The Importance of Inner Structure Part 1

Fabric is a fluid medium.  It will move and drape according to its thickness and weight.

The outer appearance of any garment is greatly affected by the care taken to provide the correct inner structure for the fabric and style of the garment.

There are many choices to be made.  Hopefully, this information will help in evaluating the desired effect for each garment and in making your decision on what will work best for your project.


  • Interfacing is the most commonly used method of providing support to the outer edges of a garment
  • The purpose of interfacing to support the style and enable the garment to keep its shape during wear, increasing its longevity and resilience during and after wear
  • Always found in applied neckline and armhole facings and as otherwise indicated in the guide sheet but its use can be extended to other areas of the garment
  • Interfacing fall into two groups – fusible and non-fusible
  • Both groups also can also be either woven or knit fabric types and both types have fabric grain which needs to be used in a similar way to the fashion fabric
  • Most commonly, fusible interfacings are used and they come in different weights to suit different fabrics and garment styles
  • If a fabric is not suitable for fusible interfacing, the sew-in variety is used instead – cotton, organza, hair canvas – all of which can be either on the straight of grain or bias which results in a more fluid drape
  • Either type of interfacing is cut from the appropriate pattern pieces and either fused to the wrong side of the fabric or hand tacked to the wrong side of the fabric
  • When using sew in interfacing:
    • Cut interfacing on the same grain as the fashion fabric and slightly smaller than each pattern piece being used
    • Place the interfacing on the wrong side of the fashion fabric and hand tack close to the seam line, just within the seam allowance
    • Once seams are sewn or edges taped, cut excess interfacing away from within the seam allowance
    • Cut out shape of darts to avoid build up of excess in the dart stitching line – darts are usually slashed open and attached to the interfacing by hand using a catch stitch
    • Pad stitch to attach the interfacing to the fabric – heavier padstitching can be used to add extra stiffness where required (see blog post 21st June, 2015)
  • To achieve the correct adhesion of fusible interfacing, you need to:
    • Warm up the fabric by ironing the wrong side of the garment piece to be interfaced
    • Place the glue (rough) side of the interfacing on the wrong side of the fabric
    • Cover with a press cloth
    • Using a steam iron and a lift and press motion, move over the piece leaving the iron in place for 10 seconds each time – also press firmly on the iron to ensure it fuses properlyIf you do not have a good steam iron, use a spray bottle to moisten (not wet) the press cloth and press until the cloth is dry
    • Turn the piece over, cover with cloth, and press again from the right side of the fabric
    • Once the piece is fused, allow it to lie flat to cool and then trim away any little pieces of interfacing that extend beyond the fabric edge
    • Whichever type of interfacing is used, replace the pattern tissue on the garment piece to check that it has not distorted;  trim any excess interfacing
    • Marking is done on the interfacing
  • Fusible interfacing can also be used to support a fabric which on its own would not have enough body for the chosen style
  • Extra fusible interfacing can be applied in areas of the garment which may need extra support, for example a lapel collar or unusually shaped collar, hem or sleeve hem
  • If a more subtle and soft drape is desired, interfacing can be cut on the bias grain
  • Calico is often used in top areas of heavy jackets and coats for sleeve cap and underarm supports, chest pieces and saddle backs because that is the area of the garment which takes the whole weight of the garment during both wear and storage

Machine Stitching:

  • Rows of machine stitching will also stiffen fabric and can be used on under collars in place of hand pad stitching sew in interfacing.


  • The purpose of underlining is:
    • to provide shape and strength for the outer fabric where the fabric is delicate or unable to be fused, for example fine silks, satin, velvet, bouclé and fabrics with an embossed surface
    • to hide any trace of inner construction details on white or light coloured and shiny surface garments
    • to make an unlined garment more comfortable to wear
  • Fabrics which can be used for underlining include:
    • soft cotton flannelette (to create a little bit of loft and/or to add warmth) – be sure to prewash as flannelette shrinks considerably
    • silk organza
    • cotton batiste or lawn
    • cotton muslin
  • Underlining pieces are cut the same as the garment pieces and hand basted together just inside the seam line – they are then sewn as if they were one layer
  • Seam allowances, hems and other inner details can be stitched by hand to the underlining to keep them flat and in place


  • The purpose of interlining is:
    • to provide extra warmth to a garment, or
    • to add loft to otherwise flat surface/thin fabrics
  • Fabrics which work well include:
    • thin quilt wadding(batting) in either wool, cotton or bamboo, and
    • flanelette (be sure to wash it first in hot water to deal with initial shrinkage).

4 thoughts on “The Importance of Inner Structure Part 1

  1. Hi Alison. Your ‘Couture Workshop – Finishing the Edges’ that I attended last Sunday was both enjoyable and informative. I am looking forward to your next ‘Couture Workshop’. Many Thanks, Lizzie

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