What Thread to Use for Outdoor Fabric

Thread is the cheapest thing in your build and the first thing that fails. Here is how we pick it, including the part most guides leave out.

We started ReFasten because sourcing this stuff in Canada was miserable. Thread is the category where that is still most true: finding the best thread to use on your outdoor projects is difficult. 

Polyester vs Nylon Thread

Nearly every thread on our shelf is 100% polyester, and that is not an accident. It has high tensile strength, very little stretch, and it holds up to UV and moisture. The low stretch matters more than people expect. A thread that gives under load lets the seam open before the thread itself breaks, so your stitch line goes slack at exactly the moment you need it tight.

Nylon has slightly higher breaking strength, which is why it keeps coming up when people search for heavy duty thread. It also stretches, and it degrades in sunlight. Both are disqualifying for gear that lives outside. 

PTFE is genuinely better than polyester for permanent outdoor exposure. Boat covers, awnings, anything sitting in salt and full sun for years. It is also expensive, slippery, holds knots poorly, and wants a well tuned machine. Unless you are sewing marine canvas, it is the wrong trade, and we would rather tell you that than sell you a cone you will fight with.

Continuous filament, core spun, bonded

Two threads can both be polyester and behave completely differently.

Continuous filament is twisted from long unbroken filaments. It is the strongest construction for a given thickness and its smooth surface shrugs off abrasion. Gütermann's TERA line is continuous filament, and it is what we recommend for gear. Core spun wraps short fibres around a filament core, which grips well and handles sewing heat better but gives up a little strength. Bonded is not a separate fiber at all, it is a resin coating that locks the twist so the thread will not fray through the needle eye. If your thread keeps shredding at the eye on heavy work, a bonded thread usually fixes it outright, before you start adjusting tension.

Reading Tex, and why the numbers look backwards

Tex is the weight in grams of 1,000 metres of thread. If 1,000 m weighs 40 g, it is Tex 40. Higher number, thicker thread. That is the entire system, and it is linear, so Tex 70 really is twice the mass per metre of Tex 35.

The confusing part is that Gütermann's own product numbers run the other way. TERA 40 is heavier than TERA 80. Same with MARA. 

If a listing anywhere gives you a ticket number instead of a Tex, ticket numbers also run inversely. Ask for the Tex.

Needles

We do not sell needles yet, so nothing in this section is us trying to sell you something. Schmetz packs are available at any sewing shop and most fabric stores, and a five pack costs a few dollars.

The needle is the step people skip, and it causes more problems than any other single choice. Its job is not only to pierce the fabric. It carries the thread through and opens a hole big enough for the thread to pass without friction. Too small and the thread abrades on every stitch until it snaps. Too large and you are punching holes bigger than the seam needs, which weakens light fabric and lets water through coated ones.

Needles carry two numbers printed together, like 90/14. The first is European, the second American. Same needle, two systems, and both go up as the needle gets thicker. Pick one and ignore the other. The sizes on the chart above are the ones to use.

Point type matters as much as size on our fabrics:

• Universal is the default and is fine for most wovens, Cordura and canvas.
• Microtex has a slim, acute point that makes the smallest, cleanest hole. Use it on anything coated or laminated: technical laminates, silpoly, X-Pac, Ultra.
• Denim has a reinforced blade that resists deflection through thick tightly woven material. Use it on canvas, 1000D and webbing stacks.
• Ballpoint pushes between knit loops rather than cutting them. Use it on mesh, stretch and fleece.

On waterproof laminates, a Microtex needle plus a slightly longer stitch is the single best thing you can do for seam integrity. You are perforating a membrane on every stitch, so fewer and smaller holes beats more and larger ones.

Will your machine actually sew this?

This is the question we get most, and it is the one that stops people from moving up in thread weight. The honest answer is that it depends on the machine, but the ranges are predictable.

Most modern domestic machines are comfortable up to about Tex 45. Many will run Tex 70 in the needle with something lighter in the bobbin, fitted with a 100 or 110 needle and the top tension increased to compensate. Past Tex 70 you are generally into walking foot or industrial territory, because the take up lever, tension discs and bobbin case were not built for the bulk.

Older all metal domestics are a different story, because the drive train has the torque and the parts have the mass.

Signs you have pushed past what your machine wants: skipped stitches that appear only on thick sections, a nest of thread building underneath, the motor bogging through seam intersections, or top thread breaking every few inches no matter what you do to the tension.

If you see those, drop one weight before you start taking anything apart. Heavier thread is not the only route to strong gear. A well placed box stitch in Tex 45 will outperform a badly formed straight stitch in Tex 70 every time.

Pairing thread to our fabrics

How much thread a build actually uses

More than you'd think. A lockstitch pulls from the needle and the bobbin and loops around itself at every stitch, so you burn about three times your seam length.

The garment industry plans at 2.5x. We round up, because pack seams are thicker than shirt seams and ply count is the thing that really drives consumption. A strap anchor is webbing over binding over face fabric over reinforcement. That eats thread.

Add up the seams on your pattern, multiply by three, add ten percent for the bits you unpick.

Which means a 400 m TERA 40 cone is about 130 m of finished seam. A 6,000 m Poly Plus 40 cone is closer to 2,000 m.

What your stitches are telling you

Common questions

Where to start

If you are new to this and want one thread that handles most of what you will build, get MARA 70 in a colour you like, or Poly Plus 40 if you would rather have 6,000 metres for the same money and can live with a cone stand.

If you are already building and want to stop thinking about thread cost, buy a Tex 70 and a Tex 45 deadstock cone and you are set for years.

Not sure which pairing suits your build? Send us the fabric and the project and we will tell you what we would use. Browse all thread or start with the fabric.