I know I’m a little out of sync here, since it should be a Bag Making Basics week, but a combination of starting Part 2 of the My Small World Quilt and a question from one of my IG followers this week about seam allowances led me to think it might be a good idea to take a look at why precision in seams is important, especially in quilting.

Quilting is basically a fabric jigsaw puzzle, and if your pieces aren’t all the right size, then they’re just not going to fit together nicely (well unless you go down the route of Uncle Hamish in Iain Banks’ The Crow Road, and just snip off bits until you can jam them in!)  With simple patchwork squares you can get away with dodgy seam allowance sizes as long as you’re consistent, but when you start to combine different sizes of square/rectangle and then take into account sections that have points, that’s when things all start going to pigs and whistles.

The way the My Small World Quilt is made is by constructing a combination of blocks of varying sizes, pretty much all consisting of many small pieces.  Here’s my Part 1 section for example:

In the above section we have different sized rectangles making up the blocks of flats, there are all manner of triangles in the shape of flying geese, quarter and half square triangles, and full and half equilateral triangles, there’s the odd rectangle for relief, and then, of course, there are the curves, both pieced and appliqued.  I’ve seen a few people mentioning that they’ve had ‘building subsidence’ (aka wonky tower blocks) in their construction so far, and the sails of their windmills have been getting rather blunt ends, so let’s take a look at the potential causes and how to solve them.

Now before we dive into the buildings, we need to stop to look at the concept of the 1/4″ seam allowance.  Let’s start with some fictional 4 1/2″ squares – if you draw a line 1/4″ from the edge of the square of fabric, and then place it right sides together with another square before stitching down that line, when you open it out to press it, you would imagine that it would come out at 8 1/2″ (having lost 1/4″ from each square in the seam allowance)


Except it won’t.  The thing is that while quilting cotton is not exactly heavy weight, it does have some thickness, and you will lose a smidge of fabric from each square in the fold as you open them out from the seam.  As you can see below, this is shy of the 8 1/2″ mark:


All those smidges will add up, and more rapidly than you would imagine.  Guestimating that the smidge above is 1/16″, by the time you’ve sewn a strip just 5 squares long, you could have lost as much as 1/4″.

Here’s where the ‘scant’ 1/4″ seam idea comes in.  To make your seam allowance and fold add up to the 1/2″ we’re expecting to lose with each seam, you need to move your needle half a smidge towards the edge of your fabric.  Yup, I know I just said half a smidge, and you have no frigging clue how big your whole smidge is, but here’s the thing – neither do I!  It will depend very much on your machine how your smidges are even measured – computerised ones make it rather easier to work out, but some experimentation with some scraps should allow you to work out how you need to set your machine up best.  It will also depend on how you’re measuring your seam allowance on your machine – you may be using a 1/4″ foot, or you may be using a standard foot and some kind of guide either on the foot or your machine bed.  Finally, how you press your seams will also make a difference, although as long as you are consistent you should be okay.

I will confess here and now that I don’t use a 1/4″ foot.  It’s not that they’re not available for my machine, heck it even came with one, it’s just that it wasn’t actually 1/4″, it was more like a 3/8″ foot and the way it was set up there was only a single teeny hole for the needle to pass through in the centre, so moving my needle wasn’t an option.  I could have Heath Robinsoned it, but frankly I couldn’t be arsed since my standard foot actually has a mark on it to show where 1/4″ is, and I know that from the moment I turn my machine on, when the needle automatically aligns to the left hand side, if I move the needle 2 places to the right I get the perfect scant 1/4″ seam.  I know several of you have just had heart failure.  I’m sorry.  Here’s my foot for my Brother NX 2000:

I do get accurate seam allowances though, promise!  Look at these pinwheels  – I lost a teeny bit of one of the navy points in the centre, but I embraced my inner Frozen and let it go (I promise the arrow above is straight, it’s just that the section was folded down so I could photograph this under proper lighting):

Back to those buildings and block issues:

Issue #1: Triangle points are getting eaten by the seam allowance.

Let’s look closer at one of those sets of geese:

There’s 3 potential seams to munch your points here when you join the blocks together, but in fact the first place when things can go wrong is when you make the individual goose block, because if that comes out the wrong size, it’s going to be downhill from there.

If the goose is too big all over, then your seam allowance is too scant, be less frugal ;o)

If the goose is a bit big in a few places, then you’re possibly not sewing a perfectly straight line – hey, things happen, the dog barks, the cat runs across your sewing table, a bomb goes off on the telly (okay, maybe that only happens to me), either way, you get a wee surprise and your hands jerk about a bit.  Alternatively you may be over zealously tugging at it when sewing on the bias and you’ve stretched it out of shape a bit.  Whatever the cause, it’s really important to measure and trim at each stage as you go.  I know, I know, it’s a total PITA, but it’s worth it, I promise!

If the goose and rectangles making up the bottom part of the arrow are the correct size but they aren’t sewn together so that their sides match perfectly, then you’ve set yourself a bit of a challenge with subsequent seams.  For example what do you align the edge of that rectangle to the right with, the top part?  The bottom?  On an angle between the two?  None of these are desirable, so look at how you’re pinning your pieces together, and pin accurately.

If you know your arrow is the correct size then either you’ve not kept a consistent seam allowance as you’ve joined it elsewhere, or you’re joining it to other blocks with dead wonky seams because… Actually I have no idea why, don’t do that!

Issue 2: Your flats have terrible subsidence, and one side of your top part of Part 1 is considerably lower than the other.

There’s no pesky triangles here, but there are lots and lots of wee rectangles, and this is where you will really see your dodgy seam allowances having an effect.  The 3 different buildings are sewn together in different directions – the two on the right are done vertically, while the one on the left is horizontal, so they will have crept out of shape in different directions, making it challenging to join them all together in a straight line.

There’s no way round it, get an accurate, scant 1/4″ seam, measure and trim at each step.

Issue 3: The whole section is kind of going at a slant.

If your top section is squint, then your bottom section is going to end up suffering the same fate – if you keep adding things at angles, well, you can’t really expect them to come out straight ;o)  Either embrace your unpicker and fix the seam allowance to sort your subsidence out, or be happy that your world is on a hill…

Issue 4: Pieced curves scare the bejaysus out of you, and after 3 rounds with the unpicker they’re all out of shape.

If pieced curves put the fear of god into you, then I suggest you invest in some starch and either a whole pile of pins or gain the balls to do it pinless.

The starch will help to stop the fabric being stretched out of shape, but I would suggest starching prior to cutting out, as I’ve found the liquid starch I use makes the fabric shrink a teeny bit.

If you’re pinning, find the centre of both sides of the curve being sewn together and pin there first, then work your way out to each edge.

If you fancy going pin-free, check out Leanne’s video over here on how to do that.

Issue 5: Applique is not your favourite

Nor mine, but check out my previous post on that.  Also, for the doors, leave the bottom edge open, it will be swallowed in the seam allowance.

Okay, I hope that helps, but if anyone has any questions, please let me know!