11/10/2025
You don’t hear this talked about much—at least not enough—and I’m surprised because it’s such a simple step that can save you a lot of headaches down the road. I’m talking about checking the moisture content in laminate before you go re-laminating. Whether it’s Facebook groups, YouTube tutorials, or boat repair forums, most folks just grind back the damaged area, assume the fiberglass is “dry enough,” and dive straight into glassing. But for me, that’s never been enough.
I’ve always taken what you might call a “belt and braces” approach with repairs—especially on boats. I don’t want to do the job twice, and the idea of a repair failing below the waterline? That’s a nightmare I’d rather avoid completely.
I’ve watched countless videos where nobody bothers to check moisture levels before laying new glass or replacing core material. Transom repairs done from the inside, for example—no check. Grinding out osmotic blisters one day and filling them the next—there’s just no way the laminate is dry enough in 24 hours, no matter how sunny it’s been.
Here’s the thing: where there’s been a wet core, the glass itself often stays wet too. Not just a little damp—you’re looking at moisture trapped deep inside the inner glass skins. I’ve removed rotten core material on my own boats more times than I can count, and even after scraping out every bit of decay, the laminate underneath often reads way off the charts on my Tramex Skipper marine moisture meter.
Simply waiting or using heat won’t fix it. The only way I get the moisture down to acceptable levels is by removing more laminate, cleaning that exposed surface thoroughly, letting it dry out naturally, then rechecking a few days later. Sometimes I have to repeat that routine several times before hitting the green zone on the meter.
And another thing most people don’t realise: the moisture in fiberglass isn’t always just water. It’s often this sticky, slightly acidic residue—sort of a vinegar smell—that comes from polyester breakdown. This residue holds moisture tight, making it really hard for the laminate to dry properly. That’s why I swear by steam cleaning; it washes out this contamination gently but effectively. If you’re working outdoors, even a pressure washer can do the trick.
I always use epoxy for repairs; it’s a bit more forgiving when it comes to moisture and still bonds well. But I still stick to the same rule—I want everything as dry as possible before I start glassing. Polyester? Now that’s a whole different story. Even a tiny bit of moisture can wreck the bond, causing delamination later on.
So, with my Tramex set to the GRP scale, I’m looking for readings comfortably in the green before I re-laminate—sometimes I try to get it even lower, but green is my safety net.
Maybe I go a little “over the top” compared to most, but honestly? I’d rather spend extra time upfront than rip out a failed repair a few months later. I’m not here to tell anyone how they should fix their boats—just sharing what works for me and why I keep coming back to this moisture check every single time.
