What are Structural Screws? And Other FAQ
When it comes to building strong, long-lasting wood structures, the right fastener makes all the difference. Structural screws have quickly become a favorite among contractors and DIYers for their strength, ease of installation, and building code approval.
Whether you’re framing a deck, securing beams, or working on a timber-frame project, this FAQ will answer the most common questions about structural screws so you can choose the right product for the job.
What is a structural screw?
A structural screw is a high-strength fastener designed to replace nails, lag bolts, or carriage bolts in heavy-duty wood connections. They feature:
- Aggressive threads for maximum holding power.
- Coatings or stainless steel for indoor/outdoor use.
- Sharp points for quick, clean starts without pre-drilling in most cases.
They’re used for applications like deck ledger boards, post-to-beam connections, and timber framing.
What is the difference between a “Structural Screw” and a “Timber Screw”?
While the terms are often used interchangeably, there’s an important distinction:
- Structural Screws are engineered, code-approved fasteners tested for load-bearing applications such as decks, beams, and heavy timber construction.
- Timber Screws are heavy-duty wood screws that may be strong but aren’t always tested or certified for structural loads.
If your project requires building code compliance, always choose a screw with published load ratings and certification, such as ICC-ES or ESR approval.
Are structural screws as good as nails?
In many cases, they’re better, but it can always vary on preference. Structural screws have superior holding strength and resist pull-out far more effectively than nails. While nails still excel in some high-shear applications, screws are often preferred for their precision, durability, and long-term performance. For a more detailed comparison, check out our blog Nails vs. Structural Screws.
Are structural screws load-bearing?
Yes, when rated and certified for structural use. In particular, Simpson Strong Tie's structural screws undergo rigorous testing for both shear and tension loads, making them suitable for critical connections in decks, pergolas, post frames, and more. Always verify load ratings for your specific screw size and application.
How much weight can a structural screw hold?
This depends on factors like:
- Screw diameter and length
- Embedment depth into the wood
- The type of wood or engineered lumber
For example, a 1/4” diameter structural screw can support hundreds of pounds in shear or tension. Always consult the manufacturer's load tables for exact ratings.
Can I use structural screws outdoors?
Absolutely, just make sure the screw is rated for exterior use. Options include coated steel, hot-dip galvanized, and stainless steel. For coastal or marine environments, stainless steel offers the best corrosion resistance.
Do I need to pre-drill for structural screws?
Most modern structural screws are self-tapping, meaning they cut their own path into the wood. However, in dense hardwoods or engineered lumber, pre-drilling can help prevent splitting and make driving easier.
Can structural screws replace lag bolts?
Yes, and in many cases they’re faster and easier to install. Unlike lag bolts, structural screws often don’t require pre-drilling, saving time on large projects.
Do building codes accept structural screws?
Many structural screws are ICC-ES or ESR certified, meaning they meet strict building code requirements. Always check your local codes and confirm the screw you choose is approved for your application.
How do I prevent overdriving a structural screw?
Use a drill or impact driver with adjustable torque settings, and stop driving as soon as the head seats flush. Overdriving can strip the head or reduce holding power.
What’s the difference between coated, galvanized, and stainless steel structural screws?
- Coated Steel – Great corrosion resistance for most exterior projects.
- Hot-Dip Galvanized – Enhanced protection in high-moisture environments.
- Stainless Steel – Best for extreme conditions, such as near saltwater.
For the best results, always match your structural screw choice to your project’s environment, load requirements, and building code needs.
