1/2-inch through-bolts or 5/16- to 3/8-inch structural screws are the standard for built-up wood headers in residential framing; use corrosion-resistant hardware and follow the engineer’s or plan’s specifications.
Headers span openings such as doors and windows and must transfer loads safely to the surrounding studs. The best bolt choice depends on header type (built-up lumber, LVL or engineered wood, or steel), the opening span, climate, and local code requirements. This article explains common bolt options, typical sizes, placement guidelines, and installation practices to help builders and DIYers install headers that meet safety standards.
Understanding headers in wood framing
In typical wood-frame construction, headers are built-up members (often two or more pieces of 2x lumber or an engineered LVL) placed over openings to bear loads from above and distribute them to the jack and king studs. Proper fastening along the length of the header is essential to resist shear, rotation, and uplift, especially on exterior walls or large openings.
Bolt options for headers
Below are the bolt categories most commonly used to secure headers. Each is followed by a list of practical details and considerations.
Through-bolts
- Use 1/2-inch diameter through-bolts (galvanized or stainless) to pass entirely through the header and both adjacent studs. Provide washers on both ends and nuts tightened securely.
- Typical practice places bolts near each end of the header and, for longer spans, one in the middle. Length should extend well beyond the far side into the stud formation to ensure a strong bite.
- Pros: Very strong, spreads load across multiple members; good for long spans or heavy loads.
- Cons: Requires accurate drilling through all members; can be more labor-intensive.
For many residential openings, through-bolts offer a robust, code-friendly option, especially when combined with proper nailing and built-up header construction.
Structural screws
- Use large-diameter structural screws in the range of 5/16" to 3/8" diameter, typically 3" to 4" long to pass through the header and into the studs.
- Common options include approved structural screws from brands such as GRK, SPAX, or Simpson Strong-Tie. Use corrosion-resistant coatings for exterior exposure.
- Pros: Faster installation than through-bolts; often easier to retrofit; strong shear performance when installed per manufacturer's guidelines.
- Cons: In some applications, fewer screws may be allowed than through-bolts; you must follow the engineer’s or plan’s specifications.
Structural screws are a popular alternative to through-bolts when the installation needs to be quicker or where drilling through all members is impractical, provided they meet design loads.
Carriage bolts and lag screws
- Carriage bolts (1/2" diameter) with nuts and washers or heavy-duty lag screws (5/16"–3/8" diameter) are commonly used in certain retrofit or timber-framed applications.
- Lengths typically range from 3" to 6" depending on member thickness and required embedment.
- Pros: Simple to install and widely available; good for penetrating into solid studs or blocking.
- Cons: May require more precise alignment; lag screws can loosen over time if not properly tightened or if vibration is present.
Carriage bolts and lag screws provide flexible options in retrofit scenarios or when coordinating with existing framing details, but should be used with confirmation from plans or an engineer.
Special cases: engineered headers and steel headers
Engineered headers (LVLs or glulam) and steel lintels follow manufacturer or design-spec guidelines. For LVLs and similar products, fastener requirements are typically specified in the engineered drawings and can include through-bolts or structural screws that meet the load ratings. For steel lintels, anchorages and bolts are often dictated by the lintel manufacturer and the masonry conditions; use the specified size, type, and spacing and ensure compatibility with edge distances and weather exposure. When in doubt, defer to the design details provided by a structural engineer or the hardware manufacturer.
Sizing, spacing, and installation tips
Before listing practical practices, consider how bolt size, placement, and installation affect the header’s performance and the wall assembly.
- Through-bolts: typically 1/2" diameter; place near each end of the header and, for longer spans, one in the middle; use washers and nuts; ensure the bolts pass through the header and into the stud bays to maximize load transfer.
- Structural screws: typically 5/16"–3/8" diameter; 3"–4" long; space similarly to through-bolts (ends and middle as required by span); follow manufacturer torque guidelines.
- Edge distances and predrilling: predrill pilot holes to prevent splitting; maintain adequate edge distance from the stud face (the exact distance depends on member size and fastener type).
- Corrosion considerations: use galvanized or stainless hardware for exterior walls or high-humidity environments to prevent rust and ensure long-term performance.
- Compliance: always align with local building codes (IRC/IBC) and the header design in the construction documents; for large openings or unusual loads, rely on engineered details.
Adhering to proper sizing and spacing helps ensure the header retains its load-carrying capacity and that the wall assembly remains durable over time.
Installation tips and best practices
These practical steps help translate the bolt choices into a safe, code-compliant installation.
- Predrill holes to avoid splitting the header and studs; ensure holes are centered on the member where possible.
- Keep bolts plumb and aligned with the studs to prevent twisting or uneven load transfer.
- Use washers to distribute load and prevent bearing damage on the header and stud faces.
- In exterior walls, choose corrosion-resistant hardware and seal penetrations to protect against water intrusion.
- Do not rely on nails alone for header connections when designed loads require bolts or manufacturer-approved connectors; use the specified combination of fasteners as required.
Following these practices reduces the risk of header movement, sag, or joint failure over time.
Code considerations and professional guidance
Header installation is a structural matter. Always consult local building codes and project plans. In many jurisdictions, the IRC/IBC and local amendments specify minimum fastener types, sizes, and spacing for headers, and engineered plans may require specific connectors or reinforcement. For unusually large openings, high-load conditions, or retrofit work, engaging a licensed structural engineer or a qualified contractor ensures the details meet current standards.
Summary
The right bolts for headers depend on header type, span, and environment. In most residential framing, 1/2-inch through-bolts or 5/16- to 3/8-inch structural screws secured with washers and installed per engineered details provide reliable load transfer. Carriage bolts and lag screws offer alternatives in retrofit or specific applications, while engineered LVLs and steel lintels require manufacturer-approved fasteners. Always follow code requirements, use corrosion-resistant hardware for exterior work, and consult design documents or a structural professional for large or complex openings. Proper installation—predrilling, correct edge distances, and correct bolt placement—ensures a safe, durable header system.