How do you choose the right construction fastener?
Start with the governing document: the structural drawings, nailing schedule, connector load table, product evaluation report, or manufacturer installation instructions. Those documents define the fastener type, diameter, length, quantity, spacing, edge distance, embedment, material and finish that make the connection work. Do not begin at the hardware bin and work backward from what is available.
Then check the connection itself:
- Load direction: Is the fastener resisting pull-out, lateral load, uplift, or a combination?
- Members: What wood species, engineered wood, sheet steel, concrete or masonry is being joined?
- Geometry: Is there enough penetration, edge distance, end distance and spacing without splitting or breaking out the base material?
- Exposure: Will the assembly stay dry, get wet, contact preservative-treated wood, see coastal salts or encounter other corrosive materials?
- Installation: Does the approved detail require a pilot hole, a specific bit, hole cleaning, a torque procedure, or a particular connector hole?
Nails can resist withdrawal loads, lateral loads, or a combination, and the wood, nail and service conditions affect both modes. The USDA Wood Handbook explains these separate connection demands. That is why the useful field rule is not simply "nails for shear and screws for pull-out." It is: use the fastener and installation schedule evaluated for the actual joint.
Nails: specify dimensions, not just penny size
Penny designations are convenient shorthand, but they are not a complete structural specification. The USDA recommends specifying nail size by length and diameter because penny-size dimensions can vary among producers. Its fastening chapter also shows that common, box and threaded nails with the same penny designation can have different diameters.
In the USDA table for bright common wire nails, an 8d is 2 1/2 inches long and 0.131 inch in diameter, while a 16d is 3 1/2 inches long and 0.162 inch in diameter. A smooth box nail of the same nominal length is thinner: the table lists an 8d box nail at 0.113 inch and a 16d box nail at 0.135 inch. If a schedule calls for a 16d common, a 16d box is not the same fastener.
Shank form matters too. Smooth, annularly threaded and helically threaded nails do not have identical withdrawal behavior, especially as wood moisture changes. But that does not turn every roof or floor schedule into a universal ring-shank requirement. Follow the panel manufacturer, code table and project schedule for that assembly. For more context on panel selection and installation conditions, use the subfloor and sheathing guide.
Before production nailing, confirm the nailer is loaded with the specified length, diameter, head and shank. Set depth so the head lands as required by the assembly rather than assuming a deeply buried head is acceptable.
Screws: use published values for the actual joint
Threads can provide strong withdrawal resistance, but that alone does not establish lateral capacity, ductility or suitability for a structural connection. The USDA treats withdrawal resistance and lateral resistance as separate subjects for wood screws. Its withdrawal guidance says capacity depends on factors including wood specific gravity, threaded penetration and screw diameter.
A structural screw is not a generic construction screw with a heavier label. Use the exact product, diameter, length, quantity and installation pattern allowed by the plans, code report or manufacturer table. A listed screw may replace a lag screw, bolt or nail only where its published documentation covers that substitution and the real joint configuration. Predrilling also follows the product instructions and wood conditions; it is not safe to assume every structural screw is approved for installation without a pilot hole.
Deck screws belong where their product documentation permits them. Drywall screws belong in drywall systems. General-purpose deck, drywall and construction screws are not substitutes for specified framing nails or connector fasteners merely because they drive easily.
For any screw connection, check five items on the package or technical document: exact model, shank diameter, length, thread penetration, and approved substrate or connection. Add coating and material compatibility before using it outdoors or in treated wood.
Coatings and corrosion: match the whole exposure
Corrosion selection is more specific than choosing "galvanized or stainless." Wood treatment chemical, chemical retention, exposure, moisture and metal compatibility all affect selection. Simpson Strong-Tie identifies those variables in its corrosion guidance, and it says no single guideline addresses every corrosion combination.
For preservative-treated lumber, read the end tag or treatment documentation before choosing hardware. Simpson says standard G90 connectors may be used with certain listed treatments only when the wood is installed dry and remains dry in service. Its treated-wood FAQ gives different recommendations for exterior and higher-exposure conditions. The practical sequence is to identify the preservative, retention, use category and exposure, then select an approved connector-and-fastener system. Our pressure-treated lumber guide explains how those treatment details appear on the lumber.
Keep the fastener and connector materials compatible. Simpson advises using fasteners or anchors and connectors with similar electrochemical properties, or isolating dissimilar metals where an approved detail allows it. A stainless connector generally takes the specified stainless fastener; a galvanized assembly takes the fastener approved for that connector and exposure.
Do not promise a service life from coating color or a salt-spray number. Simpson states that the variables and available test standards do not support an accurate service-life prediction for a specific installation. Inspect exposed structural hardware at an interval appropriate to the exposure, and have significant or suspected corrosion evaluated.
Structural connectors and concrete anchors
A connector load table is an assembly specification, not a rating for the steel shape by itself. Simpson states that the specified quantity, type and size of fastener must be installed in the correct connector holes to achieve published loads. Its connector-hole guidance also says fastener material and finish matter. That rules out filling a hanger with whatever nail or screw happens to fit through the hole.
Hole shape changes the instruction. In the Simpson system, round, obround and square holes are filled unless a note says otherwise. Triangular holes are used when the designer specifies maximum nailing. Diamond holes are for temporary positioning and require no fastener. Product-specific notes can create exceptions, so use the page or table for the exact connector. Double-shear and alternate-fastener configurations may also require a minimum length or a load adjustment.
Concrete anchoring starts with the design and the approved product for the actual substrate. Confirm concrete strength and condition, anchor diameter, embedment, spacing, edge distance, hole diameter and depth, cleaning, installation tool and tightening procedure. An expansion anchor, adhesive anchor and concrete screw are not field-interchangeable solutions to one generic failure mode.
For example, the Simpson Titen HD Rod Coupler is limited to dry interior environments, and its instructions require a specified-diameter carbide-bit hole at least 1/2 inch deeper than required embedment. The product instructions say to clean the hole as directed, seat the head flush and use the coupler only once. That is a product-specific example, not a universal concrete-screw procedure; the design report and instructions for the selected anchor control.
Common fastener mistakes to stop before inspection
- Shopping by label instead of dimensions. A penny designation, screw gauge or package description does not replace the specified diameter, length and product model.
- Treating withdrawal and lateral capacity as the same number. Thread bite does not prove that a screw is approved for the joint load and deformation demands.
- Making a brand-blind connector substitution. Connector capacity depends on the tested fastener pattern, including type, size, quantity, holes, member materials and load direction.
- Filling every visible hole by habit. Simpson identifies triangular holes for designer-specified maximum nailing and diamond holes for temporary positioning, while other hole types have their own rules. Read the exact hole and fastener instructions.
- Assuming every treated board gets one universal coating. Treatment chemistry, retention, moisture and exposure can change the required metal or coating.
- Mixing connector and fastener metals without checking compatibility. Dissimilar metals plus moisture can accelerate galvanic corrosion.
- Overdriving without inspecting the assembly. For Simpson connectors and straps, the company allows no load reduction only under listed conditions, including that the nail head is not driven past flush with the metal face and the existing hole is not enlarged or torn. Those conditions are narrower than a blanket claim that overdriving is harmless.
- Using a concrete anchor outside its approval. Wrong hole geometry, embedment, edge distance, substrate or reuse can reduce capacity even when the anchor looks tight.
Construction fastener FAQ
Can I use structural screws instead of framing nails?
Only where the plans, code report or manufacturer data approve the exact screw and connection. Published withdrawal strength alone does not establish lateral performance or authorize a substitution.
Do all joist-hanger holes need a fastener?
No universal answer applies to every hole. In Simpson connector guidance, round, obround and square holes are generally filled unless noted otherwise; triangular holes apply to designer-specified maximum nailing, while diamond holes are for temporary positioning. Follow the exact connector table.
What fastener should I use with pressure-treated lumber?
Identify the preservative, retention, use category, moisture and exposure first. Then use the treated-wood supplier and connector or fastener manufacturer recommendations for a compatible system. Hot-dip galvanized and stainless are common recommendations, but they are not interchangeable in every connector or exposure.
Can I reuse a concrete screw anchor?
Follow the selected product instructions. The Simpson Titen HD Rod Coupler example in this guide is explicitly one-use only, but that does not establish a rule for every anchor product.