Roof-Ceiling Construction

Roof Drainage

ROOF DRAINAGE - Must prevent water accumulation. Gutters/downspouts sized per ASPE/SMACNA.

Identification

Dimension lumber for ceiling joists, rafters, and roof framing must be identified by a grade mark from an approved lumber grading agency. Required for structural integrity verification during roof replacement or repair.

Wood Trusses

Wood trusses must be designed by a registered design professional. Requires truss design drawings on site during inspection. Alterations to trusses, including cutting or field modifications, are not permitted without approval of a registered design professional.

Roof Tie-Down

Roof assemblies subject to wind uplift must have a continuous load path from the roof to the foundation. Connections must resist design uplift forces. Applies to rafter-to-wall and truss-to-wall connections. Hurricane clips/straps are a common solution.

Hurricane Straps and Roof-to-Wall Connections

Hawaii REQUIRES hurricane straps/clips at ALL roof-to-wall connections (statewide mandate). Use engineered connectors (Simpson H2.5 typical, H10A for high uplift) rated for design wind speed. Proper fastening per manufacturer (10d/16d nails, full count). Inspection required before covering. Corrosion-resistant in coastal areas. Continuous load path from roof to foundation with no gaps.

Hurricane Straps and Roof-to-Wall Connections (Gulf Coast MANDATORY)

Mississippi Gulf Coast REQUIRES hurricane straps at ALL roof-to-wall connections (post-Katrina). Use engineered connectors (Simpson H10A typical for coastal, H16 for extreme wind). Follow manufacturer fastening exactly. Inspection required before covering. Corrosion-resistant on coast. Continuous load path from roof to foundation mandatory. Wind speeds 150-180 mph demand robust connections.

Design and Construction — Ceiling Joists

Ceiling joists must be continuous or spliced over bearing points. Minimum bearing length 1-1/2 inches on wood/metal and 3 inches on masonry/concrete. Lateral support at bearing points and at 8 ft intervals maximum.

Rafters

Covers span tables, bearing requirements, and framing details for rafters. Ridge board, collar ties, and rafter ties requirements. Notch and boring limitations specified.

Rafter Spans

Provides allowable rafter spans for common lumber species and grades based on rafter spacing, dead load, live load (20 psf ground snow load), and roof slope.

Roof Sheathing

Parent section for all roof sheathing requirements including lumber sheathing and wood structural panels.

Lumber Sheathing

Allowable spans for lumber used as roof sheathing. Spaced lumber sheathing for wood shingle and shake roofing shall conform to Sections R905.7 and R905.8 requirements.

Wood Structural Panel Sheathing

Wood structural panel roof sheathing shall be per Table R503.2.1.1(1) or engineered per APA. Panel orientation, nailing schedule, and edge support requirements. Critical for reroof scopes — if sheathing is damaged, replacement must meet current code.

Roof Sheathing Fastening

Nail type, size, and spacing for attaching roof sheathing. 8d common or 6d deformed nails at 6 inches on center at edges and 12 inches on center in field (standard). Enhanced nailing schedules apply in high-wind zones.

Allowable Spans

MINIMUM ROOF SHEATHING THICKNESS - Specifies minimum thickness based on rafter/truss spacing.

Installation

Installation requirements for wood structural panel roof sheathing. Max 9" cantilever at gable ends.

Roof Ventilation

Attic ventilation required. 1/150 ratio standard; may be reduced to 1/300 with vapor retarder and balanced ventilation.

Ventilation Required

ATTIC VENTILATION: Minimum 1/150 ratio (reduces to 1/300 with balanced vents or vapor retarder). MUST maintain 1" clearance at eaves for airflow. Use baffles to keep insulation from blocking soffit vents. 50/50 split between intake (soffit) and exhaust (ridge) is ideal. Do NOT mix power vents with ridge vents.

Minimum Vent Area

MINIMUM VENT AREA - 1/150 ratio required, or 1/300 with 40-50% upper ventilation.

Attic Ventilation - Hawaii Moisture and Heat Management

Hawaii attic ventilation critical for moisture and heat management in Very Hot-Humid climate. Minimum 1:150 ratio (net free area to floor area), or 1:300 with vapor retarder and balanced ventilation. Ridge vents + soffit vents preferred. All vents must be wind-rated (105-130 mph). Insulation baffles required at soffits. Exhaust fans vented to exterior, NOT attic. Unvented attic allowed with spray foam at roof deck.

Attic Ventilation - Indiana Ice Dam Prevention

Indiana attic ventilation critical for ice dam prevention (entire state in zones 4A/5A). Minimum 1:150 ratio (or 1:300 with vapor retarder + balanced ventilation). Ridge vents + soffit vents preferred. Insulation baffles REQUIRED at soffits. Vapor retarder on warm side (ceiling). Bath/kitchen exhaust to exterior, NOT attic. Northwest IN (lake effect) particularly susceptible to ice dams.