Understanding Fabric Curl and Railroading in Roller Shades

If you've ever noticed the edges of your roller window shades curling slightly, you're not alone—and it’s not a sign of a defect. In fact, this is a natural characteristic that can occur with many types of shade fabrics, especially when certain fabrication techniques are used. Let’s break down why this happens, what "railroading" means, and how to set expectations when selecting roller shade materials.

What is Fabric Curl?

Fabric curl refers to the subtle (or sometimes more noticeable) curling of a roller shade’s side edges. It’s most often seen when the fabric does not hang perfectly flat, and it may become more pronounced over time due to factors like:

• Tension and gravity over time

• Changes in humidity and temperature

• Inherent characteristics of the fabric weave or coating

• How the fabric was cut or oriented during manufacturing

While this can be more visible with some fabrics than others, it does not affect the overall performance or durability of the shade. Still, it’s something we like our customers to be aware of up front.

The Role of Railroading

"Railroading" is a common term in the window covering industry that refers to rotating the fabric’s orientation 90 degrees during fabrication. Instead of cutting the fabric vertically along the roll (which is the traditional method), the material is cut horizontally across the roll.

Why Railroad Fabric?

This method is typically used for a few reasons:

• To create wider shades without visible seams

• To align specific fabric patterns or textures in a certain direction

• To minimize waste when using a limited fabric width

While railroading is often a practical and aesthetic choice, it can slightly affect how the fabric behaves—particularly when it comes to curling.

Why Curl Is More Common With BO (Blackout) Fabrics

Blackout fabrics tend to be more rigid due to the multi-layer construction or added coatings that block light. When these fabrics are railroaded:

• The stiffer internal layers may respond differently to tension, especially when gravity pulls along the fabric’s cross-grain

• The non-woven or laminated layers can react to temperature/humidity fluctuations

• The curl can become more visible on the side edges, where the tension and structural integrity vary

This is exactly what Brad observed while in Portland, and it’s something we often explain to designers, installers, and customers to set clear expectations.

How to Minimize Curl

Although a small amount of curling is often unavoidable, there are some ways to reduce the visual impact:

• Choose lighter or softer fabrics when possible

• Avoid very wide shades if using a blackout fabric (or split them into multiple panels)

• Use side channels or guides in high-precision applications

• Allow for natural settling time after installation—some curling reduces after a few weeks

• Choose fabrics that are not railroaded, if curling is a major concern

We also work with vendors who test and pre-condition their fabrics to reduce curling effects during normal usage, but some factors will always come down to the physics of fabric behavior.

At Vanguard Specialty Products, we believe that an informed client is a satisfied client. That’s why we go beyond simply supplying high-quality shading solutions—we educate, guide, and collaborate at every step. From helping you understand fabric behavior like curling and railroading, to recommending the best materials and fabrication techniques for your project’s needs, our team brings technical expertise and a commitment to transparency. Whether you’re a designer, builder, or end user, we’re here to ensure your window coverings perform beautifully and meet expectations long after installation.