6 Foundation anchorage. When
braced wall panels are supported directly on
continuous foundations, the wall wood sill
plate or cold-formed steel bottom track shall be
anchored to the foundation in accordance with
this section.The wood sole plate at exterior walls
on monolithic slabs and wood sill plate shall be
anchored to the foundation with anchor bolts
spaced a maximum of 6 feet (1829 mm) on
center and not more than 12 inches from the
corner. There shall be a minimum of two bolts per
plate section…
North Carolina change – Added the sentence
requiring two bolts per plate section for wood sole
plates at exterior walls and wood sill plates.
TABLE R402.2 MINIMUM SPECIFIED COMPRESSIVE STRENGTH OF CONCRETE
MINIMUM SPECIFIED COMPRESSIVE STRENGTH
Weathering Potential b
CHAPTER 4 FOUNDATIONS
TYPE OR LOCATION OF CONCRETE CONSTRUCTION
Negligible
Moderate Severe
SECTION R401 GENERAL
Basement walls, foundations and other concrete
not exposed to the weather
2,500 2,500 2,500 c
Basement slabs and interior slabs on grade, except garage floor slabs
2,500 2,500 2,500 c
Basement walls, foundation walls, exterior walls and other vertical concrete work exposed
to the weather
2,500 3,000 3,000 d
Porches, carport slabs and steps exposed to the weather and garage floor slabs
2,500 3,000 d, e, f 3,500 d, e, f
R401.3 Drainage. The grade shall fall a
minimum of 6 inches within the first 10 feet.
Exception:Where lot lines, slopes or other physical
barriers prohibit 6 inches of fall within 10 feet, the
final grade shall slope away from the foundation a
minimum of 5 percent and the water shall be directed
toward drains or swales to ensure drainage away from
the structure….
IRC change - Added some new language dealing
with exception to the 6 inches in 10 feet positive
drainage slope of grade from building.This requires final
grade to have a 5 percent slope to a swale and a 2
percent slope to the swale if located within 10 feet of
a building.
TABLE R402.2 (at right)
MINIMUM SPECIFIED COMPRESSIVE
STRENGTH OF CONCRETE
IRC change - Add foot F dealing with garage slab
applications which is a (reduction of the total air content
(percent by volume of concrete) to not less than 3 percent
is permitted if the compressive strength of the concrete is
increased to not less than 4,000 psi.
6   North Carolina Builder
For SI: 1 pound per square inch = 6.895 kPa.
a. Strength at 28 days psi.
b. See Table R301.2(f) for weathering potential.
c. Concrete in these locations that may be subject to freezing and thawing during construction shall be
air-entrained concrete in accordance with Footnote d.
d. Concrete shall be air-entrained. Total air content (percent by volume of concrete) shall be not less
than 5 percent or more than 7 percent.
e. See Section R402.2 for maximum cementitious materials content.
f. For garage floors with a steel troweled finish, reduction of total air content (percent by volume of
concrete) to be not less than 3 percent is permitted if the specified compressive strength of the
concrete is increased to not less than 4,000 psi.
March 2009
TABLE 403.1(1) CONCRETE AND MASONRY FOUNDATION DETAILS
and species and for other loading conditions, refer
to the AF&PA Span Tables for Joists and Rafters.
IRC change - Added new standard “APA E30”
that can also be used instead of table R502.3.2.1(1)
for wood panels used as subflooring or combination
subfloor underlayment.
TABLES R502.3.1(1) and (2) FLOOR JOIST
SPANS FOR COMMON LUMBER SPECIES
a. & b.“Dead load limits for townhouses in
Seismic Design Category C and all structures
in Seismic Design Categories D0, D1, and D2
shall be determined in accordance with Section
R301.2.2.2.1.”
IRC change - Added footnotes (a & b) which
will apply to townhouses in seismic design category C
in North Carolina and limits dead loads per section
R301.2.2.2.1.
SECTION R404 FOUNDATION AND
RETAINING WALLS
R404.1
Concrete
and
masonry
foundation walls. Concrete and masonry
foundation walls shall be selected and constructed
in accordance with the provisions of Section
R404 or in accordance with ACI 318, ACI 332,
NCMA TR68–A or ACI 530/ASCE 5/TMS
402 or other approved structural standards.
Foundation walls that meet all of the following shall
be considered laterally supported:
1. Full basement floor shall be 3.5 inches (89 mm)
thick concrete slab poured tight against the bottom of the
foundation wall.
2. Bolt spacing for the sill plate shall be no greater
than per Table R404.1(2). 3’-0”.
3.Where foundation walls support unbalanced load
on opposite sides of the building, such as a daylight
basement, the building aspect ratio, L/W, shall not
exceed the value specified in Table R404.1(3). For such
foundation walls, the rim board shall be attached to the
sill with a 20-gauge metal angle clip at 24 inches (610
mm) on center, with five 8d nails per leg, or an approved
connector supplying 230 pounds per linear foot (3.36
kN/m) capacity.
North Carolina has adopted 2006 IRC 404.1
Section name has been changed to include “Retaining
Walls”. Notes have been added reference foundation
walls being considered laterally supported.
TABLE R404.1(1) TOP REACTIONS
AND PRESCRIPTIVE SUPPORT FOR
FOUNDATION WALLS
Has been deleted in its entirety
TABLE R404.1 (2) MAXIMUM PLATE
ANCHOR-BOLT SPACING FOR
SUPPORTED FOUNDATION WALL
Has been deleted in its entirety
TABLES R404.1.1 (1); R404.1.1 (2); R404.1.1 (3);
R404.1.1 (4); R404.1.1 (5)
R404.1.1 (1) Plain masonry foundation walls
March 2009
R404.1.1 (2) 8-inch masonry walls with
Reinforcing;
R404.1.1 (3) 10-inch masonry walls with
reinforcing;
R404.1.1 (4) 12-inch masonry walls with
reinforcing
R404.1.1 (5) Concrete foundation walls
IRC change - Reworked tables by separating
information. Masonry and plain concrete are separate
tables now and added additional information to some
tables.
CHAPTER 5 - FLOORS
SECTION R502 WOOD FLOOR
FRAMING
R502.1.6 Structural log members.
Stress grading of struc­tural log members of
nonrectangular shape, as typically used in log
buildings, shall be in accordance with ASTM
D 3957. Such structural log members shall be
identified by the grade mark of an approved lumber
grading or inspection agency. In lieu of a grade
mark on the material, a certificate of inspection as
to species and grade issued by a lum­ber-grading
or inspection agency meeting the requirements
of this section shall be permitted to be accepted.
IRC change - This section has been added to
address a standard for log homes and requirement for
grade marks on materials.
R502.2.1 Framing at braced wall lines.
A load path for lateral forces shall be provided
between floor framing and braced wall panels
located above or below a floor, as specified in
Section R602.10.8.
IRC change - New requirement to include a load
path for lateral forces through any floor system from
braced wall line above or below as indicated in section
R602.10.8.
R502.3 Allowable joist spans. Spans for
floor joists shall be in accordance with Tables
R502.3.1(1) and R502.3.1(2). For other grades
TABLE R502.3.3 (1) CANTILEVER SPANS
FOR FLOOR JOISTS SUPPORTING LIGHTFRAME EXTERIOR BEARING WALL AND
ROOF ONLY
f. See Section R301.2.2.2.2, Item 1, for additional
limitations on cantilevered floor joists for detached oneand two-family dwellings in Seismic Design Category
D0, D1, or D2 and townhouses in Seismic Design
Category C, D0, D1, or D2.
IRC change - Added footnote (f) which will
apply to townhouses in seismic design category C
in North Carolina and limits dead loads per section
R301.2.2.2.1.
502.3 ALLOWABLE JOIST SPANS
R502.3.1 Sleeping areas and attic joists.
Table R502.3.1(1) shall be used to determine
the maximum allowable span of floor joists that
support sleeping areas and attics that are accessed
by means of a fixed stairway in accordance with
Section R311.5 provided that the design live load
does not exceed 30 psf (1.44 kPa) and the design
dead load does not exceed 20 psf (0.96 kPa).The
allowable span of ceiling joists that support attics
used for limited storage or no stor­age shall be
determined in accordance with Section R802.4.
IRC change - This section has added language that
identifies if an attic is accessible by a fixed set of stairs in
accordance with section R311.5 (stairway section) the
joists must be sized as floor joists not ceiling joists.
SECTION R506 CONCRETE FLOORS (ON
GROUND)
R506.2.4 Reinforcement support. Where
provided in slabs on ground, reinforcement shall
be supported to remain in place from the center
to upper one third of the slab for the duration of
the concrete placement.
IRC change - Added new code section that addresses
the requirement for all required steel to be supported in
place during concrete placement.
North Carolina Builder   7