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The most common and recommended screws for joist hangers are:
- #9 x 1-1/2 in. pan-head, self-drilling screws
- #10 x 1-1/2 in. hex washer-head, self-drilling screws
- #10 x 3 in. hex head, self-drilling screws (for heavy duty applications)
You want to use corrosion resistant screws that are compatible with both the joist hanger material and the joist material. Stainless steel and coated screws provide corrosion resistance.
Joist hangers are metal brackets used to attach joists to headers or beams in residential construction. They provide a strong connection between the structural members and help transfer loads properly. Choosing the right type and size of screws for joist hangers is important to maintain the integrity of the connection.
This article will discuss the key factors to consider when selecting screws for joist hangers, the most common types and sizes used, and provide examples of appropriate screw choices for different joist hanger applications. Properly installed screws are critical for the joist hanger to function as intended and prevent structural issues down the line.
Matching Screw Type to Joist Hanger and Joist Materials
Joist hangers are made from various materials including steel, stainless steel, and galvanized steel. The joists themselves may be wood, engineered wood, or steel. The first consideration when choosing joist hanger screws is making sure the screws are compatible with the metals used for the specific hanger and joist.
For steel hangers and wood joists, use coated or stainless steel screws. The coating, often mechanically galvanized or ceramic coating, provides corrosion resistance when paired with the steel hanger and wood joist.
For stainless steel hangers, choose stainless steel screws. Stainless matches the corrosion resistance of the hanger.
For steel joists, use coated or stainless steel screws that are self-drilling. The screws need to be able to drill their own pilot hole through the steel.
Common Joist Hanger and Joist Material Combinations
| Joist Hanger Material | Joist Material | Recommended Screw Type |
|---|---|---|
| Galvanized Steel | Wood | Mechanically galvanized or ceramic coated steel |
| Stainless Steel | Wood or Steel | Stainless Steel |
Screw Size
The most common screw sizes used for joist hangers are:
– #9 x 1-1/2 in.
– #10 x 1-1/2 in.
– #10 x 3 in. for heavy duty applications
The screw must be long enough to penetrate through the joist hanger into the joist by a minimum of 1 inch. 1-1/2 inch and 3 inch screws meet this requirement for most residential joist hangers.
The larger #10 diameter screws are stronger and recommended for heavy loads. The smaller #9 screws are suitable for lighter loads.
Use the manufacturer’s recommendations to select the appropriate screw size for the specific joist hanger and span.
Recommended Screw Sizes for Joist Hangers
| Joist Hanger Type | Screw Size |
|---|---|
| Light duty (up to 500 lb span) | #9 x 1-1/2 in. |
| Standard duty (500 lb to 2100 lb span) | #10 x 1-1/2 in. |
| Heavy duty (over 2100 lb span) | #10 x 3 in. |
Screw Head Type
The most common screw head types used are:
– Pan head
– Hex head
– Hex washer head
Pan head screws sit flush with the joist hanger once installed. The flat head provides a lower profile.
Hex head and hex washer head screws have larger heads to grip the screw and prevent spinning when driving the screw in. The hex shape allows for proper wrenching.
Hex washer head screws have a built-in washer under the head for extra bearing surface against the steel.
Recommended Screw Head Types
| Application | Recommended Screw Head |
|---|---|
| Thin joist hangers | Pan head |
| Heavy duty joist hangers | Hex head or Hex washer head |
Pan heads are prone to spinning in heavy duty hangers. Hex heads offer more grip and driving power.
Self-Drilling vs Standard Wood Screws
Self-drilling screws, as the name implies, drill their own pilot hole before driving the screw into the material. The tip is specially designed to penetrate steel and wood without a pre-drilled hole.
Standard wood screws require a pilot hole to be drilled first before installing the screw.
For attaching joist hangers, self-drilling screws are preferred because:
– They are designed for use with steel hangers and wood joists.
– They provide better precision when aligning the hanger and joist. The screw pulls the two materials tight together.
– Installation is faster without needing to pre-drill pilot holes.
Wood screws take more effort to use since each hole must be pre-drilled. The fit is also not as snug when driving the screws in.
Corrosion Resistant Coatings
Coatings help protect steel screws from corrosion when used with steel hangers and exposed to weather. Two common types of coatings are:
Mechanically Galvanized – This applies a zinc coating to the screws using a mechanical process to bond the zinc to the steel. Provides good corrosion resistance.
Ceramic Coating – A ceramic material is coated onto the screws to shield against moisture. Provides extra protection versus galvanized.
Stainless steel screws offer the best corrosion resistance but are more expensive. Coated screws provide decent corrosion protection at a lower cost.
Conclusion
Choosing the optimal joist hanger screws involves matching the screw and materials being fastened, proper sizing based on load, appropriate head style, self-drilling, and corrosion resistant coated options.
The key is using screws designed for joist hanger connections, with sufficient length, diameter, and corrosion protection. Following manufacturer recommendations for sizing and using quality screws ensures the joists are securely attached and able to handle required structural loads.