Lining, Underlining and Interlining Explained! How to Add Structure + Warmth to Your Sewing Projects

Lining, underlining, interlining, interfacing… these words can often blend together in a confusing cacophony of sewing phrases. But what do they actually mean? How do you know which construction method to use in your sewing project? We recently published an in-depth blog on interfacing and today we’ll explain the differences between underlining, interlining, and underlining, and how and when you should be using them to construct garments.

What is a Lining?

A lining is a second layer of fabric inside a garment. A lining serves a few purposes. First, it creates a smooth layer that helps garments lay smoothly against the body. When sewn in a silky fabric like bemberg or silk, they make it easier to slide jackets and coats over other clothing. Second, they also serve to hide the construction of the garment so you don't see or feel the seams when wearing it. Linings are generally assembled separately to the outer layer of the garment and are then stitched together at a neckline, waistband or facing to secure together. They generally don't serve to add structure to the garment.

Types of Lining Fabrics

Generally, when lining a garment you want to choose something lightweight with a smooth face so it easily glides easily over your body and other clothes. Here are our top picks:

• Bemberg is a type of rayon fabric with a smooth, silky face. We carry a variety of colours of Bemberg cupro which is made entirely of cotton textile waste! Lightweight and super breathable, its a budget friendly and sustainable lining option.
• Silk is a luxurious choice for lining fabrics, especially a smooth silk charmeuse. 
• Lightweight and finely woven cottons like batiste, sateen and poplin also work well as linings for more casual garments.

What is Underlining?

Underlining is a sewing technique that adds structure and/or weight to your sewing projects. Essentially, it involves cutting a second layer of your pattern pieces using a different fabric. Unlike fusible interfacing, underlining is sewn to all of your pattern pieces near the seam allowance. These two layers are then sewn as if they are one single piece of fabric. 

Why Underline Your Garment?

Underlining is often used in tailored and couture garments, and learning to underline properly can take your sewing projects to a whole new level.

First, underlining can help add body structure to fabric. For example, if you're making a sharply tailored blazer with a softer fabric like boucle, underlining with a fine cotton muslin can help give the boucle a crisper hand and hold a more defined shape. In formalwear, it's often used for structural reasons, and provides a way to secure or hide elements like bonining and stays. It also provides a place for any hand-stitches to be safely secured out of sight. Translucent fabrics can be underlined to add depth to their visual appearance; try underlining lace or eyelet fabric with a contrasting solid to produce a bold look. 

Want to learn more about how to undlerline your garments? Visit this helpful blog post from our sister brand Closet Core Patterns!

Types of Underlining Fabrics

You can underline with a variety of fabrics, depending on the purpose and designed outcome. As with interfacing, you don’t want to underline your project with anything significantly heavier than your main fabric, as the goal is not to weigh your garment down, but to support it!  

• Cotton Muslin is ideal for for hiding hand stitches, boning, and other construction element. Choose a similar weight to your main fabric in order to provide enough structure while not overpowering it.
• Silk organza adds volume and body without additional weight. Organza is stiff enough to bulk up drapey fashion fabrics, but delicate enough to maintain an elegant final look.
• Plain-woven cottons such as cotton batiste work as an all-purpose underlining material. Batiste provides stability while allowing for movement and breathability. 

What is Interlining?

An interlining is similar to an underlining in that it is a second layer of fabric cut from your pattern pieces and then treated as one. However, an interlining is created primarily to add warmth to a garment. It is generally sewn to the main fashion fabric just inside the seam allowance, and then trimmed or graded to reduce bulk.

Types of Interlining Fabrics

The most important consideration with choosing an interlining is the degree of warmth you are after and the type of garment you're interlining. 

• Cotton flannel adds a lightweight yet cozy layer to cold weather garments. If the garment is not lined, the brushed face of flannel is soft against your skin - think about how great a flannel interlined trouser would feel in the dead of winter! Flannel works great for lighter weight garments like trousers and dresses, but will add a small degree of warmth to heavier jackets and coats as well.
• Quilt batting in cotton, bamboo, and wool blends makes a lovely and warm interlining for cozy winter coats. And best of all, they will biodegrade over time!
• Performance interlinings like Thinsulate can also add a great degree of warmth and are typically used in ready to wear. However, they are typically made from virgin polyester and nylon; for a more sustainable option, we recommend our recycled silk and wool interlining!

Want to learn more about how to interline for warmth? Visit this helpful blog post on how to interline a coat from our sister brand Closet Core Patterns!

Hopefully this clears up any confusion out there about these helpful sewing techniques, and we would love to hear about your favourite interlining and underlining fabrics!