How to Make Quilt Sashing With Cornerstones

Sashing and Cornstones for a Straight-Set Quilt

Make Quilt Sashing with Cornerstones
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Sashing is strips of fabric (plain or patchwork) that divide quilt blocks from each other. The strips can have squares or other types of patchwork adjacent to the corners of quilt blocks. The squares are known as cornerstones.

Sewing sashing between your quilt blocks is one way to add another design element to the quilt's layout. It has these uses:

  • Sashing frames the quilt blocks.
  • Sashing is often the perfect choice for a sampler quilt because it offers a bit of separation for patchwork blocks that would not look attractive when they are sewn side-by-side.
  • Sashing increases the quilt's dimensions.
  • Sashing can help you square up blocks that are slightly different sizes, using the same technique used to sew borders to a quilt.

It's easy to sew sashing to a quilt, especially straight-set layouts since they don't require triangles or strips with angled edges as on-point settings do.

Cornerstones Needn't Be Plain Squares

Quilt sashing can be continuous, with no cornerstones, but cornerstones are one more way to add color and visual interest to a quilt. 

  • The dark and light sides of half-square triangle units help link blocks and sashing.
  • Quarter square triangle units are another cornerstone option.
  • Try small four-patch cornerstone units—use their dark (or light) squares to create a continuous diagonal flow across the quilt.
  • Any square patchwork unit that works with the width of your sashing can be used to make traditional cornerstones.

Materials Needed

To make sashing and cornerstones you will need fabric, thread, measuring tools, cutting tools, sewing machine, and iron.

Sashing and Cornerstone Measurements

Sashing a Quilt
Janet Wickell

Determining the dimensions of your sashing and cornerstones is the first step. You can then calculate how much fabric you will need.

Sashing Width and Length

Sashing width is up to you, but unless very wide sashing is an important part of your quilt's design, try to avoid using strips that overpower the dimensions of the quilt blocks. Work with sashing that finishes at one-fourth of the block's width, or less. That means you would use sashing up to 3 inches wide (finished) for a 12-inch (finished) quilt block.

When you cut sashing strips, remember that you'll lose a total of 1/2 inch from their width after sewing strips to the quilt blocks.

Once you've decided how wide sashing strips should be, determining their length is simple—cut strips that equal the unfinished measurement of the quilt block. If your blocks are square, all of your strips will be the same length. If you're making rectangular quilt blocks, you'll need strips for each dimension.

Take care when making your quilt blocks, pressing as you go to ensure that blocks are the correct unfinished size. Even if they differ slightly, cut strips to equal the length the unfinished block should be. Most patterns tell you how wide and tall a block should be after it is assembled, but if your pattern does not, add 1/2 inch to the finished width and height of a block to determine its unfinished size.

Cornerstone Size

Cornerstones have sides that match the width of your sashing. For instance, if you cut sashing strips that are 3.5 inches wide, your cornerstone squares (or patchwork cornerstone units) should measure 3.5-by-3.5 inches (unfinished).

Determine How Many Sashing Strips and Cornerstones Are Needed

Make a sketch of the quilt's layout—nothing elaborate, all you need is a quick look at the basic design. Refer to the drawing above and ask yourself:

  • How many blocks will be sewn across in each row?
  • How many rows will the quilt have?
  • Do you want sashing on the outer perimeter of the quilt, or will you reserve that space for a first border?

Sketch in the sashing strips and cornerstones and count them. Use yardage calculation basics to be sure how much fabric you'll need.

Assembling the Quilt With Sashing and Cornerstones

Once you have the dimensions set, cut your sashing strips and cornerstones.

Follow these steps to assemble the quilt:

  1. Sew sashing units vertically between each quilt block in each row, and to the ends of rows if you've chosen that look. Press seam allowances towards the sashing strips. Repeat to assemble all rows of quilt blocks.
  2. Carefully align the ends of sashing strips to the ends of each block they're being sewn to. If the lengths match exactly, that's excellent. If they do not, fold the sashing strip crosswise to determine its midpoint. Determine the block's midpoint, too. Match midpoints and ends carefully before sewing to help square up the block.
  3. Sew cornerstones and sashing together to create the narrow rows that are placed between rows of blocks. Begin and end with a cornerstone unless you are not sewing sashing around the outer perimeter of the quilt.
  4. Press seam allowances towards the sashing, taking care not to stretch the long narrow rows. Repeat to assemble all narrow rows. Use straight pins to keep fabrics from shifting.
  5. Sew all rows together, matching seam intersections carefully. Press the quilt.

How to Vary the Quilt Sashing

Quilt Sashing instructions
Janet Wickell

This Sailboats quilt is constructed with simple sashing strips and squares, but with variations in color value. The mixture of light and dark sashing creates visual movement.

Use Frames Around Blocks to Create Sashing

Make Quilt Sashing
Janet Wickell

The frames that surround the center of these Friendship Star quilt blocks provide ready-made sashing and cornerstones. Using different fabrics from block to block results in a patchwork sash and four-patch cornerstones when all of the quilt blocks are sewn together.

These are just a few examples of the ways sashing and cornerstones can be used. Experiment and you'll find there is an endless number of ways to design sashing for a quilt.