Best Deck Screws for Treated Decking
Deck screws do one job, holding a board down flat, and they do it outdoors for twenty years while sitting in lumber that actively attacks metal. Everything worth knowing about choosing them comes down to the coating, the drive, and the length.
Coating first, everything else second
Modern pressure treated lumber is saturated with copper based preservative, and it corrodes ordinary steel fasteners fast. A deck screw with the wrong coating will be the first thing on your deck to fail, usually with rust streaks down the boards within a couple of seasons.
| Coating | Rated for | What you see |
|---|---|---|
| Epoxy or polymer coated (bronze, tan, brown) | Treated lumber, general exterior | The standard deck screw. Coloured to disappear into the wood |
| Ceramic or multi-layer coated | Treated lumber, higher end | More expensive, longer life, better holding the color |
| Hot-dip galvanized | Ground contact and heavy exposure | Thick and rough, silvery gray. Reliable and cheap |
| Stainless steel | Coastal, and cedar or redwood | The only fastener that will not react with cedar tannins |
The general rule: match the coating rating to the lumber rating. Screws sold as rated for treated lumber are the cheap insurance here.
Drive type: this decides whether the job is pleasant
- Star / Torx (usually T25). The bit seats deep and does not cam out. You can drive one-handed, overhead, or at an angle, and the bit lasts a whole deck. This is what to buy.
- Square drive. Almost as good, common on older and budget screws, and fine if you have the bits.
- Phillips. Cam out constantly under the torque deck screws need, especially near a board end. Avoid it. You will be swearing by the third board.
Whatever you buy, check that the box includes the bit, or buy a handful of quality bits. A worn bit ruins screws and wrists at the same rate.
Head type
- Trim or star head. A small head with cutting flutes underneath that clears wood as it sinks, leaving a clean countersink with very little tear-out. Best looking result on visible decking.
- Bugle or flat head. The general purpose head. Self-countersinks reasonably well on softwood and is cheaper.
- Pan or washer head. Sits proud of the surface. Used with hidden fastener clips and on some composite systems, not for face screwing boards.
Length and diameter
Length is decided by the board you are screwing through plus the bite you want in the joist. The working target is at least 1-1/2 inch of thread into the joist, which is why the two standard lengths cover almost everything.
| Decking | Thickness | Screw length |
|---|---|---|
| 5/4 decking | About 1 inch | 2-1/2 inch |
| 2x decking | 1-1/2 inch | 3 inch |
| Double 5/4 or thick board | 2 inch plus | 3-1/2 inch or longer |
On diameter, #8 is lighter and less likely to split board ends; #10 is heavier and holds harder, and it is the usual choice for 2x decking. Both are common and both work, as long as the coating is right.
What not to use
- Drywall screws. They are hardened and brittle, they snap under the movement a deck board makes, and they rust immediately outdoors. There is no version of this that works.
- Interior wood screws. No corrosion rating, no business on a deck.
- Ring or spiral shank nails for face fastening. They work for some decking systems but they pop up over time. Screws are the safer call for face fastening.
Fastening technique
- Two screws per joist crossing on standard width boards, roughly 3/4 inch in from each edge, and staggered slightly so they do not line up with the grain.
- Pre-drill near board ends. The last inch of a deck board splits easily, especially kiln dried material. A small pilot hole solves it.
- Do not overdrive. A screw driven too deep breaks the surface fibers and leaves a dimple that collects water. Stop when the head is flush.
- Leave the movement gap. Screws hold boards down; the gap between them is what lets the deck dry. Our deck board spacing chart gives the gap by board width and moisture.
For composite and PVC decking, use the fastener the manufacturer specifies. Many composites require a specific screw design, and face screwing some of them voids the warranty in favor of a hidden clip system.
Frequently asked questions
What length deck screw for 5/4 decking?
2-1/2 inch. That puts about 1-1/2 inch of thread into the joist below the 1 inch thick board, which is the bite you want without the screw punching out the bottom of the joist.
Do I need stainless steel screws?
Only in two situations: coastal salt exposure, and cedar or redwood decking, where the tannins in the wood react with ordinary steel and leave black streaks. For treated pine or fir inland, a good coated screw is the better value.
Can I use the same screws for the frame?
No. Framing connections carry the structure and need fasteners sold with structural load values. Deck screws hold deck boards. Our guide to structural framing screws covers the difference.
Why do my screws snap?
Usually one of three things: the screws are not rated for outdoor use and have embrittled, they are driven without a pilot hole into the end of a board, or the drive type is stripping and you are forcing it. Switch to a coated Torx drive screw and pre-drill the ends.
Recommended for this project
These are the current best-rated options on Amazon. Ratings and review counts are live, so check the listing before you buy.