Is it normal for deck screws to shear after just one season?

Impact drivers are definitely the primary culprit here, even though everyone uses them for decking. Those micro-strikes from the impact mechanism create tiny stress fractures in the shank that you can't see with the naked eye. When your deck boards go through a heavy wet-dry cycle, the lateral pressure from the wood expanding is immense. Since the screw has already been weakened by the torque pulses of the impact driver, it just snaps instead of flexing.

I stopped using GripRite years ago for exactly this reason. Their metallurgy seems way more brittle than high-end alternatives. If you're seeing corrosion already, the coating was likely compromised during the install or it's just a poor quality batch. You shouldn't see any rust in six months if the galvanization or ceramic coating is actually doing its job. Switching to **GRK R4** or **Simpson Strong-Tie** screws is the move. They're made from a higher grade of steel that has actual shear strength, meaning they can bend slightly as the wood moves without snapping off.

When you go back through with the new hardware, definitely switch to a standard drill with a clutch setting. It feels slower, but it prevents that over-torquing that kills the screw's integrity. Also, make sure you aren't over-driving the heads. If you bury the head too deep, you're creating a pocket for water to sit, which accelerates the corrosion on the top of the shank where the most stress occurs.

Since you're already pre-drilling the boards, you're halfway there. Just ensure your pilot hole is slightly larger than the shank of the screw. You want the board to be able to 'float' slightly around the screw so that when the wood swells, the board moves and the screw stays put. If the hole is too tight, the board grips the screw and uses it like a lever to snap the head right off. It's a massive pain to redo 1,600 screws, but staying with those brittle fasteners is just asking for a structural failure down the road.

I had the same nightmare with GripRite on a 20x15 pressure-treated build three years ago. Halfway through the first winter, I was finding heads on the grass every time it thawed. I swapped to 305 stainless steel screws and haven't seen a single snap since. In my experience, if you're using the newer ACQ pressure-treated lumber, it eats those cheap ceramic coatings for breakfast. If that coating gets even a tiny scratch during install, the chemicals in the wood rot the metal shank in months. The extra cost for stainless is brutal upfront, but it’s the only thing that actually stops the shearing for me.

Spot on about the brittle steel. One thing I’ve noticed people forget to check is the length of the smooth part of the shank. If your screw is threaded all the way up into the deck board, it locks the board and joist togather too tightly.

You relly want that smooth upper section to be at least as thick as your decking so the threads only grab the joist. This lets the board "slide" slightly along the shank as it expands instead of putting all that sideways force directly on the threads, wich is ussually where those GripRites tend to pop.

GripRite is hobbyist tier at best. If you’re driving 1,600 fasteners, you shold’ve been looking at the Spax #10 HCR or the GRK R4s. Most people grab #8 gauge screws at the big box stores, but they simply don't have the cross-sectional area to fight back when a wet pressure-treated board starts to cup. I’ve seen those cheap ceramic coatings flake off during the drive, leaving raw steel exposed to the ACQ chemicals. Switch to a #10 gauge. You need that extra thickness in the shank to resist the lateral shear that snaps those brittle #8s every time.