Type 17 roofing screws are a specialized fastener designed to secure metal roofing and siding panels. They combine a weather-resistant coating, a sharp self-drilling tip, and a hardened threading pattern to ensure firm attachment and long service life. Understanding their differences in material, coating, and drive type helps builders choose the right screw for durability and performance in various climates. This guide covers what Type 17 screws are, how they work, and how to select and install them correctly for American roofing projects.
What Are Type 17 Roofing Screws
Type 17 roofing screws are self-drilling fasteners specifically engineered for metal roof panels and related junctions. The distinctive Type 17 recess is designed for a Philips-style drive that resists camming and provides reliable torque. The screw typically features a sharp point, aggressive thread, and a sealing washer to prevent water intrusion at the panel’s seam. These screws are intended for direct fastening into metal substrates like steel, aluminum, or galvanized steel, with attention to the manufacturer’s recommended substrate thickness.
Key characteristics include a self-drilling tip that eliminates pre-drilling, a durable coating to resist corrosion, and a joint-sealing washer to minimize leaks. The head style and washer diameter are chosen to balance load distribution, water sealing, and panel appearance. In practice, Type 17 screws are among the most common choices for exposed-fastener metal roofing systems in the United States.
Common Materials And Coatings
Screw material directly influences corrosion resistance and durability. Common options include:
- Stainless Steel: Excellent corrosion resistance, ideal for coastal or highly corrosive environments. Higher in cost but longer-lasting.
- Carbon Steel With Coatings: A baseline option with protective coatings such as ceramic, ceramic-coated, or zinc-aluminum blends for enhanced weather resistance.
- Zinc Aluminum Alloy (ZAM) Coatings: Balanced performance and cost, good for many residential climates.
- Polymer or Nylon Seals: Some washers use integrated seals or polymer finishes to improve waterproofing and reduce loosening from vibration.
Coatings like ceramic or ceramic-enhanced coatings offer high resistance to ultraviolet light and weathering, extending the life of exposed fasteners on sunny regions. When choosing screws, align material and coating with the roof environment, panel thickness, and anticipated thermal cycling.
Sizes And Thread Types
Type 17 screws vary primarily by length, gauge, and thread design. Typical considerations include:
- Length: Length must penetrate through the metal panel and into the substrate enough to resist pull-out, but not so long as to pose a risk of interior damage. Common lengths range from 1 inch to 1-1/4 inches for standard metal roofing.
- Diameter (Gauge): Affects shear strength and driving torque. Heavier gauges suit thicker panels and stronger substrate engagement.
- Thread Pattern: Coarse versus fine thread affects grip in different substrate materials. Coarse threads are common for thin or soft metals, while fine threads suit harder substrates.
- Driving Style: Phillips drive is common for Type 17, but some variants use square drive or star drives for improved torque transfer and reduced cam-out.
Always verify the panel profile, substrate material, and climate conditions when selecting length and gauge. Following the manufacturer’s recommendations ensures proper sealing and load performance.
Applications And Best Practices
Type 17 screws are widely used for:
- Attaching metal roofing panels to purlins or roof decks.
- Securing metal siding and soffit systems in residential and light commercial projects.
- Sealing and fastening through panels at ridge lines or eave details when a watertight seal is required.
Best practices include:
- Avoid overtightening, which can warp panels or crush seals. Use a torque-limiting drill or a shallow setting when attaching with a power driver.
- Use a properly sized sealing washer to maximize waterproofing at panel joints.
- Maintain uniform screw spacing along the panel to distribute load and minimize leaks.
- Coordinate with underlayment and flashing details to ensure continuity of weatherproofing.
In regions with freeze-thaw cycles or heavy snowfall, ensure screws are rated for thermal movement and potential icing effects. For coastal areas with salt spray, stainless steel screws may offer superior longevity despite higher upfront costs.
Installation Tips And Techniques
Effective installation enhances performance and reduces maintenance. Consider these practical tips:
- Pre-check Materials: Inspect screws for coating integrity and drive compatibility before use. Replace any damaged items.
- Pilot Considerations: Although Type 17 screws are self-drilling, verify substrate thickness and avoid striking hidden components like electrical conduits or framing members.
- Sealant Compatibility: Ensure washers and gaskets are compatible with the chosen sealant or weatherproofing system to prevent chemical reactions or corrosion.
- Pattern And Spacing: Follow manufacturer guidelines for row spacing and panel overlap. Improper spacing can lead to wind uplift failures or leaks.
- Driving Technique: Use a steady, even pressure. Avoid sudden bursts of torque that can strip threads or twist the washer.
For retrofit projects, match the existing panel thickness and substrate to the screw length. When in doubt, consult the panel manufacturer or a licensed roofing professional to validate the fastener selection.
Maintenance And Replacement
Maintenance extends the life of a roof secured with Type 17 screws. Regular checks should include:
- Inspecting exposed fasteners for rust, discoloration, or looseness.
- Replacing any screws showing corrosion or backing out due to thermal movement or wind loads.
- Ensuring washers remain intact and effective at sealing points along panels and seams.
- Re-sealing or flashing replacement when signs of water intrusion appear around fastener sites.
When replacing screws, reuse existing pilot holes only if the panel material and substrate allow. Otherwise, re-drill with the appropriate length and thread configuration to maintain sealing and structural integrity.
Choosing The Right Type 17 Screw For Your Roof
Selecting the correct Type 17 screw involves evaluating panel material, substrate thickness, environmental conditions, and budget. A high-visibility coastal installation with salt exposure may justify stainless steel screws with a premium coating. For inland or temperate climates, galvanized or ZAM-coated screws often provide a favorable balance of cost and performance. Align your choice with the roof profile, panel width, and the anticipated load from wind, rain, and snow. In all cases, follow the roofing system manufacturer’s recommendations to maximize warranty coverage and long-term performance.