Calculating Sashing and Cornerstones
 

I hope that someone can/will help me with calculating Sashing and cornerstones for a block swap quilt that I will be making. I will have 12 squares that measure 12 1/2 inches before assembling. I plan to use a 4 x 3 array with 3 squares across and 4 squares down. How wide should the sashing be? I plan tp apply the vertical sashing first to connect the rows of three squares so next i need to know What length do I cut the horizontal sashing pieces to attach to the corner stones so that it will fit perfectly with my rows of squares and Sashing?

I hope this all makes sense! I usually follow a pattern and someone has already done all of the math!!!

Thanks!

It is up to you to determine how wide each strip is. I like mine @2" for a 12" block. So the width of the strip would need to be cut at 2 1/2" - I usually draw my grid on paper so I can count how many sashings and how many corner stones it will take. You also have to decide how you will treat the outer edge: Are you adding the sashing color as a border or are you extending the corner stones to the edge. Either works - I've done both.

Assuming you want to put a solid border around the outside you will need 8 strips 2.5 x 12.5 for the horizontal pieces. Sew the strips to the sides of your center block and attach the sides. That gives you the width of a row.

Then you will need 9 strips 2.5 x 12.5 for between the rows. You will also need 6 corner stones 2.5 x 2.5
Using the same seam allowance, sew long strip to corner stone to long strip to corner stone to long strip.

I make sure that I press the side sashing on the rows opposite to the corner stones. That way they will all nest nicely when I attach the two together. I hope that helps.

When the top is sewn you can measure across the center to get the correct measurements for the border.

Both the horizontal and vertical sashing should be cut the same size as the block, 12.5 inches. The width is up to you. I would lay the uncut sashing fabric on a table or board, then arrange some of the blocks to see what width you like with your blocks. There's no set rule. What ever width you decide on, add 1/2" for the seam allowance. For instance, if you think 2" sashing will look good, cut the strips 12.5 X 2.5. The cornerstones would be a square cut to the width, 2.5C2.5

Great explanation, MadQuilter! Thanks!

I do mine like MadQuilter does hers. I usually put the sashes and cornerstones on the outside edge also and then put a border whatever size I want around the quilt top.

Thanks, jingle! I can't wait until October to get all of the blocks so that I can start assembling. My guild did a pizza box swap so I haven't seen my box since January. Each month a member added a block according to my specifications. I asked for 12 inch finished blocks in black and white only.