Simpson Strong-Drive Structural Screws: SDWS, SDWH, and SDWC Explained

Drilling a pilot hole and threading in a lag bolt used to be the standard move for structural wood connections. And it worked. But it was slow. If you're running through a stack of ledger connections on a deck or laminating beams on a framing job, stopping to pre-drill every fastener adds up fast. Then there's the splitting risk on edge grain and dry lumber, which nobody needs in the middle of a job.

Simpson's Strong-Drive structural screw line changes that equation. The SDWS, SDWH, and SDWC aren't just boxes of construction screws from the hardware store. These are code-listed fasteners that go through independent testing for shear loads and withdrawal values — the same way a joist hanger or a holdown does. If you're on a permitted project, that distinction matters.

This guide covers all three series: what they're built for, what's different between them, how to pick the right coating, what tools you're going to need, and which products TotalFastening.com carries so you can order exactly what the job requires.

Robert Falk, a structural engineer at the U.S. Forest Products Laboratory, spent years reviewing newspaper coverage of deck collapses. What he found was consistent. As he told This Old House: "Nearly every collapsed deck had been attached with nails, rather than bolts, and investigators had pinpointed the nails as the cause of collapse."

The holding power difference is real. According to the GuideOne Center for Risk Management, lag bolts provide as much as nine times the pullout resistance of a nail. Structural screws hit comparable or better numbers — and they install faster without the pilot hole requirement.

The Consumer Product Safety Commission tracked about 224,000 deck and porch injuries between 2003 and 2007. Roughly 15 percent of those came from a structural failure or collapse. That's not a reason to panic — it's a reason to use the right fastener and know why it's rated for the connection you're making.

NADRA (the North American Deck and Railing Association) estimates that of the more than 60 million decks in the U.S., about 30 million are past their useful life. A lot of those were built with fasteners that don't hold up over decades of moisture cycling and load. Structural screws won't fix an old deck — but on new construction, they give you a connection that's tested and code-listed from day one.

The term "structural screw" gets used loosely in the trades. What sets Simpson's Strong-Drive line apart is the code listing. The SDWS and SDWH screws are listed under IAPMO-UES ER-192 and ICC-ES ESR-2236, which means an independent testing body has reviewed the load values and approved them for use under the 2018, 2021, and 2024 editions of the IRC and IBC.

That's not true of most construction screws. A lot of what you'll find at a big box store is fastener-grade material without published load tables and without a code report behind it. If you're building something that gets inspected, a structural screw with a code listing gives you and the inspector something to point to.

Simpson makes three families: the SDWS timber screw, the SDWH timber-hex screw, and the SDWC truss screw. They're not interchangeable — each one is engineered for specific applications, and picking the wrong one means you're not getting the rated load capacity you need.

The SDWS Timber Screw is what most people are talking about when they mention Simpson structural screws. The standard version runs 0.220 inches in shank diameter — larger than a construction screw, smaller than a lag bolt — and uses a flat countersinking head. You drive it with a T40 bit.

The feature that makes this screw worth talking about is the SawTooth point. It's a patented design that bites into the wood surface and self-drills without a pilot hole. It also reduces the torque needed to drive the screw, which cuts down on splitting — especially on edge grain and near the ends of boards.

In their 2024 press release announcing the black double-barrier coating option, Simpson described it this way: "The knurled shank and patented SawTooth point ensure fast starts, reduce installation torque, and eliminate the need for predrilling in most applications. The double-barrier coating delivers corrosion resistance equivalent to hot-dip galvanization, making it suitable for certain exterior and preservative-treated wood applications."

Lengths run from 3 inches up to 15 inches depending on the variant. The framing version (0.160-inch shank, T25 drive) is lighter-duty for general framing connections and connector-to-wood attachments. For coastal or marine environments, the 0.275-inch stainless version (T50 drive) is the spec.

Table 1 | 

The SDWH is Simpson's answer to the lag bolt — same structural job, different approach. Instead of a countersinking flat head, the SDWH uses a large hex washer head. You drive it with a socket: a 5/16-inch hex for the 0.195-inch shank version, or a 7/16-inch hex for the heavier 0.276-inch shank.

The hex head gives you more torque for driving into dense species or deep connections, and the large washer surface spreads the bearing load across the wood face so you don't need a separate washer. On a ledger board connection or a post-to-beam connection, that matters for the load distribution.

Like the SDWS, the SDWH uses the SawTooth point — no pilot hole in most applications. Lengths run from 3 inches up to 15 inches, which gives you enough penetration depth for heavy timber connections and multi-ply beam laminations.

The SDWH comes in three coating options. Double-Barrier Coating (tan) is your everyday exterior and treated-lumber option. Hot-Dip Galvanized (HDG) — found on the 0.276-inch diameter models with a "G" suffix — is the marine and coastal spec. Type 316 stainless steel is the highest corrosion resistance in the line, available in both shank sizes.

Table 2 | 

The SDWC is the odd one out in the Simpson structural screw family, and it deserves more attention than it usually gets. It's not built for ledger boards or heavy timber. It's designed specifically for truss-to-wall-plate and rafter-to-top-plate connections — the heel connection at the bearing point where a roof truss or rafter sits on top of a wall.

You know the debate about toe-nailing that happens on jobsites? The SDWC is the structural, code-listed answer to it. It's a 0.155-inch shank with a cap head — wide and low-profile for maximum bearing area — and a T30 drive. Two lengths: 4-1/2 inches and 6 inches.

The orange zinc color on the SDWC15600 models is worth noting. It's a code compliance indicator that lets an inspector verify the right fastener was used at the truss heel without having to pull samples. If you're in a high-wind zone, this one detail can speed up your inspection significantly.

Simpson also makes the SDWC-GUIDE, a metal installation jig that holds the screw at the correct angle for a heel connection. It's designed specifically for the SDWC15600. If you're running these on a production framing crew, the guide takes the guesswork out of angle consistency.

Table 3 | 

Getting the coating right isn't just about corrosion protection — it's about code compliance when you're using treated lumber. ACQ and CA preservative treatments are corrosive to standard zinc-plated fasteners, and using the wrong coating on a treated-lumber connection can cause accelerated corrosion that weakens the connection over time. Simpson makes it straightforward with three options.

The double-barrier coating (the tan "DB" and black "DBB" models) is Simpson's exterior-rated carbon steel option. It's approved for use with ACQ, CA, and CA-C treated lumber and provides corrosion resistance equivalent to hot-dip galvanization per Simpson's published specifications. The DB and DBB models are the same product — the only difference is color. The black finish is popular with contractors who want the hardware to blend into darker wood or stained lumber.

The HDG option appears in the SDWH 0.276-inch series (the "G" models). Hot-dip provides G185 zinc coating weight — heavier than most standard galvanized fasteners. If you're building near the ocean, on a dock, or anywhere with regular salt-air exposure, the HDG is your spec. One thing to watch: HDG fasteners require overtapped nuts or coupling hardware because the thicker coating changes thread tolerances.

316 SS is available across the SDWS, SDWH, and SDWC families. It's the highest corrosion resistance option in the line and the right call for coastal construction, treated lumber in pool enclosures, or any environment that sees persistent chemical exposure. It costs more than carbon steel. But a structurally rated screw that's corroded through is a failed connection — and a failed connection in a structural application isn't something you can ignore.

The drive type varies by series, so here's a quick reference for each one. Getting this right before you start means you're not stopping mid-connection to swap bits.

• SDWS Timber Screw (0.220"): T40 Torx bit. An impact driver works well for most applications. On dense wood or large-diameter lumber, a corded drill with higher torque gives you more control.
• SDWS Framing Screw (0.160"): T25 Torx bit.
• SDWS Timber SS (0.275"): T50 Torx bit.
• SDWH 0.195" models: 5/16" hex drive bit or socket. An impact driver with a hex bit adapter drives these efficiently.
• SDWH 0.276" models: 7/16" hex drive socket or bit.
• SDWC Truss Screw: T30 Torx bit. Use the SDWC-GUIDE installation tool for consistent angle at heel connections.

One note on impact drivers and the SDWC: the truss screw goes into thinner dimensional lumber near a top plate. Back off the torque setting on your impact driver or switch to a drill to avoid stripping the cap head or over-driving past the bearing surface. The cap head is designed to sit on the wood surface — it's not meant to countersink.

The SDWH is the practical choice for deck ledger attachment. IRC Table R507.2 specifies lag screw diameter and spacing requirements for ledger-to-rim-board connections — the SDWH 0.195-inch double-barrier or 0.276-inch HDG can substitute for the specified lag screw when installed per the load tables in Simpson's ESR-2236. No pilot hole in most lumber species means faster installation on a connection you're making repeatedly on every deck build.

Multi-ply beam laminations, post-to-beam bearing connections, and heavy timber framing are where the SDWS 0.220-inch timber screw and the SDWH 0.276-inch show the biggest time advantage over lag bolts. You're running the same connection over and over. No pilot hole needed, consistent seating depth, and the SawTooth point means you're not watching the wood split out near fastener ends.

The SDWC is the only Simpson structural screw specifically approved for truss-to-plate and rafter-to-top-plate connections. It's code-listed under ICC-ES ESR-3198. If you're framing in a high-wind or seismic zone and you're moving away from toe-nailed connections at the heel, the SDWC and SDWC-GUIDE are the tested, code-compliant option.

If you're on a permitted project, your inspector may ask for documentation on the fasteners you're using in structural connections. Simpson's SDWS and SDWH screws are listed under IAPMO-UES ER-192 and ICC-ES ESR-2236, both of which cover the 2018, 2021, and 2024 editions of the IRC and IBC. The SDWC truss screw is covered under ICC-ES ESR-3198. These aren't just marketing claims — they're independently reviewed evaluation reports that building officials reference during the approval process.

Derek Gilbert, a registered professional engineer and field engineer at Simpson Strong-Tie, noted in the company's structural engineering blog that concrete and masonry screw anchors — and by extension the company's structural fasteners — "have obtained evaluation reports, published by ICC-ES and IAPMO-UES, which building officials reference during the approval process." That review process is what separates a code-listed structural fastener from a box of construction screws.