The Hidden Damage Beneath the Screw: Why Deck Fasteners Deserve More Respect
Don’t Just Screw it in: The Right Way to Fasten Hardware to Your Deck
The Hidden Problem Beneath the Screw
Every season, I find it—the innocent little screw that opened the floodgates. A cleat, a rod holder, or a deck fitting installed with good intentions but no understanding of what lies beneath. Most yacht decks aren’t solid fiberglass; they’re sandwiches of fiberglass skins and a lightweight core that gives stiffness without weight. Drive a screw straight into that core and you’ve just created a hidden pathway for water, rot, and structural failure. What looks secure today can quietly destroy a boat from the inside out.
How Proper Fastening Protects Your Deck
To prevent that slow-motion damage, every deck fastener should be treated like a potential leak waiting to happen. Proper installation starts with understanding what you’re fastening into. The correct method—recommended by ABYC and most builders—involves drilling an oversized hole, removing a small ring of core around it, and filling that cavity with thickened epoxy before re-drilling a pilot hole for the fastener. This creates a solid, waterproof plug that isolates the screw from the core. Finally, bedding the hardware in a marine sealant ensures a watertight seal at the surface. It’s a few extra steps, but they turn a vulnerable screw into a permanent, dry, and structurally sound connection.
Some Framework for Thought
When installing or replacing deck hardware, a few key steps can save you years of trouble down the line. These are the methods I rely on in the field, and they’ve proven to stand up to both time and the elements:
Know Your Deck Composition.
Before drilling, confirm whether the deck is cored (and with what material). Balsa, foam, and plywood each require slightly different sealing approaches.
Drill Oversize.
Create an opening slightly larger than the fastener’s diameter to expose the core. This ensures you can properly seal it.
Isolate the Core.
Remove a small ring of core material around the inside of the hole using a bent nail, Dremel bit or pick. This creates a cavity for sealing.
Fill with Thickened Epoxy.
Mix epoxy with a filler (such as colloidal silica) and inject it into the cavity. Once cured, you’ve got a waterproof “plug” that securely holds fasteners
Re-drill the Pilot Hole.
Drill your fastener hole through the solid epoxy plug-never through bare core.
Bed the Fitting.
Use a high-quality marine sealant (such as a polysulfide or polyurethane) under the hardware to prevent water ingress at the surfaces.
Tighten by Feel.
Don’t over-tighten. Compress the bedding just enough to form a watertight seal without squeezing all the sealant out.
Note: These steps may seem tedious, but they turn a potential weak point into one of the strongest parts of the deck. It’s the kind of detail that separates a boat that stays solid for decades from one that’s headed for a core-repair estimate.
Stay Ahead of the Damage
As a marine surveyor, I see the aftermath of shortcuts like this far too often—soft decks, hidden moisture, and expensive core repairs that could have been avoided with ten extra minutes of care. The good news is that this is one of the easiest problems to prevent. If you’re mounting new hardware or replacing old fittings, take the time to isolate the core and seal every penetration properly. It’s a small investment that protects your deck, preserves your boat’s value, and keeps you focused on the water instead of the repair yard.
If you’d like to learn more about proper installation practices—or have concerns about water intrusion or soft spots aboard your vessel—feel free to reach out through DaTroyMarineSurveying.com. I’m always happy to help boat owners protect their investment before small issues become costly repairs.
Lastly, I came across a great video and photo series from Sailing Hiraeth that really drives this point home. It walks through each step of proper deck fastening and shows exactly why the extra effort matters. If you’ve never seen this process done correctly, it’s worth a few minutes of your time.
