Drafting Demo: the Rail Fence Block

Hello Friends and Welcome Back!

This is the second part of my mini series focused on the rail fence block. Last week, I shared some research on the history of the block, including many names it has held and other blocks that have been called rail fence. If you want to check that out, you can find it here.

Continuing the topic of rail fences, this week I’ll be sharing my way of drafting the block, including how to calculate cutting instructions, and two ways to construct the block.

Most block patterns can be broken down into a handful of basic shapes which makes it really easy to calculate the sizes you’ll need to cut everything. If you're not the type of person who is mathematically inclined, don't worry friend, you're not alone! The basic rail fence block is made only of rectangles; this makes it really easy for beginners since you won’t have to deal with any strange angles. This also allows you to make the quilt without calculating anything before you begin, if this appeals to you, skip down to the section “Making a Rail Fence Block without Calculations.”

There are also computer programs that can calculate everything you would need to make your quilt blocks, a really common one I’ve heard of is Electronic Quilt or EQ, but I believe there are others. I prefer doing all my drafting on paper though, so I’ve never used any of these programs and can’t provide any additional information about them.

Drafting the Rail Fence Block

A note before we start drafting; I use inches for my quilt measurements because those are the units on my quilting rulers, but the same process is also applicable to whatever units you are most comfortable using. For reference, 1" is about 2½ cm.

I like to do a little bit of planning before I start into the math. I find it’s really helpful to visualize the finished quilt by starting with a doodle or diagram to indicate strip width, block size, value placement, and other important details. I like to use grid paper and a mechanical pencil for my drafting. The grid lines help me to draw straight lines and keep my spacing even, and mechanical pencil makes very precise and fine lines, and is also erasable if I make any mistakes.

The rail fence is essentially a four patch; start with that basic shape, then add the desired number of strips.

A rail fence block can have any number of strips. You can see from the drafts I made in my journal that there are a wide variety of ways you could create a rail fence block. You can use any number of strips per unit and any combination of different strip widths.

If you’re like me and would like to push off the math a little longer, you can experiment with colour and value placement by drawing up several variations of your block. You can create a lot of different effects depending on how you use colour and value. If you don’t want to draw them all out by hand, there are a lot of digital drawing programs that can help speed up the process. The program I use to make the diagrams used in my posts is called Krita, it’s a free digital art program, if you’re interested in trying it for yourself, check out the Krita website.

Rail Fence Calculations

To get started on the math, you will need to decide on a measurement for either the size of the finished blocks, or the width of the finished strips. Seam allowance will be added later, so ignore that for now. I like to have a calculator on hand to double check my calculations, I use the default calculator app on my smartphone.

I will be using formulas based on the following variables:

Width of finished block = x

Width of finished strip unit = y

(the width of the finished strip unit is also equal to the length of each finished strip)

Width of finished strip = z

Number of strips per unit = n

If you want to start with the size of the block, divide it in half to get the width of the strip unit.

x/2 = y

From your sketch, determine how many strips will be in each strip unit, and if each strip will be of equal or unequal width.

For a block where all strips will be the same width, divide the width of the strip unit by the number of strips.

y/n = z

This might result in really strange measurements, for example, if you wanted your 6” strip unit to contain 5 strips instead of 4 in the example above, using this calculation would result in strips at 1.2” or 1 ⅕”. I would increase this to 1 ¼” which would make my strip unit 6 ¼” and my finished block 12 ½”, which is not a big change from my original values but makes measuring a lot easier.

If you want to make your strips a variety of sizes, the calculations become slightly more complicated. I like to think of each strip as a fraction of the whole, multiply the width of the strip unit by the fraction you want it to occupy.

y(fraction) = z

In my example, I individually calculated most of the different sized strips, then gave all the remaining width to the last and widest strip. Doing so ensures that the total sum of all the strips will equal the unit width like it’s supposed to, and I won’t accidentally end up with a block that’s too small.

If you would prefer, you can also start with the width of the strips and use that measurement to determine the finished block size. If your strip width was taken from an existing piece of fabric, such as a pre-cut jellyroll which contains 2 ½” strips, you will need to subtract the amount needed for seam allowance before proceeding with calculations. In the case of this example, you will need to subtract 2 seam allowances at ¼” each for a total of ½” removed, so the width of the finished strip would be 2”.

To calculate the width of the strip unit using uniform strip sizes, multiply strip width by the number of strips per unit.

z(n) = y

If you want to make a unit using strips of variable sizes, you will need to add together every different strip width.

z + z + z + z + … = y

Once you know the width of the strip unit, multiply the width of the strip unit by 2 to get the finished block size.

2y = x

Adding Seam Allowance

As mentioned earlier, all of these measurements will be for the finished sizes of each piece, so the next step is to add seam allowance. The standard seam allowance used in quilting is ¼”, but if you would like to make yours wider or narrower, feel free to do so. Regardless of what size you decide to use, make a note of the seam allowance somewhere in your pattern instructions so you won’t forget, and so you can share it with friends if you’d like. I will be using a ¼” seam allowance.

Each strip will need to be cut to the width of the finished strip plus the left seam allowance plus the right seam allowance.

z + ¼” + ¼” = width of cut strip

Many people will add their two seam allowances together before adding them to their finished strip size. Total seam allowance = left seam allowance + right seam allowance

¼” + ¼” = ½”

In my case, I would simply add ½” to all my finished dimensions. In the example of cutting strips;

z + ½” = width of cut strip

You will also need to apply seam allowance to the strip units (y + ½”) and to the finished block size (x = ½”) so they can be squared off before being joined to the next piece of the quilt. Squaring off your pieces during construction ensures that there is as little variation in block sizes as possible and will help you catch a mistake in the cutting or piecing earlier.

Assembling the Rail Fence Block

Rail fence blocks are really quite easy to assemble, however the method you choose to use will depend on the size of the fabric you’ll be starting with.

Strip Piecing

To strip piece a rail fence quilt, begin by cutting your strips at the width calculated above, and across the longest side of your fabric. Cut as many strips as are needed in each unit.

Sew the strips together along their long sides, pressing the seams as you go.

Once all strips have been added, sub cut the strip set into squares using the strip unit width measurement calculated previously. You should be able to cut multiple square strip units from each strip set.

Select four square strip units and assemble them into a rail fence block by alternating between horizontal and vertical orientation of the strips. Trim the block using the block width measurement calculated above.

Continue making blocks until you have enough to make a quilt of your desired size.

Some of you might recognize this method (and the diagrams) from my Rainbow Railfence pattern. Many quilters enjoy the strip piecing method because you don’t need to cut every strip in the quilt top individually, and there are fewer edges to align, so you won’t accidentally make your unit so uneven that it can’t be squared off.

This method works best using larger pieces of fabric, including yardage, large remnants, and fat quarters, or by using pre-cut strips, such as jellyrolls. If you really want to try this method, but only have smaller scraps to work with, you could piece together like fabrics into long strips, just beware that you don’t make them too muddy by including too many different fabrics, values, and patterns.

Piecing Units Individually

If the fabric being used is not long enough to strip piece, you could piece each block individually instead. Individually piecing each block is most commonly done when using smaller remnants and scraps.

Cut the strips using the strip width calculated above for the width, and the strip unit width for the length. I like to include an additional ⅛” or ¼” on the length; this isn’t necessary if your unit only has two or three strips in it, but with five or more strips per unit, it is very easy for the strips to fall out of alignment as you go, and you may not be able to trim it to the right size.

Sew the strips together along the long edge, pressing seams as you go. Once assembled, trim the strip unit to the strip unit size calculated previously. Make four of these units.

Assemble four strip units into a rail fence block, alternating between horizontal and vertical strip orientation. Trim the block to the block width measurement.

Continue making blocks until you have enough to make a quilt of your desired size.

Making a Rail Fence Block without Calculations

If you are the impulsive type, don’t enjoy planning, or really hate math, you can also make a unique and beautiful rail fence quilt without all that extra planning to complicate the process. While you won’t need to do any of your own calculations for this method, you will still need to keep track of certain measurements, so I recommend having something on hand for recording those.

To start, you will need a bunch of fabric strips. These could be remnants from other projects or strips you’ve cut just for this project, the strips don’t even have to be the same width! If using a standard ¼” seam allowance, minimum strip width will be ¾”.

Sew your strips together into a unit. Once you think the unit is wide enough, square it off. Take a note of the size of your first unit so you can create more of the same size. Make 4 units, then sew them together to make a block, alternating the units between vertical and horizontal strip orientation as shown below.

Repeat this process until you have enough blocks to make a quilt top of the desired size.

If using this method, I recommend first grouping the strips by length. Long strips can be pieced together into long strip sets using the strip piecing method mentioned earlier, then subcut into squares. Units made from shorter strips will be limited to the length of the shortest piece, and will need to be pieced individually following the second method from earlier.

Thoughts from VA

I think the rail fence is a really great beginner friendly block. It is simple to assemble, is super versatile, and allows for a lot of creative freedom. Sure, I might be biased because it was the block used in my first quilt, but I've had such an amazing time learning from and working with this block over the past few years.

Remember friends, this is your quilt, so make it your own! The strip units can all be the same, or you could make each unique. Use colours from the world around you that bring you inspiration; look at your favourite photos, drawings, paintings, book covers, or flags, reference the things that make you happy! Most importantly, have fun with your creation, that's the best way to learn.

If you make a rail fence quilt of your own using my drafting method, please leave me a comment letting me know if my instructions were helpful or not, I appreciate any feedback. I would also love to see your quilt whenever you're ready to share it! You can tag me on Instagram, @vafibrearts, or post a picture in my VA Fibre Arts Facebook group.

As Always Friends, Keep Creating,

VA