Types of Screws: Which One to Use and When

Updated September 2026 · Home Project Resources

There are about a dozen types of screws that cover almost every home project, and they sort into six families by what they bite into: wood screws, deck screws, drywall screws, sheet metal and self-drilling screws, masonry screws, and machine screws. Pick the family by the material, then pick the size by two numbers only: gauge (thickness) and length. A #8 x 2-1/2 inch coated deck screw and a #6 x 1-1/4 inch drywall screw look similar in the bin and behave nothing alike.

The most expensive mistake in this whole category is using drywall screws for structural work. They are hardened, brittle, and they snap under shear load. They belong in drywall and nowhere else.

Updated September 2026

Building a deck and need a real fastener count? Use our free Deck Calculator to turn your deck size and joist spacing into a screw count you can take to the store, instead of guessing at boxes.

Types of screws at a glance

Read that table by the second column. People usually shop by what the box says on the front. The better habit is to name the material you are driving into first, then the length, then the head.

How to read a screw: gauge, length, thread and point

A screw label like #8 x 2-1/2 in coarse thread, star drive, flat head, exterior coated is five separate decisions.

Gauge is diameter. The number sign gauge converts to inches with a simple formula: diameter equals 0.060 plus 0.013 times the gauge.

Length is measured differently by head type. A flat head or bugle head is measured overall, because the head sinks flush. A pan head, hex head or washer head is measured from under the head, because the head sits on the surface. That is why a 2 inch pan head buries slightly less than a 2 inch flat head.

The one-third, two-thirds rule. For two pieces of wood, roughly one third of the screw should be in the top piece and two thirds in the bottom. Attaching 3/4 inch stock to a 2x4? A 2 inch screw puts 1-1/4 inches into the framing, which is right.

Coarse thread versus fine thread. Coarse threads have fewer, deeper threads and grab soft material fast. Fine threads have more threads per inch and hold better in dense material without splitting it. Softwood, plywood, particleboard and MDF take coarse. Oak, maple and hard exotics take fine.

Point styles. A sharp point starts on its own in wood. A type 17 auger point has a small slot cut in the tip that clears chips and cuts the need for a pilot hole in most softwood. A self-drilling point is an actual miniature drill bit for steel.

Wood screws, deck screws and structural screws are not interchangeable

These three sit next to each other in the aisle and get swapped constantly.

Wood screws are partially threaded on purpose. The smooth shank under the head passes through the top board without gripping, so as the threads pull in the lower board, the two faces clamp together. Fully threaded screws cannot do this. If your joint keeps ending up with a gap, that is usually the reason.

Deck screws are wood screws built to survive weather and treated lumber. Modern pressure treated wood uses copper based preservatives that eat plain steel and thin electro plating. Use hot dip galvanized, stainless, or a polymer or ceramic coated screw the manufacturer specifically rates for treated lumber. For the full build sequence, our guide on how to build a deck walks through framing and fastening in order.

Structural screws are the newer category, and they are the useful one. They are engineered and code listed with published shear and withdrawal values, they usually need no pilot hole, and one of them can replace a lag bolt of similar size while driving in a fraction of the time. Ledgers, post to beam connections, stair stringers and heavy brackets are their territory. Look for an evaluation report number stamped on the box.

Lag screws still have a place for very heavy timber work, but they need a pilot hole for the shank and a smaller one for the threads. Skipping that splits the wood.

Drywall screws: the ones that cause the most damage

Drywall screws are hardened steel with a bugle head that dimples the paper without tearing it. That hardening makes them brittle in shear, which is the load a shelf, a railing or a deck board puts on a fastener.

Two lengths cover almost everything: 1-1/4 inch for 1/2 inch drywall and 1-5/8 inch for 5/8 inch drywall, both on wood framing. On steel studs, use fine thread drywall screws with a sharp or drill point.

A standard 4x8 sheet on framing at 16 inch centers takes about 32 screws, which is roughly one screw per square foot. The same ratio gives about 40 screws on a 4x10 sheet and 48 on a 4x12. Our page on drywall screws per sheet has the full spacing math, and how to hang drywall covers the order of operations.

If you take one rule from this article: never use a drywall screw to hang anything that carries weight.

Sheet metal, self-drilling and machine screws

Sheet metal screws are fully threaded with a sharp or blunt point, designed to cut their own thread in a pre-punched or drilled hole. Type A has a coarse thread and a sharp point for thin sheet. Type AB is the modern general purpose version. Type B has a blunt point and finer thread for thicker sheet.

Self-drilling screws, often called by the trade name for their tip style, carry a small drill flute on the end. They drill the hole, tap the thread and fasten in one motion. Steel studs, metal roofing panels, duct work and gutter hangers all use them. The tip is rated for a maximum metal thickness, so check the box before driving into anything heavy.

Machine screws have a uniform thread and a flat end, and they only work with a nut or a tapped hole. They show up in appliances, light fixtures, door hardware and mounting brackets. Common sizes in a house are #6-32, #8-32 and 1/4-20, where the second number is threads per inch. Light fixture crossbars almost always use 8-32, which is worth remembering next time you are on a ladder holding a fixture with one hand.

Masonry screws for concrete, block and brick

A masonry screw cuts its own thread into a pre-drilled hole in concrete, block, brick or mortar joints. The two common diameters are 3/16 inch and 1/4 inch, and each has a matched carbide bit size that ships in the box.

The rules that decide whether it holds:

1. Drill with the matched bit, not the nearest size you own.
2. Drill about 1/4 to 1/2 inch deeper than the embedment, so cuttings have somewhere to go.
3. Blow the dust out. Dust left in the hole is the single most common reason a masonry screw spins free.
4. Minimum embedment is usually 1 inch, maximum around 1-3/4 inches. Deeper is not stronger, it just risks stripping the thread you cut.
5. Keep away from edges. Anchoring within an inch or two of a slab edge or the face of a block can pop a cone of concrete out.

For anything that hangs overhead or carries a person, use a rated anchor with a published load value instead, and follow the anchor manufacturer's instructions exactly.

Screw head types and what each one is for

Drive types, ranked by how well they stay on the bit

Buy the bit that comes in the box. Star and square drives are sized (T20, T25, T27, and #1, #2, #3), and a bit one size off is what chews the head into a useless dimple.

Coatings, corrosion and treated lumber

Steel rusts, treated wood accelerates it, and dissimilar metals in contact corrode each other. Three practical rules:

• Indoors and dry: plain zinc plated is fine.
• Outdoors, treated lumber, or anywhere damp: hot dip galvanized, stainless, or a coating the maker rates for ACQ and copper azole treated wood.
• Cedar, redwood and coastal exposure: stainless. The tannins in cedar and redwood stain black around plain steel, and salt air destroys plating.

Do not mix aluminum with treated lumber. Aluminum flashing, aluminum trim and aluminum fasteners all corrode in contact with copper based preservatives. Use a barrier or switch materials.

Worked example: screws for a 12x16 foot deck

Say the deck is 12 feet by 16 feet, joists spaced 16 inches on center, 5/4 by 6 decking with a 1/4 inch gap.

• Deck area: 12 x 16 = 192 square feet
• Joists: the 16 foot run divided by 16 inches gives 12 spaces, so 13 joists
• Boards: actual board width 5.5 inches plus a 1/4 inch gap = 5.75 inches per course. 144 inches of width divided by 5.75 = 25.04, so 26 boards
• Screws: 26 boards x 13 crossings x 2 screws per crossing = 676 screws
• Rule of thumb cross check: 3.5 screws per square foot x 192 = 672 screws

Those two numbers agree, which is the point of doing both. Buy by the count, not the box, and add about 10 percent for drops and drivers. A #8 x 2-1/2 inch star drive coated deck screw is the standard choice for 5/4 decking; 2x decking moves you to 3 inch.

Fastener length for the framing itself is different again. Joist hangers take the specific structural nail or screw the hanger maker lists, never a deck screw.

Pilot hole sizes worth memorizing

The clearance hole goes in the top board only. It lets the shank slide through so the threads in the lower board pull the joint closed. Drill it whenever you are working in hardwood or near an end or edge, which is where splits start.

Five mistakes that show up on every project

1. Driving too deep. A screw sunk past flush in framing loses holding power and can snap the head. Set the clutch on your drill and test on scrap.
2. Using a worn bit. A rounded #2 Phillips bit strips heads and gets blamed on cheap screws.
3. Fine thread in softwood. It spins without pulling. Coarse thread grabs.
4. No pilot near an end. Anything within about 2 inches of a board end in hardwood needs a pilot hole.
5. Mixing metals outdoors. Plain steel in treated lumber will bleed black streaks down the wood within one season.

For the tools that make this easier, see our list of essential DIY tools, and if you are cutting the parts as well as fastening them, our guide to types of saws covers which saw makes which cut.

Frequently asked questions

Can I use drywall screws for wood projects?

No, not for anything structural. Drywall screws are hardened so they drive cleanly through gypsum, and that hardening makes them brittle. Under a sideways load they snap off flush with almost no warning. Use a wood screw, a cabinet screw or a structural screw instead.

What size screw should I use for 2x4 framing?

For attaching 3/4 inch material to a 2x4, a #8 x 2 inch screw is the usual answer. For fastening two 2x4s face to face, use a #9 or #10 x 3 inch. For structural connections that carry load, use a code listed structural screw and follow the listed spacing.

Do I really need a pilot hole?

In softwood with a type 17 auger point screw, usually not. In hardwood, near an end or edge, or with any screw thicker than #10, yes. A pilot hole is the difference between a tight joint and a split board that has to be replaced.

What is the difference between a deck screw and a wood screw?

Both are partially threaded and made to pull two boards together. The deck screw adds corrosion protection rated for treated lumber and outdoor exposure, usually a star drive, and often an auger point that avoids splitting. A plain wood screw in a deck will start bleeding rust stains in the first wet season.

Which screws work in pressure treated lumber?

Hot dip galvanized to the standard printed on the box, 304 or 316 stainless, or a polymer or ceramic coated screw the manufacturer specifically labels for ACQ and copper azole treated wood. Near salt water, use 316 stainless. Do not use plain zinc plated or aluminum.

How many screws do I need per deck board?

Two screws at every joist crossing. A 16 foot board over joists at 16 inch centers crosses 13 joists, which is 26 screws per board. Across a whole deck that comes out to roughly 350 screws per 100 square feet. Run your own numbers with the Deck Calculator.

Are star drive screws actually better than Phillips?

Yes, for driving. The Phillips drive was designed to cam out under torque, which was useful with old clutchless drivers and is just annoying now. A star or square drive holds the screw on the bit one handed, takes more torque before slipping, and does not chew up the head. That is why nearly every premium deck and structural screw ships with a star bit.

What screw should I use to hang a heavy mirror or a TV?

Into studs, use a #10 or 1/4 inch lag or structural screw long enough to reach at least 1-1/2 inches into solid framing. Into drywall alone, use a rated toggle or anchor sized for the load, never a drywall screw. Our guide on how to hang a TV covers finding the studs and checking the bracket pattern first.