How To Select Interfacing Weights for Sewing Projects

Choosing the right interfacing can make or break a sewing project, providing essential structure while maintaining the fabric's natural drape. This guide explores when to use lightweight, medium, and heavyweight interfacing across different fabrics and applications. A handy table matching different fabrics with appropriate weights of interfacing in included to help dressmakers and sewists achieve professional results.

Understanding Interfacing and Fabric Weights

Fabrics Galore's Interfacing Fabric Collection

Interfacing adds body, structure, and reinforcement to fabrics, so selecting the appropriate weight is crucial for success. A fundamental rule when choosing interfacing is to select one with a similar or lighter weight than your fabric.  Fabric weights are typically measured in GSM (grams per square metre) as you will see on nearly all the Fabrics Galore product descriptions:

• Lightweight fabrics: 30-150 gsm (e.g., cotton lawn, double gauze, linen, sateen, viscose, voile)
• Medium weight fabrics: 150-350 gsm (e.g., jersey, velvet,  fleece)
• Heavyweight fabrics: 350+ gsm (e.g., upholstery fabric, canvas, denim, wool)

Understanding these classifications helps match appropriate interfacing weights to your specific fabric.

A table of Fabrics Galore key fabric types and the appropriate interfacing weight is provided further below. All our interfacing is premium cotton interfacing, rather than paper interfacing.

Lightweight Interfacing

Suitable Fabrics and Applications

Lightweight interfacing provides subtle support without adding bulk, making it ideal for:

• Delicate fabrics including silk, viscose, acetate satin and cupro.
• Sheer and lightweight materials like voile.
• Small parts of less structured garments such as collars, cuffs, and facings.
• Fine blouses and shirts requiring minimal structure and support.

Our lightweight cotton iron on (fusible) interfacing is available in white and black and at 55 gsm is perfect for maintaining the natural drape of delicate fabrics.

Special Considerations

When working with lightweight interfacing:

• Apply with a cool iron to prevent damage to delicate fabrics.

Medium-Weight Interfacing

Suitable Fabrics and Applications

Medium-weight interfacing provides more substantial structure while maintaining flexibility:

• For example, Quilting Cotton, ponte roma and medium-weight wools.
• Structured shirts, dresses, and tailored garments.
• Waistbands and facings in skirts and trousers.
• Projects requiring moderate structure and support.
  
  

Our medium weight cotton iron on (fusible) interfacing is available in white and black and at 102 gsm it maintains the structure of less drapey garments made from medium weight fabrics with a gsm of 150 - 350.

Special Considerations

For medium-weight applications:

• For cotton fabrics that tend to crease, woven interfacing may be preferable to non-woven varieties.
• Medium-weight interfacing offers versatility across a wide range of projects.
• Provides good stability in structured garment areas without excessive stiffness.

Heavyweight Interfacing

Suitable Fabrics and Applications

Heavyweight interfacing delivers firm support and rigid structure, ideal for:

• Canvas, heavy denim, and upholstery fabrics.
• Bag panels, bases, flaps, handles, and straps.
• Structured coats, jackets, and tailored outerwear.
• Projects requiring significant stability and shape retention.
  
  

Heavy weight woven fusible interfacing is ideal for reinforcing bags (panels, flaps and handles or straps), and retains the shape of your make without making your project too bulky.  It's designed to work with medium and heavy weight fabrics such as canvas, heavier weight denims, faux leather, and heavyweight wools.

Special Considerations

When working with heavyweight interfacing:

• Fuse without steam using a pressing cloth for protection.
• Press for 8-10 seconds without moving the iron to prevent stretching.
• Allow fused pieces to cool completely before handling to ensure proper bonding.
• Test on fabric scraps before applying to your project.

Specialised Interfacing Types

Interfacing for Stretch and Knit Fabrics

Standard interfacing can restrict the natural stretch of knit fabrics. For these materials:

• Stretch interfacing is designed specifically for knit and Jersey fabrics.
• Knit interfacing stretches with the fabric, preserving comfort and fit.

Table of Fabrics with Suitable Interfacing Weights

Select the Correct Interfacing for your Sewing Project

Use the handy table above as a guide but if you are unsure of the weight of your fabric, and which interfacing is needed, don't hesitate to call the expert team at our Fabrics Galore shop in London on 020 7738 9589.

Authored by:  Annabelle Rigg, Online and Store Manager at Fabrics Galore London

Reviewed by: Paul Johnston, Owner and Founder of Fabrics Galore London since 1992