Rafter Screws: Do They Meet Code? (SDWC Load Ratings vs. Ties)

Rafter screws — also called truss screws — replace hurricane ties by driving straight through the rafter or truss into the top plate, and a two-screw connection like the Simpson SDWC Truss screw rates 905 lb of uplift resistance in Douglas Fir/Southern Pine framing. Under IRC R802.11.1, an engineered uplift connector is only required once wind uplift exceeds 200 lb or rafter spacing tops 24 inches on center. This guide covers code-listed screw options, how they compare to hurricane ties, and how to install them.

What Are Rafter Screws?

Rafter screws are fully-threaded structural wood screws that create a rated connection between a rafter or truss and the top plate it sits on. Unlike common nails or general-purpose deck screws, they carry a code evaluation report — the Simpson SDWC Truss screw, for example, is listed under IAPMO-UES ER-262 — that documents tested allowable loads, which is what lets them legally replace a hurricane tie in many framing conditions.

They are not interchangeable with general-purpose wood screws you’d use for the kind of screw selection and drilling work covered elsewhere on this site — mixing them up means the connection no longer matches any tested load, and it won’t pass inspection where an uplift connector is required.

Do Rafter Screws Meet Code?

Yes — but only screws that carry a current code evaluation report. The Simpson Strong-Drive SDWC Truss screw is listed under IAPMO-UES ER-262 and tested to ICC-ES acceptance criteria AC233 (screw) and AC13 (roof-to-wall connection), meeting 2018 and 2021 IRC and IBC requirements. A generic hardware-store wood screw with no evaluation report does not meet code for this connection, regardless of its length or diameter.

When Do You Actually Need an Uplift Connector?

Per IRC Section R802.11.1, an engineered uplift connector — a rated screw or a hurricane tie — is only required where the calculated wind uplift force exceeds 200 lb, or where rafters or trusses are spaced more than 24 inches on center. Below that threshold, the toe-nailing schedule in Table R602.3(1) is sufficient on its own. Above it, code requires a tested connection, and rafter screws and hurricane ties both qualify — provided the specific product’s allowable load meets or exceeds the calculated uplift for your wind zone.

Rafter Screws vs. Hurricane Ties: Uplift Numbers Compared

Rafter screws don’t automatically out-perform a hurricane tie — it depends on the specific product and configuration. Here’s how the allowable uplift loads actually compare, pulled from each manufacturer’s current evaluation data:

Connector	Allowable Uplift	Install Notes	Best For
SDWC Truss screw, 2-screw (DF/SP)	905 lb	No bracket, drives from inside the attic	Retrofits, tight attic access
SDWC Truss screw, 2-screw (SPF/HF)	850 lb	Same as above, softer framing species	Spruce-pine-fir framing
Simpson H1 hurricane tie	480 lb	Visible bracket, 8–10 nails per tie	New-build framing, lowest cost per tie
Simpson H1A hurricane tie	Higher than H1 (mfr-rated)	Redesigned gauge/nail pattern	High-wind zones needing more than 480 lb from one tie

Uplift values are allowable loads from each manufacturer’s current evaluation report, not a guaranteed rating for every install — always confirm against the report for your exact species and configuration.

📊 A two-screw Simpson SDWC Truss connection is rated for 905 lb of uplift (DF/SP) — nearly double the 480 lb allowable load of a standard Simpson H1 hurricane tie. — Source: Simpson Strong-Tie, SDWC Truss Screw product data

A two-screw SDWC connection outperforms a single H1 tie on paper, but it also costs more per connection and doesn’t give you the visual, at-a-glance inspection point a metal tie does. Many builders use screws for retrofits and tight attic access, and ties for new construction where the bracket is easy to nail before the roof sheathing goes on.

Choosing the Right Rafter Screw

Structural rafter screws typically run a 0.15–0.22 inch shank diameter (roughly a #9 to #14 screw gauge) in lengths from 4 to 8 inches, depending on the rafter and top-plate thickness you’re joining. That’s noticeably thinner than the 1/4 or 5/16-inch lag-bolt-style hardware some guides recommend — structural screws hold their rating through thread engagement and hardened steel, not raw bulk.

• Length: long enough to fully penetrate the top plate without blowing through the bottom, typically 6 inches for standard 2x framing.
• Material and coating: stainless steel for coastal or treated-lumber applications; a corrosion-resistant coating like clear zinc with an orange topcoat for standard interior framing.
• Load capacity: always taken from the manufacturer’s evaluation report for your exact wood species (DF/SP vs. SPF/HF), not a generic spec sheet number.
• Drive system: Torx (T30 on most SDWC sizes) resists cam-out and stripping better than a Phillips or slotted head under high driving torque.

Most structural rafter screws are self-tapping and skip a pilot hole, but if you’re pairing them with a general wood screw elsewhere in the same connection, match the bit to the shank the same way our pilot-hole drill size guide lays out for standard wood screws. If you’re sizing screws for a different connection — subfloor, not roof framing — see our guide to subfloor screw spacing instead, since the load path and code section are both different from a rafter-to-plate uplift connection.

How to Install Rafter Screws

1. Confirm the load and pick a code-listed screw: Calculate the wind uplift for your rafter spacing and check the screw’s evaluation report to confirm its allowable load meets or exceeds that number.
2. Position the screw: Center it on the rafter face about 2 inches up from the seat cut, angled to catch both the rafter and the top plate below.
3. Drive with the correct bit: Use the manufacturer’s specified drive bit — T30 Torx for the SDWC Truss screw — at a slow, steady RPM; most structural screws are self-tapping and skip the pilot hole in standard framing lumber.
4. Set the head flush: Stop driving once the head contacts the wood surface. Overdriving can strip the connection and reduce the rated load.
5. Add a second screw where required: A two-screw configuration roughly doubles the single-screw allowable load — check the product’s load table to confirm the two-screw rating meets your calculated uplift.

“We always keep a structural screw at least 2 inches off the end of the board and centered on the rafter face — a Type-17 self-tapping tip cuts its own threads well, but crowd it too close to end grain and it can still split even treated lumber.”

Common Mistakes to Avoid

• Using a non-structural wood screw: it has no evaluation report and no documented uplift rating, so it won’t pass inspection even if it “feels” tight.
• Guessing at the uplift load instead of calculating it: the number that decides whether you need one screw, two screws, or a hurricane tie comes from your wind zone and rafter spacing, not a rule of thumb.
• Driving too close to the board end: keep at least 2 inches of clearance from end grain, even with a self-tapping tip, to avoid splitting.
• Mixing screw ratings from different manufacturers on the same job: an SDWC’s 905 lb rating doesn’t transfer to a different brand’s screw — check that product’s own report.

Uplift is only one load path to check — if you’re also confirming a rafter or beam can carry its span and snow/roof load, our wood beam load capacity guide walks through that separate calculation.

Frequently Asked Questions on Rafter Screws

What screws are used for rafters?

Code-listed structural screws are used for rafters — most commonly the Simpson Strong-Drive SDWC Truss screw or an equivalent engineered fastener like FastenMaster TrussLOK. These carry a current ICC-ES or IAPMO-UES evaluation report listing tested allowable loads, which a general-purpose wood screw does not have.

Do truss screws meet code?

Yes, when the specific product carries a current evaluation report. The Simpson SDWC Truss screw is listed under IAPMO-UES ER-262 and tested to ICC-ES AC233 and AC13, meeting 2018 and 2021 IRC and IBC requirements for truss and rafter-to-top-plate connections in most wood-framed buildings.

What are truss screws?

Truss screws are fully-threaded structural wood screws designed to connect a truss or rafter directly to the top plate it bears on, replacing a hurricane tie or clip. The full-length thread and hardened shank give them a rated pull-out and shear strength documented in the manufacturer’s code evaluation report.

How do you install rafter screws?

Position the screw on the rafter face about 2 inches from the seat cut, angled to catch both the rafter and the top plate below, then drive it with the manufacturer’s specified bit until the head sits flush. Most structural screws are self-tapping and don’t need a pilot hole in standard framing lumber.

Can you use regular wood screws instead of rafter screws?

No. Regular wood screws have not been load-tested for this connection and carry no evaluation report, so they typically fail well below the uplift resistance of a code-listed structural screw and won’t pass inspection where an engineered connector is required.

Conclusion

A code-listed rafter screw like the Simpson SDWC Truss screw gives you a documented, inspectable connection — 905 lb of uplift resistance from two screws in DF/SP framing — without the bracket and nail pattern a hurricane tie needs. Whichever you choose, the deciding number is your calculated wind uplift against the product’s own evaluation report, not a general claim that one method beats the other.