Wall Covering
Exterior and interior wall coverings, siding, and weather barriers
Sections
Furring.
Where provided, furring shall consist of wood furring strips not less than 1 inch by 2 inches (25 mm by 51 mm), minimum 3/4-inch (19 mm) metal channels, or self-furring lath, and shall be installed in accordance with ASTM C1063.
Application.
The provisions of this chapter shall control the design and construction of the interior and exterior wall covering for buildings.
Installation.
INSIGHTS Products sensitive to adverse weather shall not be installed until adequate weather protection for the installation is provided. Exterior sheathing shall be dry before applying exterior cover.
General.
INSIGHTS Interior coverings or wall finishes shall be installed in accordance with this chapter and Tables R702.1(1), R702.1(2), R702.1(3) and R702.3.5.
Interior plaster.
INSIGHTS INSIGHTS (1)
Gypsum plaster.
Gypsum plaster materials shall conform to ASTM C5, C22, C28, C35, C59, C61, C587, C631, C847, C933, C1032 and C1047, and shall be installed or applied in compliance with ASTM C841, C842 and C843.
Cement plaster.
Cement plaster materials shall conform to ASTM C91 (Type M, S or N), C150 (Types I, II and III), C595 [Types IP, I (PM), IS and I (SM)], C847, C897, C933, C1032, C1047 and C1328, and shall be installed or applied in compliance with ASTM C926 and C1063. Gypsum lath shall conform to ASTM C1396.
Application.
Each coat shall be kept in a moist condition for not less than 24 hours prior to application of the next coat. Exception: Applications installed in accordance with ASTM C926.
Curing.
The finish coat for two-coat cement plaster shall not be applied sooner than 48 hours after application of the first coat. For three-coat cement plaster, the second coat shall not be applied sooner than 24 hours after application of the first coat.
Support.
Support spacing for gypsum or metal lath on walls or ceilings shall not exceed 16 inches (406 mm) for 3/8-inch-thick (9.5 mm) or 24 inches (610 mm) for 1/2-inch-thick (12.7 mm) plain gypsum lath.
Gypsum board and gypsum panel products.
ES
Materials.
Gypsum board and gypsum panel product materials and accessories shall conform to ASTM C22, C475, C514, C1002, C1047, C1177, C1178, C1278, C1396, C1658 or C1766 and shall be installed in accordance with the provisions of this section.
Adhesives.
Expandable foam adhesives for the installation of gypsum board and gypsum panel products shall conform to ASTM D6464. Other adhesives for the installation of gypsum board and gypsum panel products shall conform to ASTM C557.
Wood framing.
Wood framing supporting gypsum board and gypsum panel products shall be not less than 2 inches (51 mm) nominal thickness in the least dimension except that wood furring strips not less than 1-inch by 2-inch (25 mm by 51 mm) nominal dimension shall be permitted to be used over solid backing or framin...
Cold-formed steel framing.
Cold-formed steel framing supporting gypsum board and gypsum panel products shall be not less than 11/4 inches (32 mm) wide in the least dimension. Nonload-bearing cold-formed steel framing shall comply with AISI S220.
Insulating concrete form walls.
Foam plastics for insulating concrete form walls constructed in accordance with Sections R404.1.2 and R608 on the interior of habitable spaces shall be protected in accordance with Section R316.4. Use of adhesives in conjunction with mechanical fasteners is permitted.
Application.
INSIGHTS 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).
Screw fastening.
Screws for attaching gypsum board and gypsum panel products to wood framing shall be Type W or Type S in accordance with ASTM C1002 and shall penetrate the wood not less than 5/8 inch (15.9 mm). Gypsum board and gypsum panel products shall be attached to cold-formed steel framing with minimum No.
Horizontal gypsum board diaphragm ceilings.
INSIGHTS Gypsum board and gypsum panel products shall be permitted on wood joists to create a horizontal diaphragm in accordance with Table R702.3.6. Gypsum board and gypsum panel products shall be installed perpendicular to ceiling framing members.
Water-resistant gypsum backing board.
Gypsum 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.
Limitations.
Water-resistant gypsum backing board shall not be used where there will be direct exposure to water, or in areas subject to continuous high humidity.
General.
Ceramic tile surfaces shall be installed in accordance with ANSI A108.1, A108.4, A108.5, A108.6, A108.11, A118.1, A118.3, A136.1 and A137.1.
Backer boards.
Materials used as backers 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 installed in accordance with the manufacturer’s recommendations.
Other finishes.
Wood veneer paneling and hardboard paneling shall be placed on wood or cold-formed steel framing spaced not more than 16 inches (406 mm) on center.
Wood shakes and shingles.
Wood shakes and shingles shall conform to CSSB Grading Rules for Wood Shakes and Shingles and shall be permitted to be installed directly to the studs with maximum 24 inches (610 mm) on-center spacing.
Attachment.
Nails, staples or glue are permitted for attaching shakes or shingles to the wall, and attachment of the shakes or shingles directly to the surface shall be permitted provided the fasteners are appropriate for the type of wall surface material.
Furring strips.
Where furring strips are used, they shall be 1 inch by 2 inches or 1 inch by 3 inches (25 mm by 51 mm or 25 mm by 76 mm), spaced a distance on center equal to the desired exposure, and shall be attached to the wall by nailing through other wall material into the studs.
Vapor retarders.
ES INSIGHTS Vapor retarder materials shall be classified in accordance with Table R702.7(1). A vapor retarder shall be provided on the interior side of frame walls of the class indicated in Table R702.7(2), including compliance with Table R702.7(3) or R702.7(4) where applicable.
Spray foam plastic insulation for moisture control with Class II and III vapor retarders.
INSIGHTS For purposes of compliance with Tables R702.7(3) and R702.7(4), spray foam with a maximum permeance of 1.5 perms at the installed thickness applied to the interior side of wood structural panels, fiberboard, insulating sheathing or gypsum shall be deemed to meet the continuous insulation mo...
Exterior Covering
Parent section for all exterior wall covering (siding) requirements.
General (Exterior Covering)
Exterior walls must provide weather-resistant envelope with water-resistive barrier behind veneer and proper flashing.
Panel siding.
Fiber-cement panels shall comply with the requirements of ASTM C1186, Type A, minimum Grade II or ISO 8336, Category A, minimum Class 2. Panels shall be installed with the long dimension either parallel or perpendicular to framing.
Lap siding.
Fiber-cement lap siding having a maximum width of 12 inches (305 mm) shall comply with the requirements of ASTM C1186, Type A, minimum Grade II or ISO 8336, Category A, minimum Class 2.
Weather Resistance
Section R703.1.1 — Weather Resistance. Exterior walls shall provide the building with a weather-resistant exterior wall envelope. The 2024 IRC requires all exterior wall envelopes to include a water-resistive barrier, a...
Fiber Cement Siding
Fiber cement siding requirements — ASTM C1186 compliance, 5/16" minimum, 1-1/4" lap, WRB required.
Installation.
Vinyl siding, soffit and accessories shall be installed in accordance with the manufacturer’s instructions.
Fasteners.
Unless specified otherwise by the manufacturer’s instructions, fasteners for vinyl siding shall be 0.120-inch (3 mm) shank diameter nail with a 0.313-inch (8 mm) head or 16-gage staple with a 3/8-inch (9.5 mm) to 1/2-inch (12.7 mm) crown.
Penetration depth.
Unless specified otherwise by the manufacturer’s instructions, fasteners shall penetrate into building framing. The total penetration into sheathing, furring framing or other nailable substrate shall be a minimum 11/4 inches (32 mm).
Spacing.
Unless specified otherwise by the manufacturer’s instructions, the maximum spacing between fasteners for horizontal siding shall be 16 inches (406 mm), and for vertical siding 12 inches (305 mm) both horizontally and vertically.
Installation over foam plastic sheathing.
INSIGHTS Where vinyl siding or insulated vinyl siding is installed over foam plastic sheathing, the vinyl siding shall comply with Section R703.11 and shall have a wind load design pressure rating in accordance with Table R703.11.2. Exceptions: 1.
Wind resistance.
Wall coverings, backing materials and their attachments shall be capable of resisting wind loads in accordance with Tables R301.2.1(1) and R301.2.1(2). Wind-pressure resistance of the siding, soffit and backing materials shall be determined by ASTM E330 or other applicable standard test methods.
Adhered masonry veneer installation.
ES Adhered masonry veneer shall comply with the requirements of Section R703.7.3 and the requirements in Sections 12.1 and 12.3 of TMS 402. Adhered masonry veneer shall be installed in accordance with Section R703.7.1, Article 3.3C of TMS 602 or the manufacturer’s instructions.
Clearances.
On exterior stud walls, adhered masonry veneer shall be installed: 1. Minimum of 4 inches (102 mm) above the earth; 2.
Flashing at foundation.
A corrosion-resistant screed or flashing of a minimum 0.019-inch (0.48 mm) or 26-gage galvanized or plastic with a minimum vertical attachment flange of 31/2 inches (89 mm) shall be installed to extend a minimum of 1 inch (25 mm) below the foundation plate line on exterior stud walls in accordance w...
Water-resistive barrier.
A water-resistive barrier shall be installed as required by Section R703.2 and shall comply with the requirements of Section R703.7.3. The water-resistive barrier shall lap over the exterior of the attachment flange of the screed or flashing provided in accordance with Section R703.12.2.
Insulated vinyl siding.
Insulated vinyl siding shall be certified and labeled as conforming to the requirements of ASTM D7793 by an approved quality control agency.
Insulated vinyl siding and accessories.
Insulated vinyl siding and accessories shall be installed in accordance with the manufacturer’s installation instructions.
Polypropylene siding.
Polypropylene siding shall be certified and labeled as conforming to the requirements of ASTM D7254, and those of Section R703.14.2 or Section R703.14.3, by an approved quality control agency.
Polypropylene siding and accessories.
Polypropylene siding and accessories shall be installed in accordance with manufacturer’s installation instructions.
Installation.
Polypropylene siding shall be installed over and attached to wood structural panel sheathing with minimum thickness of 7/16 inch (11.1 mm), or other substrate, composed of wood or wood-based material and fasteners having equivalent withdrawal resistance.
Fastener requirements.
Unless otherwise specified in the approved manufacturer’s instructions, nails shall be corrosion resistant, with a minimum 0.120-inch (3 mm) shank and minimum 0.313-inch (8 mm) head diameter.
Fire separation.
Polypropylene siding shall not be installed on walls with a fire separation distance of less than 5 feet (1524 mm) and walls closer than 10 feet (3048 mm) to a building on another lot. Exception: Walls perpendicular to the line used to determine the fire separation distance.
Flame spread index.
The certification of the flame spread index shall be accompanied by a test report stating that all portions of the test specimen ahead of the flame front remained in position during the test in accordance with ASTM E84 or UL 723.
Vinyl Siding
Vinyl siding — ASTM D3679 compliance, WRB required, minimum fastener penetration of 1-1/4" into studs.
Direct attachment.
INSIGHTS Where cladding is installed directly over foam sheathing without the use of furring, cladding minimum fastening requirements to support the cladding weight shall be as specified in Table R703.15.1.
Furred cladding attachment.
INSIGHTS Where wood furring is used to attach cladding over foam sheathing, furring minimum fastening requirements to support the cladding weight shall be as specified in Table R703.15.2.
Cladding attachment over foam sheathing to cold-formed steel framing.
Cladding shall be specified and installed in accordance with Section R703, the cladding manufacturer’s approved instructions, including any limitations for use over foam plastic sheathing, or an approved design.
Direct attachment.
INSIGHTS Where cladding is installed directly over foam sheathing without the use of furring, cladding minimum fastening requirements to support the cladding weight shall be as specified in Table R703.16.1.
Furred cladding attachment.
INSIGHTS Where steel or wood furring is used to attach cladding over foam sheathing, furring minimum fastening requirements to support the cladding weight shall be as specified in Table R703.16.2.
Cladding attachment over foam sheathing to masonry or concrete wall construction.
Cladding shall be specified and installed in accordance with Section 703.3 and the cladding manufacturer’s instructions or an approved design.
Water-Resistive Barrier (WRB)
Water-resistive barrier (house wrap) required behind all exterior wall coverings, extending to top of wall with proper terminations.
Water-Resistive Barrier
Section R703.3 — Water-Resistive Barrier. One layer of No. 15 asphalt felt complying with ASTM D226, or other approved water-resistive barrier, shall be applied over studs or sheathing of all exterior walls. The water-resi...
Soffit installation.
INSIGHTS Soffits shall comply with Section R704. INSIGHTS (2) ➡
Wind limitations.
INSIGHTS Where the design wind pressure exceeds 30 psf or where the limits of Table R703.3.2 are exceeded, the attachment of wall coverings and soffits shall be designed to resist the component and cladding loads specified in Table R301.2.1(1) for walls, adjusted for height and exposure in accordanc...
Fasteners.
Exterior wall coverings and roof overhang soffits shall be securely fastened with aluminum, galvanized, stainless steel or rust-preventative coated nails or staples in accordance with Table R703.3(1) or with other approved corrosion-resistant fasteners in accordance with the wall covering manufactur...
Minimum fastener length and penetration.
Fasteners shall have the greater of the minimum length specified in Table R703.3(1) or as required to provide a minimum penetration into framing as follows: 1.
Flashing
Flashing required at all exterior wall penetrations, openings, intersections, and projections to prevent water entry.
Flashing at Wall Openings
Section R703.4.1 — Flashing at Wall Openings. Approved corrosion-resistant flashing shall be provided at the top and sides of all exterior window and door openings. Pan flashing shall be installed at the sill of all exterior w...
Wood Siding
Wood siding installation requirements including lap dimensions and WRB requirement.
Vertical wood siding.
Wood siding applied vertically shall be nailed to horizontal nailing strips or blocking set not more than 24 inches (610 mm) on center.
Panel siding.
Three-eighths-inch (9.5 mm) wood structural panel siding shall not be applied directly to studs spaced more than 16 inches (406 mm) on center where long dimension is parallel to studs.
Horizontal wood siding.
Horizontal lap siding shall be installed in accordance with the manufacturer’s recommendations.
Wood Structural Panel Siding
Wood structural panel siding installation — face grain perpendicular to studs, edges over framing, sealed joints.
Application.
Wood shakes or shingles shall be applied either single course or double course over nominal 1/2-inch (12.7 mm) wood-based sheathing or to furring strips over 1/2-inch (12.7 mm) nominal nonwood sheathing.
Weather exposure.
The maximum weather exposure for shakes and shingles shall not exceed that specified in Table R703.6.1.
Attachment.
INSIGHTS Wood shakes or shingles shall be installed according to this chapter and the manufacturer’s instructions.
Bottom courses.
The bottom courses shall be doubled.
Stone and Masonry Veneer
Section R703.7 — Stone and Masonry Veneer. Anchored masonry veneer shall not exceed 5 inches in nominal thickness. Veneer shall be anchored to the supporting wall with corrosion-resistant metal ties. Ties shall be spaced no...
Lath.
INSIGHTS Lath and lath attachments shall be of corrosion-resistant materials in accordance with ASTM C1063. Expanded metal, welded wire, or woven wire lath shall be attached to wood framing members or furring.
Plaster.
Plastering with cement plaster shall be in accordance with ASTM C926. Cement materials shall be in accordance with one of the following: 1.
Weep screeds.
A minimum 0.019-inch (0.5 mm) (No. 26 galvanized sheet gage), corrosion-resistant weep screed or plastic weep screed, with a minimum vertical attachment flange of 31/2 inches (89 mm), shall be provided at or below the foundation plate line on exterior stud walls in accordance with ASTM C926.
Water-resistive barriers.
INSIGHTS Water-resistive barriers shall be installed as required in Section R703.2 and, where applied over wood-based sheathing, shall comply with Section R703.7.3.1 or R703.7.3.2. ➡ INSIGHTS (3)
Dry climates.
INSIGHTS In Dry (B) climate zones indicated in Figure N1101.7, water-resistive barriers shall comply with one of the following: 1.
Moist or marine climates.
INSIGHTS In the Moist (A) or Marine (C) climate zones indicated in Figure N1101.7, water-resistive barriers shall comply with one of the following: 1.
Application.
Each coat shall be kept in a moist condition for at least 48 hours prior to application of the next coat. Exception: Applications installed in accordance with ASTM C926.
Curing.
The finish coat for two-coat cement plaster shall not be applied sooner than seven days after application of the first coat. For three-coat cement plaster, the second coat shall not be applied sooner than 48 hours after application of the first coat.
Flashing at Exterior Wall Intersections
Kick-out flashing and exterior wall intersection flashing requirements.
Interior veneer support.
Veneers used as interior wall finishes shall be permitted to be supported on wood or cold-formed steel floors that are designed to support the loads imposed.
Exterior veneer support.
Except in Seismic Design Categories D0, D1 and D2, exterior masonry veneers having an installed weight of 40 pounds per square foot (195 kg/m2) or less shall be permitted to be supported on wood or cold-formed steel construction.
Support by steel angle.
A minimum 6-inch by 4-inch by 5/16-inch (152 mm by 102 mm by 8 mm) steel angle, with the long leg placed vertically, shall be anchored to double 2-inch by 4-inch (51 mm by 102 mm) wood studs or double 350S162 cold-formed steel studs at a maximum on-center spacing of 16 inches (406 mm).
Support by roof construction.
A steel angle shall be placed directly on top of the roof construction.
Lintels.
Masonry veneer shall not support any vertical load other than the dead load of the veneer above. Veneer above openings shall be supported on lintels of noncombustible materials.
Allowable span.
The allowable span shall not exceed the values set forth in Table R703.8.3.1. TABLE R703.8.3.1 ALLOWABLE SPANS FOR LINTELS SUPPORTING MASONRY VENEERa, b, c, d SIZE OF STEEL ANGLEa, c, d (inches) NO STORY ABOVE ONE STORY ABOVE TWO STORIES ABOVE NO.
Maximum span.
The allowable span shall not exceed 18 feet 3 inches (5562 mm) and shall be constructed to comply with Figure R703.8.3.2 and the following: 1. Provide a minimum length of 18 inches (457 mm) of masonry veneer on each side of opening as shown in Figure R703.8.3.2.
Anchorage.
INSIGHTS Masonry veneer shall be anchored to the supporting wall studs with corrosion-resistant metal ties embedded in mortar or grout and extending into the veneer a minimum of 11/2 inches (38 mm), with not less than 5/8-inch (15.9 mm) mortar or grout cover to outside face.
Size and spacing.
INSIGHTS Veneer ties, if strand wire, shall be not less in thickness than No. 9 U.S.
Veneer ties around wall openings.
Additional metal ties shall be provided around wall openings greater than 16 inches (406 mm) in either dimension. Metal ties around the perimeter of openings shall be spaced not more than 3 feet (9144 mm) on center and placed within 12 inches (305 mm) of the wall opening.
Grout fill.
As an alternative to the airspace required by Table R703.8.4(1), grout shall be permitted to fill the airspace. Where the airspace is filled with grout, a water-resistive barrier is required over studs or sheathing.
Flashing.
Flashing shall be located beneath the first course of masonry above finished ground level above the foundation wall or slab and at other points of support, including structural floors, shelf angles and lintels where masonry veneers are designed in accordance with Section R703.8.
Weepholes.
Weepholes shall be provided in the outside wythe of masonry walls at a maximum spacing of 33 inches (838 mm) on center. Weepholes shall be not less than 3/16 inch (5 mm) in diameter.
Exterior insulation and finish system (EIFS)/EIFS with drainage.
ES Exterior insulation and finish systems (EIFS) shall comply with this chapter and Section R703.9.1. EIFS with drainage shall comply with this chapter and Section R703.9.2.
Exterior insulation and finish systems (EIFS).
EIFS shall comply with the following: 1. ASTM E2568.
Exterior insulation and finish system (EIFS) with drainage.
EIFS with drainage shall comply with the following: 1. ASTM E2568.
General wind limitations.
Where the design wind pressure is 30 pounds per square foot (1.44 kPa) or less, soffits shall comply with Section R704.2. Where the design wind pressure exceeds 30 pounds per square foot (1.44 kPa), soffits shall comply with Section R704.3.
Soffit installation where the design wind pressure is 30 psf or less.
Where the design wind pressure is 30 pounds per square foot (1.44 kPa) or less, soffit installation shall comply with Section R704.2.1, R704.2.2, R704.2.3 or R704.2.4.
Vinyl soffit panels.
Vinyl soffit panels shall be installed using fasteners specified by the manufacturer and shall be fastened at both ends to a supporting component such as a nailing strip, fascia or subfascia component in accordance with Figure R704.2.1(1).
Fiber-cement soffit panels.
Fiber-cement soffit panels shall be a minimum of 1/4 inch (6.4 mm) in thickness and shall comply with the requirements of ASTM C1186, Type A, minimum Grade II, or ISO 8336, Category A, minimum Class 2. Panel joints shall occur over framing or over wood structural panel sheathing.
Hardboard soffit panels.
Hardboard soffit panels shall be not less than 7/16 inch (11.11 mm) in thickness and shall be fastened to framing or nailing strips with 21/2-inch by 0.113-inch (64 mm by 2.9 mm) siding nails spaced not more than 6 inches (152 mm) on center at panel edges and 12 inches (305 mm) on center at intermed...
Wood structural panel soffit.
INSIGHTS The minimum nominal thickness for wood structural panel soffits shall be 3/8 inch (9.5 mm) and shall be fastened to framing or nailing strips with 2-inch by 0.099-inch (51 mm by 2.5 mm) nails.
Soffit installation where the design wind pressure exceeds 30 psf.
Where the design wind pressure is greater than 30 psf, soffit installation shall comply with Section R704.3.1, R704.3.2, R704.3.3 or R704.3.4. Soffit materials not addressed in Sections R704.3.1 through R704.3.4 shall be in accordance with the manufacturer’s installation instructions.
Vinyl soffit panels.
Vinyl soffit panels and their attachments shall be capable of resisting wind loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.929 m2) and adjusted for height and exposure in accordance with Table R301.2.1(2) .
Fiber-cement soffit panels.
Fiber-cement soffit panels shall comply with Section R704.2.2 and shall be capable of resisting wind loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.929 m2) and adjusted for height and exposure in accordance with Table R301.2.1(2).
Hardboard soffit panels.
Hardboard soffit panels shall comply with the manufacturer’s installation instructions and shall be capable of resisting wind loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.929 m2) and adjusted for height and exposure in accordance with Table R301.2....
Wood structural panel soffit.
Wood structural panel soffit. Wood structural panel soffits shall be capable of resisting wind loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.929 m2) and adjusted for height and exposure in accordance with Table R301.2.1(2).