The short answer
Those tiny holes just above your waistband aren't moths. They're friction holes: your belt buckle, jeans button or a countertop rubs the same spot every day until the yarn wears through. Every T-shirt gets them eventually, but merino gets them first, because its fine fibres wear through faster than cotton or polyester, especially in lightweight T-shirts. The fix is a heavier fabric or a reinforced yarn, and a little awareness of what you rub against.
Moths, washing or friction? How to tell
Where the holes are tells you what made them.
| Cause | Where you find the holes | What they look like | Fabrics affected |
|---|---|---|---|
| Friction | A band at the belly or waistline, sometimes the armpits or under a backpack strap | Small, round, often several in a row; broken yarn, fabric thinned around them | All fabrics, merino first |
| Moths | Anywhere, often hidden spots like the back or under the collar | Irregular; the yarn is eaten away rather than broken, sometimes with grazed patches or tiny larvae casings nearby | Wool, cashmere, silk; not cotton or polyester |
| Washing machine | Random spots | Snags or small tears | Fine knits washed with zips, hooks or Velcro |
If the holes line up at the same height on every tee you own, it's friction. If one tee that sat in a drawer all summer comes out full of holes, or you find holes in strange places, it's moths.
Why the holes always appear at your waistline
The waistline is where a thin T-shirt gets squeezed between your body and something hard. Every step, every time you sit down or lean forward, that spot is rubbed.
The usual suspects:
- the metal button and rivets on jeans
- a belt buckle
- a stiff denim waistband
- leaning against a kitchen counter, desk or sink
- a car seatbelt buckle
- a backpack hip belt
The knit doesn't fail all at once. Fibres break one by one at the surface until a single loop of yarn gives way. In a knit, a broken loop opens into a small round hole. So if you spend a lot of time in the car, pull your T-shirt out from under the seatbelt buckle. It's a small habit that makes your tee last noticeably longer.
Why merino T-shirts get holes faster
Merino is soft because its fibres are extremely fine, and fine fibres are fragile. Three things make a lightweight merino tee more vulnerable than a cotton one of the same weight:
- Fine, delicate fibres. Merino fibres are fine and soft, and they wear through faster than cotton or polyester under repeated rubbing.
- Thin yarns. A 150 gsm jersey is knitted from a fine yarn with relatively few fibres in its cross-section. Lose a few and the yarn snaps.
- No reinforcement. Pure merino has nothing in the yarn to hold it together once the surface fibres wear away.
That's why so many people love their first merino tee and are disappointed by month ten. It isn't bad luck or bad washing. It's the fabric.
Does a heavier merino T-shirt last longer?
Yes. Fabric weight, in grams per square metre (gsm), is the simplest indicator of strength when you compare two fabrics with the same composition. A heavier jersey has thicker yarns or a denser knit, so it takes longer to wear through.
| Fabric weight | Feel | Best for | Durability in 100% merino |
|---|---|---|---|
| 120 to 130 gsm | Very light, slightly sheer | Hot climates, layering | Fragile, holes can appear within months |
| 150 to 170 gsm | Classic T-shirt weight | Everyday, all seasons | Holes at friction points usually within a year |
| 190 to 200 gsm | Substantial, opaque | Cooler months, base layer | Noticeably sturdier, still wears at the waistline |
Heavier isn't a free fix: a 200 gsm tee is warmer and less airy in summer. Most people want a tee in the 150 to 190 gsm range, which is exactly where pure merino struggles. Our ClimaForce tees are 170 gsm, right in the middle of it.
100% merino vs core-spun vs spiral-reinforced yarn
Adding nylon helps, but how it's added matters as much as how much.
| Yarn | How it's built | Strength | Where it can still fail |
|---|---|---|---|
| 100% merino | Merino fibres twisted together | Lowest | Wears through at friction points |
| Intimate blend | Merino and synthetic fibres mixed before spinning | Better | Lower merino share means less odour resistance |
| Core-spun | Merino fibres wrapped around a nylon filament core | Strong in tension | The merino surface still abrades, exposing the core |
| Spiral-reinforced (ClimaForce) | A fine nylon filament spirals around a merino core like a coil, leaving the merino exposed between the turns | Highest in our tests | The filament takes the rubbing, protecting the merino underneath |
In a core-spun yarn the nylon sits inside, so it keeps the yarn from snapping but doesn't protect the surface. In a spiral-reinforced yarn the filament coils around the outside. It doesn't cover the merino, so most of what touches your skin is still wool, but the spiral takes the rubbing exactly where the belt buckle hits.
Why we developed our own yarn
For 16 years we've designed outdoor apparel for the biggest multibrand outdoor retailer in Europe and the UK. We worked with every kind of fabric, mostly synthetics with treatments to give them the right properties. In the high-end ranges we worked with merino, in different blends and from different suppliers.
As hikers, we became merino fans ourselves. We've crossed continents with nothing but a few merino tees. But one problem came back with every brand we wore, big names and small specialists alike: holes around the navel, usually within a year.
So when we started making our own merino T-shirts, that was the problem to solve. We tested dozens of off-the-shelf merino fabrics. We knitted samples with core-spun yarns. In the end we developed our own yarn, with a fine nylon filament spiralling around a merino core. We called it ClimaForce.
Lab tests showed we were on the right track: the fabric came out clearly stronger. But the real proof comes from years of real-life wear. Since we started in 2018, fewer than ten customers have come back to us with a hole. In several cases the hole wasn't in the typical spot and the yarn had been eaten away by moths. The others came from heavy backpack use, once combined with a belt with a metal prong buckle. What we hear far more often: "After five years, they still look like new." You can wear a merino T-shirt with ClimaForce for years without those holes at the navel.
Why we use 20% nylon, as material purists
If 100% merino performs to our standards, we use 100% merino. Our dress shirts are pure merino for that reason. But for T-shirts in the 160 to 190 gsm range, none of the pure merino fabrics we tested, and none of the pure merino tees from other brands, lasted longer than a year.
And even if they had, one year isn't enough. Not to justify the price, and not to justify using a precious natural fibre. A T-shirt that lasts years is the more sustainable choice, even with 20% nylon in it.
Does the nylon make it cheaper? No. We could buy cheaper 100% merino fabrics. That said, many standard blends, especially those with a lower merino share, are much cheaper than pure merino. So when you buy, check two things: the fabric weight and the merino percentage. The higher the merino share, the better the temperature regulation and odour resistance. With 20 to 30% nylon reinforcement you keep nearly all the merino benefits, and the tee lasts much longer. More on that in how to choose a merino wool T-shirt.
What even the toughest T-shirt can't handle
A reinforced yarn buys you years, not immunity. Some things wear through any lightweight jersey:
- a belt buckle pressed under a car seatbelt
- a backpack hip belt cinched tight on a long hike
- leaning or scraping against a countertop every day
- sharp hooks, Velcro and zips, in the wash or on your bag
Keep those in mind and your T-shirts will thank you.
