What is Interlining?

Interlining is an additional layer of material placed between the outer fabric of a garment and its lining. It can be used to add warmth, structure, body, stability or other performance characteristics without being visible in the finished garment.

Different types of interlining are used for different purposes. Some provide insulation in coats and jackets, while structural materials can help garments maintain their shape.

Where does interlining sit in a garment?

An interlining sits inside the construction of the garment, between the outer fabric and the inner lining.

A simple way to picture the layers is:

OUTER FABRIC → INTERLINING → LINING → BODY

The outer fabric provides the visible exterior.

The interlining provides additional structure, warmth or performance.

The lining creates the finished internal surface that sits against the wearer or their clothing.

Because the interlining is sandwiched between these layers, it generally isn't visible once the garment is finished.

What does interlining do?

The purpose depends on the garment.

An interlining may be added to provide:

Warmth – insulating materials can be placed between the outer fabric and lining of coats and jackets.

Structure – an additional layer can give lightweight fabric more body.

Stability – it can help particular areas maintain their intended shape.

Support – structured garments may require internal materials to support their silhouette.

Performance – specialised internal layers can provide additional properties depending on the garment's intended use.

Is interlining the same as lining?

No.

Lining is the finished layer covering the inside of a garment. When you open a lined blazer, the smooth fabric you see is the lining.

Interlining sits between that lining and the outer fabric and normally remains hidden.

So:

Outer fabric → what everyone sees

Interlining → hidden middle layer

Lining → what you see inside

Is interlining the same as interfacing?

Not quite, although terminology can vary somewhat within the textile and clothing industries.

Interfacing is generally a material used to reinforce or stabilise specific areas of a garment.

It's commonly found in:

• collars
• cuffs
• waistbands
• button plackets
• lapels
• pocket openings

Interlining more broadly describes an additional layer incorporated between the outer fabric and lining.

What is fusible interfacing?

Fusible interfacing has an adhesive on one surface. Heat and pressure are used to bond it to the reverse of the garment fabric.

Once fused, it helps stabilise and reinforce that area.

It's widely used in modern clothing production because it can provide consistent structure without requiring the supporting material to be extensively stitched into place.

What is sew-in interfacing?

Not all structural materials are fused.

Sew-in interfacing is attached through the garment's construction rather than bonded to the outer fabric using adhesive.

The appropriate method depends on the fabric, garment design, desired result and manufacturing technique.

What is insulating interlining?

In coats and outerwear, interlining can be used specifically to provide thermal insulation.

An insulating layer might sit between the exterior shell and the garment's lining.

Depending on the garment, this could include materials such as:

• quilted insulation
• fleece
• wool
• synthetic insulation
• other thermal materials

This allows the visible outer fabric and comfortable inner lining to perform different jobs while the hidden layer provides additional warmth.

Is interlining always fused to the fabric?

No. Some internal structural materials are fusible, meaning heat and pressure activate an adhesive that bonds the material to another fabric.

Others are sewn, quilted or otherwise incorporated into the garment construction.

Whether an internal layer is fused therefore depends on what material it is and what job it's performing.

Why are collars and cuffs reinforced?

Collars and cuffs need to maintain their shape despite repeated movement and wear.

Without additional support, some fabrics would be too soft to produce the crisp, structured appearance required.

Interfacing can therefore be placed inside these components to add body, stability and shape.

A classic business shirt collar is an excellent example.

The cotton or polyester/cotton fabric you see on the outside isn't necessarily responsible for all that structure. There's some hidden engineering going on inside.

Why are waistbands reinforced?

Waistbands are another area that often benefits from interfacing.

They need to maintain their shape while coping with movement and tension during wear.

An internal stabilising layer can help prevent the waistband from becoming excessively soft, stretching out of shape or collapsing.

Again, this is more accurately described as interfacing than interlining.

Interlining vs interfacing vs lining

Does every garment have interlining?

No. Many garments don't need it at all.

A simple T-shirt, polo or lightweight casual shirt might consist primarily of the garment fabric itself.

More complex tailored and outerwear garments can contain several different layers and structural components.

Whether interlining is required depends on the fabric, garment construction, desired silhouette and intended performance.

Interlining in uniforms

Interlining and interfacing are particularly relevant in tailored corporate uniforms and outerwear.

Corporate jackets may contain hidden structural materials that help create their shape.

Business shirts may use interfacing through the collar, cuffs and button placket.

Winter jackets and coats can contain insulating layers between their exterior fabric and lining.

These components aren't particularly obvious when you're looking at a finished uniform, but they can make a substantial difference to its appearance, structure, comfort and performance.