A roof has many components: trusses or rafters, sheathing or decking, flashing, ridge, valley, eave, fascia, soffit, and underlayment. Today, we will study two components: roof sheathing and flashing.
The layer of boards or panels underneath your shingles or other roofing material is roof decking or sheathing. It serves as the foundation of your roofing system. Roof flashing is a weatherproofing material consisting of metal or rubber. It prevents water seepage at vulnerable points on a roof. Roofers place flashing on the roof sheathing at joints, angles, or seams. Some vital intersections include where the roof meets a wall, chimney, or skylight. Understanding the basics of roof construction helps homeowners make informed decisions when repairing or replacing their roofs.
The Role of Roof Sheathing
Flat material fastened to your roof rafters or trusses is roof sheathing or decking. It creates a solid surface for installing your roof covering. Sheathing serves several vital functions:
– Connects the rafters for added stability
– Provides a stable base on which to install shingles, metal roofing, or other roof coverings
– Contributes to the structural integrity and weather resistance of the roof
Proper installation of roof sheathing is critical for roof performance and leak prevention. That’s why using the right type and thickness of sheathing is so important.
The Two Main Types of Roof Sheathing
There are two basic categories of sheathing used on most residential roofs:
- Wood Planks
In the past, wood planks were traditionally used as roof sheathing. Roofers installed 1×6, 1×8, or 1×10 boards perpendicular to the rafters below. The gaps between each plank allowed for ventilation in the attic space.
Cedar planks, a common choice in past years, are naturally rot-resistant. Other popular wood species were pine and spruce. Though no longer common for new roofs, you may encounter wood plank sheathing if your home is older. A significant advantage of wood decking is that a roofer can repair it by replacing individual damaged planks.
2. Plywood and OSB (Oriented Strand Board) Sheathing
Plywood and OSB roof sheathing have largely replaced solid wood planks. Plywood sheets are 4×8-foot panels made from layers of wood veneers glued together. Wood chips are layered and adhered to produce sheets of OSB.
The advantage of panelized sheathing is a continuous, solid surface for shingles or other roofing materials. Staggered, covered seams between panels help with water resistance. Compared to wood planks, large sheets minimize gaps that can allow moisture intrusion and air leaks.
Plywood and OSB panels come in various thicknesses, such as 1/2 inch, 5/8 inch, and 3/4 inch. Thicker panels generally provide more rigidity and strength for the roof structure. Building codes specify minimum sheathing thickness for roofs. Different regions have different requirements, especially where there are snow load considerations.
Different Decking Types
Generally, you can expect to find these kinds of roof sheathing in homes of different eras:
Pre-1950s: Sawn wood planks were the most common roof sheathing used on older homes. Cedar, pine, and spruce were typical wood species utilized before the 1950’s.
1950s-1980s: The building industry transitioned to using plywood roof sheathing during this era. The convenient large panels became more widely available.
Post-1980s: OSB roof sheathing grew popular as an economical alternative to plywood. It dominates much of today’s construction.
Older homes that have had their roofs replaced may have modern sheathing.
Key Considerations About Your Roof Sheathing
When inspecting your roof, building a new home, or replacing your roof, a professional roofer will:
- Use the correct thickness of sheathing for proper structural support. They will determine this based on your roof span and local weather conditions.
- Look for sagging roof sections, indicating deteriorated or undersized decking. Compromised sheathing cannot support the weight of roofing materials,
- Inspect for water stains, dark areas, or soft spots that signify leaks and weakened sheathing.
- Allow 1/8 inch gap spacing between panels to allow for expansion and prevent buckling.
- Stagger panel joints across multiple rafters. They will also install seams over rafters to maintain a solid decking surface.
- Cover all seams for moisture protection.
- For improved structural integrity, replace damaged or deteriorated sections of sheathing.
The sheathing is the critical foundation for installing and supporting your shingles, tiles, or metal roof. Replacement of rotted roof decking is critical for receiving a manufacturer’s warranty from companies like Owens Corning, CertainTeed, or GAF.
The Role of Roof Flashing
Flashing is adhered to the roof sheathing to protect seams next to roof protrusions. Roof flashing directs water away from vulnerable seams on your roof, including:
- Next to vents, skylights, and chimneys
- Valley intersections
- Roof intersections with walls
Roof flashing prevents leaks by creating a watertight seal. Flashing protects a roof from water infiltration, ensuring its integrity and longevity.
Good quality components of a roof help prevent leaks and are critical for a long roof life. Ensure your roof sheathing and flashing remain in good shape by having a professional roofer inspect and repair your roof or re-roof your home. It will pay off in the long run.
To consult with a trusted roofer about components of your roof or if you need recommendations for a roof replacement, contact O’LYN Roofing today!
