If you’ve ever walked through a post-and-beam barn, a modern cross-laminated timber (CLT) office building, or even a custom backyard pavilion with exposed heavy timbers, you’ve probably spotted them: those robust, silver or galvanized fasteners holding the whole structure together. For years, the construction industry wrote off structural bolts as only for steel or concrete, the workhorses of commercial and industrial builds that wood, to many, was too soft, too prone to shifting, or too susceptible to rot to pair with such heavy-duty hardware. But as a structural bolts supplier that’s worked with both residential carpenters and large commercial architects over the past 12 years, I can tell you this: structural bolts aren’t just for steel anymore—and using them in wooden structures isn’t just possible, it’s often the smarter, safer choice for long-lasting, code-compliant builds. Structural Bolts
I didn’t always think this way. Early in my career, I sold mostly to steel fabricators and bridge contractors, and wood structures felt like a separate lane, one I didn’t need to worry about. That changed in 2015, when a small custom timber frame builder from Vermont knocked on our warehouse door, panicking. He’d bid on a project for a 3,000-square-foot post-and-beam home that required attaching 12×12 glulam columns to a concrete foundation, and the standard lag screws he’d used for years kept pulling out during load tests. “The wood’s too dense in spots, too soft in others,” he told me, slamming a sample lag screw that had snapped halfway into a timber beam. “I need something that can hold, something that doesn’t risk splitting the timber when I tighten it.”
That’s when I started digging. I pulled our old engineering resources, poured over 2015 International Building Code (IBC) updates, and even sat in on a forest products engineering seminar at a nearby university to get answers. What I learned changed everything: structural bolts, when specified correctly, meet (and often exceed) the load requirements for wood connections, and they address many of the pain points that have long tripped up wood builders.
First, let’s clarify what we mean by “structural bolts” here. These aren’t the tiny bolts you use for a shelf or a backyard play set. We’re talking about heavy-duty fasteners—usually hot-dip galvanized, stainless steel, or weatherproof coated—that have consistent tensile strength (the amount of pull force they can handle) and shear strength (the amount of side force they can resist) rated by engineering standards like ASTM A325, ASTM A490, or ISO 898. For wood, these properties are non-negotiable: a connection that holds a 20-foot glulam beam to a post during a snow load or seismic shift can’t fail, period.
The biggest myth I hear from builders is that wood is too brittle to handle structural bolts, that driving or tightening a large bolt will split the timber. That’s only true if you skip two critical steps: calculating the correct hole size and using pre-drilled pilot holes. For softwoods like pine or spruce, the pilot hole should be 80-90% of the bolt’s shank diameter; for dense hardwoods or glulam timbers (which are engineered to be stronger than solid wood), you can go a touch tighter, around 90-95%. Back in that 2015 Vermont project, we suggested 1-inch diameter A325 bolts with 15/16-inch pilot holes, spaced 4 inches apart along the joint, instead of the 2-inch spacing he’d used for lag screws. The load test came back 22% over the required minimum, and that home still stands today—we still get holiday cards from the builder with photos of the exposed bolted joints, no splits, no issues.
Another myth: wood connections need specialized fasteners like self-tapping screws or timber rivets to be structural. Those products have their place, but structural bolts offer flexibility for larger projects. Take cross-laminated timber, or CLT, which is the fastest-growing mass timber material in North America right now. CLT panels are made by gluing layers of wood at right angles, creating a flat, solid panel that can be used for floors, walls, and roofs in mid-rise buildings (up to 18 stories, per current IBC). For attaching CLT panels to steel beams, or connecting CLT shear walls to each other, structural bolts are often the go-to because they can handle both vertical loads (weight from the floor above) and lateral loads (wind or seismic force) without the need for complicated hardware. In 2021, we supplied bolts for a 12-story CLT office building in Portland, Oregon, that used 1.25-inch stainless steel A490 bolts to connect floor panels to the building’s glulam core. The engineering team there chose bolts because they could adjust the spacing on-site as they tweaked the building’s load calculations, a flexibility that small specialized fasteners don’t offer.
Of course, using structural bolts in wood isn’t as simple as grabbing any bolt off a shelf. There are non-negotiable engineering rules that come with it, which is why as a supplier, we don’t just sell bolts—we spend 30 minutes with every wood builder who reaches out, walking through their project specifics. First, you have to match the bolt material to the wood’s environment. If the structure is in a humid area, like the Pacific Northwest, or near salt water (think coastal cabin or deck), galvanized bolts will corrode over time, and corrosion weakens the bolt’s tensile strength. We spec 316 stainless steel bolts for all coastal or high-humidity projects, even though they cost 20% more upfront, because we’ve seen what happens when cheap, non-stainless bolts corrode: a 2019 project in Maine where deck structural bolts corroded so badly after 5 years that the deck sagged, requiring a full rebuild. On the flip side, for a dry, inland structure like a Colorado mountain cabin, hot-dip galvanized A325 bolts work perfectly, at a lower cost.
Second, load calculations are non-negotiable. You can’t just hammer a bolt into a timber and hope it works. You need to calculate the total load the connection will carry: dead load (the weight of the wood itself, roofing, flooring), live load (people, furniture, snow), and lateral load (wind, earthquakes). Our engineering team has a simple formula we walk builders through: for a typical wood post-to-beam connection, each structural bolt will carry roughly 1,200 pounds of shear load (for A325 bolts) if installed correctly. If your connection needs to hold 6,000 pounds, you need 5 bolts, spaced properly, not 3. I’ve seen too many builders cut corners here, using too few bolts to save money, and that’s when failures happen. Last year, a small home builder in Michigan called us after a 20-foot glulam beam he’d bolted to a post shifted 2 inches during a winter snow load. He’d only used 2 bolts instead of the 5 his engineer specified, cutting his fastener costs by $180. The repairs, including new bolts, reworking the beam, and structural inspections, cost him over $12,000. That’s a mistake he’ll never make again.
Another key point: structural bolts work for both new builds and retrofits, which is a huge win for older wood structures. If you own a 100-year-old barn that’s showing signs of sagging beams, adding structural bolts to the joints can reinforce the structure without tearing apart the entire barn. We supplied bolts for a historic timber frame barn in upstate New York in 2020, where the owner wanted to keep the original look of the beams but add enough strength to use the barn for wedding events. Instead of drilling big holes through the visible part of the beams, we suggested lag-in structural bolts that go through the side of the timber, hidden behind trim, so the historic look stayed intact while the connection load increased by 40%. That’s a solution that specialized wood fasteners can’t offer, because they’re designed to be visible or used on new builds, not retrofits where aesthetics matter.
I know some of the purists will push back, saying that traditional wood joinery—mortise and tenon, dovetails—are the only “authentic” way to build a wooden structure. But authenticity doesn’t equal safety or longevity. A mortise and tenon joint can be strong, but if it’s not reinforced after years of shifting, it can come apart. Structural bolts, when installed correctly, don’t shift—they hold their tension for decades, even in fluctuating temperatures and humidity. That’s why we’ve seen more and more custom timber frame builders, CLT manufacturers, and even historic preservationists reach out to us in the last 5 years. The demand for mass timber is growing as the industry pushes for more sustainable building materials (wood absorbs carbon, while concrete and steel are high emitters), and structural bolts are the piece that makes those big wood builds safe and code-compliant.
Let’s be clear: I’m not saying structural bolts should replace every wood fastener. For small projects, like a 10×12 shed or a backyard bench, lag screws or even quality exterior screws are more than enough, and they’re easier for DIY builders to install. But for any structural wood build—whether it’s a mid-rise office, a post-and-beam home, a historic barn retrofit, or a commercial deck that will hold thousands of pounds of people and equipment—structural bolts are the most reliable, cost-effective choice.
After 12 years in this business, the biggest lesson I’ve learned is that the best building solutions don’t have to be new or trendy—they have to work. Structural bolts have been around for over a century, used in everything from bridges to skyscrapers, and adapting them for wood structures isn’t a gimmick, it’s a smart adjustment that opens up new possibilities for sustainable, strong wood builds.
If you’re planning a wood structure project, whether it’s new construction, a retrofit, or a custom timber frame, don’t guess when it comes to fasteners. We’ve helped hundreds of builders and architects spec the right structural bolts, tailored to their project’s load, environment, and budget, and we can help you too. Contact us to discuss your project details, share your load calculations, and get a quote that keeps your structure safe for decades to come.
Socket Head Cap Screws References
American Institute of Timber Construction. (2022). Timber Construction Manual (6th ed.). John Wiley & Sons.
International Code Council. (2021). International Building Code. International Code Council.
American Society for Testing and Materials. (2019). Standard Specification for Carbon Steel Bolts and Studs, 60,000 PSI Tensile Strength (ASTM A325). ASTM International.
Forest Products Laboratory. (2018). Wood Handbook: Wood as an Engineering Material. U.S. Department of Agriculture.
Handan Jihao Fastener Co., Ltd.
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