Deck screws hold decking boards together on a deck, porch, dock, or boardwalk as part of your home improvement. Choosing the best screws for deck boards is critical when building or repairing a deck.
Choosing the diameter of the screw and the length of your deck is critical. The optimum screw size ensures a secure and long-lasting hold. However, determining the optimum deck screw size for your project might be difficult.
So, you can easily ask, what decking screw size do I need? For example, 2×6 decks are typically 1.5 inches thick, and as you need 1 inch of penetration, 2.5-3 inch deck screws are suitable.
However, things change when treating lumber or using non-treated wood screws. For example, treated wood screws and pressure-treated timber are used in coastal locations; salt exposure or chloride from around a pool can cause corrosion.
You can learn what size screws for deck framing you need in our guide. By the end, you’ll see you need multiple sizes for the deck boards, rim joist, hurricane ties, and more. Using a screw sizes chart, getting the right decking screws is a cinch. (Read Flat Head Screwdriver Sizes Charts)
What Size Screws Should I Use For A Deck?
Different sizes of the screws will be the right deck screws depending on the areas you are fixing. Here are the areas and the structural wood screws you may need.
Deck Boards
Working with deck boards should be calm and secure. So choose beautifully coated screws. Screws for boards should be 2.5-3 inches long. Also, the diameter of your lag bolt shouldn’t exceed #8 or it may split.
Railing Posts
Deck railing screws with a diameter of 1/2 inches are ideal. It would be nice if the screws were galvanized for extra durability. Deck railing screw length should be roughly 6 inches long for 4×4 rails to secure the rim joist.
Post to Beam
To attach the post to the beam, use galvanized coated screws and galvanized post caps. Screws should be 2.5 inches or #10 in diameter. You’ll also need bracket-specific screws. Ensure the screw has a higher load rating for safety.
Joist to Beam
The ideal screws connecting the joist to the beam are #10 in diameter. The screw length should be 1.5 inches long for the convenience of use. Consider the hurricane tie while choosing joist to beam screws.
Stairs
You can use standard deck screws for the steps in your deck project. The # diameter coated screws fit nicely besides using pressure-treated screws.
Also, the same screws can be used for cedar wood stairs when deck building.
What Size Is A #10 Deck Screw?
It’s not always easy to choose the correct size of wood screws for your tasks. Other variables like wood type, screw material, lateral vs. shear stresses, and pilot holes add to the complexity.
Fortunately, there are some fundamental recommendations to assist you in selecting and using the right
type of screw for the job. (Read Lag Bolt Sizes Chart)
Length, Gauge, and Pilot Hole
Knowing a few basic rules about wood screws will help you choose the right one.
Length: Wood screws must be long enough to correctly hold the two boards together. If the screws are too short, the boards may not be sufficiently held together. They will piece through to the other side if they are too long.
Thickness (gauge): Wood screws must have enough thickness (gauge) to grip the two boards. The screw may pull out of the wood if it is too thin. On the other hand, the screw may fracture the wood if too thick, rendering it worthless.
Pilot holes: Drilling a pilot hole with a standard bit or a countersink bit before driving the screw is usually a good idea in hardwoods. Hardwoods like oak and walnut are prone to splitting, whereas softwoods like pine and cedar are less prone.
Friction and the pressure of wood fibers holding the threads give wood screws their strength.
When fibers are cut away and removed, a pilot hole can diminish the grip of the wood surrounding the screw threads, lowering the screw’s holding power.
Lateral vs. Withdrawal Load
To hold tight, wood screws and lag bolts must have enough thread pushed into the receiving stock.
The length of the thread and the thread size in the receiving board are determined by the forces applied to the boards when in use, be it lateral or withdrawal forces.
- Lateral loads: Consider using a thicker (larger thread size and diameter) screw than you may otherwise choose if the forces will apply lateral pressure, often known as sheer pressure.
- Withdrawal loads: If the forces will create withdrawal pressure, which will pull the boards straight apart, make sure there are enough screw holes placed into the receiving board. Shorter screws will easily suffer here when they have little grip.
Is A #8 Or 10 Screw Bigger?
When choosing a screw, the most important thing to remember is to be consistent. If you’re using galvanized joist hangers and post caps, you’ll also want to use galvanized screws. Corrosion and structural failure can happen from mixing and matching.
| "A" Flat Head | "A" Pan Head | "A" Round Washer Head | "B" Body Dia | "C" Thread Dia | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Max | Min | Max | Min | T max | Max | Min | T max | Max | Min | Max | Min | |
| 4 | 0.225 | 0.195 | 0.219 | 0.205 | 0.086 | N/A | N/A | N/A | 0.095 | 0.084 | 0.116 | 0.105 |
| 6 | 0.279 | 0.244 | 0.270 | 0.256 | 0.103 | N/A | N/A | N/A | 0.118 | 0.107 | 0.142 | 0.131 |
| 8 | 0.332 | 0.292 | 0.322 | 0.306 | 0.120 | 0.376 | 0.352 | 0.110 | 0.136 | 0.125 | 0.168 | 0.157 |
| 10 | 0.385 | 0.340 | 0.373 | 0.357 | 0.137 | 0.443 | 0.411 | 0.125 | 0.157 | 0.146 | 0.194 | 0.183 |
| 12 | 0.438 | 0.389 | 0.425 | 0.407 | 0.153 | N/A | N/A | N/A | 0.176 | 0.165 | 0.220 | 0.209 |
| 14 | 0.507 | 0.452 | 0.492 | 0.473 | 0.175 | N/A | N/A | N/A | 0.201 | 0.190 | 0.246 | 0.235 |
Pressure Treated Lumber
For pressure-treated wood, zinc-coated screws are the cheapest and most reliable option. However, the copper will eventually eat away at the zinc in modern pressure-treated wood.
Stainless steel screws in pressure-treated wood are a good investment. They won’t rust because they aren’t covered. Stainless steel is made of nickel and chromium combined with steel. Even if the cost is ten times more, it is still a bargain compared to the cost of decking.
Cedar
Cedar needs a dark decking build or stainless steel wood screw. Coated deck screws will bleed into the cedar and degrade the natural look. Stainless screws are not coated; therefore, there is no chance of wood discoloration. (Learn How To Remove A Rusted Screw)
Composite
Specific composite decking screws are specific for the material. For example, the star-shaped screw head includes a driver. In addition, they come with a small head to avoid material mushrooming, and a thick diameter offers excellent attaching strength.
What Size Is A #8 Deck Screw?
The deck screws and fasteners are crucial for holding the entire structure together. Consider the features and elements of deck screws, and how they affect the product’s quality, durability, and applicability.
| "A" Flat Head | "A" Pan Head | "A" Round Washer Head | "B" Body Dia | "C" Thread Dia |
|||
|---|---|---|---|---|---|---|---|
| Size | Max Dia | Max Dia | T max | Max Dia | T max | Min | Max |
| 4 | 7/32 | 7/32 | 3/32 | N/A | N/A | 3/32 | 1/8 |
| 6 | 9/32 | 17/64 | 7/64 | N/A | N/A | 1/8 | 9/64 |
| 8 | 21/64 | 21/64 | 1/8 | 3/8 | 7/64 | 9/64 | 11/64 |
| 10 | 25/64 | 3/8 | 9/64 | 7/16 | 1/8 | 5/32 | 3/16 |
| 12 | 7/16 | 27/64 | 5/32 | N/A | N/A | 11/64 | 7/32 |
| 14 | 1/2 | 31/64 | 11/64 | N/A | N/A | 13/64 | 1/4 |
Material and Coating
When looking for deck screws, take note of the material and if the screw has a weatherproof coating.
Due to their natural resistance to water and rust, stainless steel fasteners are ideal for light-colored deck boards.
Steel alloys and carbon steel can also be weatherproof to keep screws safe throughout lengthy winters and hot summers. The waterproof coating is essential for lakefront or seaside residences where the air is moist all year.
Head Style
Although flatheads are common on deck screws, there are various other types of screw heads to examine before deciding on the ideal format for your deck. Flathead, trim head, truss head, hex head, and round head screws are among them.
The screw head of a flathead screw is flat, and the flat head may lay level with the surface of the deck instead of sticking up.
- Trim head screws look like flathead screws but have considerably smaller heads. Because of the flat head and smaller diameter, these fasteners are suitable because of their holding power.
- Truss head screws feature an extra-wide screw head with a slightly rounded top that protrudes just above the surface to which they are fastened.
- Hex head screws have a hexagonal head with a built-in washer to spread the weight load over a larger area and improve holding power.
- Round head screws feature a flat screw head bottom and a rounded screw head top that protrudes from the screwed-in surface.
- Installing composite decking material onto your deck structure is usually done using a cap head or undercut screws. The screws include a larger head to help pierce the deck boards’ hard exterior capstock, as well as a reverse thread to avoid mushrooming.
Thread
The right screw thread can speed up a process, while the improper thread can halt it completely. The threads-per-inch measurement is usually found in the name or manufacturer’s information.
Deck screws usually have regular or coarse threads. While fine threads and a high thread count may work well in some woods, it is challenging to drive fine threads through pressure-treated deck boards because of the density of the wood fibers.
Length
Deck screws are typically 1 1/2 to 6 inches long, depending on the size of the two pieces of deck, joists, railings, and supports. The screw should fully penetrate one piece of wood or composite and about half of the length into the other to secure the two parts together.
A 6-inch screw would go through a 4×4 post and 2 inches into the deck’s framing or joists. Because they won’t protrude from the other side of the wood, 1-inch and 2-inch deck screws are suitable for anchoring ledger boards and joist hangers. (Read Can You Screw Into Concrete)
2 1/2 inch and 3-inch deck screws are ideal for railings, deck board, joists to ledger board, etc., while 6-inch deck screws are required for 4×4 posts.
#8 Or #10 Screws For Decking
When choosing the right deck screws, the size and type of decking materials, as well as the project’s location, must all be considered. Here are some specialized products and their situations of use.
Structural screws (lag screws) are thicker because they join load-bearing elements. Their strength makes them excellent for securing railing posts and attaching joists.
In the rain, sleet, or snow, non-coated stainless steel screws are good for light-colored wood.
In addition to having a smaller head and usually tighter threads, trim head screws help reduce composite tear-out.
Post and ledger board lag bolts and screws The head can be pressed into the lumber for a flush feel. Flathead screws can also be used here.
