| Decking materials and fasteners. |
You’ve decided to build a deck? Great! Now you need to decide what material to use for the decking — the part you actually walk on. This decision is slightly more involved than it used to be. Some materials now available promise “near-lifetime” durability — good news if you don’t build decks for a living.
For your convenience, we have assembled a list of decking screws used for various decking materials.
Pressure-Treated Southern Yellow Pine has been the standard deck-building material for years. Even if you choose some other material for the decking surface, it is likely you will use pressure-treated pine for the structural members. It is relatively inexpensive, readily available in a wide range of sizes, and takes fasteners easily. On the down side, it is prone to checking, splintering, cupping, and twisting, has cosmetic defects such as knots and “wany” edges, and requires frequent surface treatment to avoid deterioration. Read here to learn more about ACQ and how it applies to the use of fasteners in Pressure Treated lumber.
Western Red Cedar and Redwood both produce beautiful decking, and are frequently specified for high-end custom decks since they resist splintering, cupping, twisting, and checking. However, they are rather soft, making wear a problem in high-traffic areas. In addition, the best “vertical grain” material is in short supply since it is cut from trees taken from old growth forests. Tannic acid in both sometimes reacts with galvanized fasteners to cause staining, so stainless fasteners are preferred. Predrilling is usually not required except near the ends.
Composite Polymer Wood (Trex®, Boardwalk®, TimberTech®, and Fiberon® are examples) is a relatively new material which is manufactured from recycled plastic and wood fiber. It is becoming readily available, and is manufactured in a variety of colors in both 5/4 and 2x thicknesses. The “weathered” color is often quite different from the unweathered color, though, so check color charts carefully. It does not have a perceptible grain, nor does it splinter, absorb water, or rot. It is also dimensionally consistent, and available in a wide range of lengths. In our testing, it took fasteners easily, but screws raised a small ring around the head. This can be an advantage, since the crater can then be pounded down, covering over the screw head, making them nearly invisible. You may also use our new Double-Dekker™ composite wood screw for a clean install when an exposed screw head is acceptable.
Tropical Hardwoods such as Ipe, Teak, Pau Lope®, or greenheart, are premium materials for long-life decks. The woods are very dense, and resist rot, cupping, splintering, twisting, and checking. However, they are generally only available on a special order basis. Based on their up-front costs, it is probably best to use stainless steel fasteners for longest deck life. Oversize clearance holes equal to the outside diameter of the threads should be drilled in the decking to avoid thread engagement except with the joist. Organizations distributing these materials often claim to obtain them from managed forests. Please check carefully before you buy!
How Many Screws?
Take the guess work out of selecting the type and quantity of fasteners you need for your decking project by using our Deck Calculator
Most of the fasteners needed for a deck are used to attach the decking itself. Use this table for any decking material, and either nails or screws. Quantities are for 100 sq ft of deck surface applied perpendicular to the joists. Diagonal or parquet patterns, deck railing, stairs, and benches require additional fasteners!
Fasteners Required per 100 sq. ft. of Deck
|2 x 4
|5/4 x 4
|2 x 6
|5/4 x 6
Which Screw Should I Use?
Selecting the best fastener for any decking job requires answering just three easy questions:
- What decking material will be used?
- Will the deck be exposed to a corrosive environment?
- How thick is the decking material?
The choice of fastener material is dictated by both the decking material and the environment. Galvanized screws work well with Pressure-treated decking, while Redwood or Western Red Cedar decks are usually built with stainless steel screws to prevent staining around the screw heads. The new man-made decking materials such as Trex® polymer wood can be fastened with either galvanized steel, ceramic coated, or stainless steel screws. Tropical wood decking such as Ipe, Pau Lope®, or Teak is generally fastened with stainless steel screws for virtually a lifetime of maintenance-free service. The corrosive atmosphere of a seaside location dictates a minimum of Type 305 stainless steel fasteners regardless of the decking material used. Docks, because of their more severe service requirements, should be built with Type 316 stainless steel screws.
See Screw Sizes
Screw material also dictates the screw gauge required. Our coated, hardened steel NoCoRode PLUS screws are strong enough that #8s are adequate for most applications, while the softer Stainless Steel normally requires a #10 screw. If you are in an area experiencing extreme weather conditions, or the structure may experience unusual loads, consult a Licensed Professional Engineer for design assistance.
What Type of Head?
In most applications, Flat heads are the best choice for fastening decking boards. Generally, we do not recommend using trim heads for decking. Trim head #7 stainless can be too soft for installation without predrilling (remember, we recommend #10 for stainless!) and the smaller head size can pull through softer materials. However, there are some exceptions: The Head Coat Trim head screws (or reduced heads, as they are somewhat larger than traditional Trim heads) are fine for use with hard exotics such as Ipe IF you predrill. HeadCote offers a SmartBit Countersink that is perfect for this use. Some composite manufacturers will specify Trim heads, but be sure to check your specific material’s installation recommendations. Composite Screws such as our Double-Dekkers™ offer a specialized thread and head that tucks in and caps the exhaust material. This prevents the mushrooming effect common when using standard screws with composites.
See Screw Lengths
Fastener length is easiest to determine, since it is governed by the thickness of the decking itself. For securely fastening decking boards, we recommend choosing a screw length that will offer approximately 1-1/2" embedment into the secondary material.
Standard 2 x 4s or 6s require a 3" long fastener (2-7/8" for ProMax®) , while 5/4 x 4s or 6s only require a 2-1/2" long fastener (2-3/8" for ProMax®). Our ProMax® Line of screws offer thread lengths that are optimized to prevent jacking when used with specifically dimensioned materials. They are also 1/8" shorter than standard screws. The 2-3/8" is equivalent to 2-1/2" while the 2-7/8" is equivalent to a 3" screw. There will no significant reduction in holding power.
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