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Joining granny squares with a single crochet seam that holds its shape

Few techniques feel as satisfying in a handmade project as the moment a stack of completed granny squares finally becomes a single, cohesive blanket or garment. The single crochet seam is one of the most popular ways to bring those squares together because it creates a tidy ridge, lays flat without too much bulk, and works for everything from a cosy couch throw to a light summer top. For Australian makers who spend winter stitching through cold southern evenings or summer arvos at the kitchen table, this joining method is reliable enough for heirloom pieces and forgiving enough for newer crocheters.

Before picking up the hook, it helps to understand a few small decisions that change the look and feel of the finished seam. Yarn weight, hook size, and how the squares are blocked all play a part in whether the final piece drapes softly or sits firmly. The krwknitwear.com library of patterns and tutorials offers a great starting point if you want to see how this join behaves in real projects before committing to a full blanket.

Preparing your squares so they sit flat

Crocheted squares almost always curl a little at the edges, especially when the centre uses taller stitches than the border. Before you join a single one, give each square a gentle wash in lukewarm water with a touch of wool wash, then press out the excess moisture in a clean tea towel. Pinning the squares out on a foam mat to the measurements given in your pattern helps the edges line up neatly, which in turn makes the seam much easier to work.

If you are working with cotton or a cotton blend — a common choice for Australian summer weight projects — the squares will often dry a little stiff after washing. A light steam from a distance relaxes the fibres without flattening the texture. Many makers at weekend markets in Adelaide and Brisbane swear by leaving their squares pinned overnight so the corners settle into clean ninety-degree angles. When all four corners match, joining becomes far less fiddly and the seam looks crisp from both sides.

For acrylic yarns that hold their shape better than wool, blocking is still worth the effort, particularly if the squares were made at different tensions. A quick spritz of water and ten minutes under a towel is usually enough. The goal is not perfection but consistency — every square should behave the same way when you hold it next to its neighbour, otherwise the finished throw will pucker in places you would rather it did not.

Picking yarn and hook for a neat join

The yarn you choose for seaming should be the same fibre content and weight as the squares themselves, or as close as possible. Using a thicker yarn than the project calls for will puff up the seam and add bulk, while a thinner yarn will pull the edges together and create a rippled effect. For a classic granny square blanket made from 8-ply acrylic, an 8-ply seaming yarn on a 4mm hook tends to give the firmest result.

Many Australian makers turn to local mills such as Bendigo Woollen Mills in Victoria or Morris & Sons in Sydney for natural fibre options that handle beautifully in seams. Heirloom yarns, sold at Spotlight and most independent haberdasheries, are a familiar choice for traditional granny square projects and have a long history in home craft across the country. Whatever you choose, wind off a small bobbin of seaming yarn before you start so the working strand does not tangle with the main ball sitting beside you on the couch.

The hook size matters more than people expect. Going down half a size from the hook used for the squares themselves often produces a tighter, more even seam that does not gap. If the join looks loose or holey, drop the hook another quarter size and try again. If it pulls the squares into a slight cup, go back up. A handful of test stitches on two swatches is worth the extra five minutes before committing to a full blanket.

Working the single crochet seam step by step

Lay two squares side by side with right sides facing up and edges aligned. Thread your yarn onto a yarn needle if you prefer sewing, or work the join directly with a crochet hook for the classic single crochet seam. Insert the hook through the back loops only of both squares — that little strand at the top edge of each stitch is the one that gives the seam its defined ridge. Yarn over and pull through both loops, then yarn over again and pull through the two loops on the hook to complete the single crochet.

Keep your tension even as you work along the edge. The single crochet seam naturally tightens slightly once you let go, so it helps to hold the work up every few centimetres and check that the squares are sitting flat and not pulling in at the corners. When you reach a corner, work three single crochets into the same stitch space so the join turns the corner without a harsh angle. This little trick is what allows the finished blanket to lie smoothly on the bed rather than bunching at the joins.

For joins that need a bit more flexibility — say, along the shoulder seam of a cardigan or the side of a jumper — work through both loops instead of the back loops only. The seam will be slightly flatter and a touch stretchier, which is often exactly what you want in a garment. Both versions are worth knowing, because the same granny square motif might be used for a stiff cushion cover in one project and a drapey shawl in another. Keep a note in your project book about which method you used so you can replicate the result later.

Joining in the round or flat, and why it matters

Most granny square blankets are joined flat in rows or strips, then seamed together at the end like a patchwork quilt. This approach is great for large projects because you can work on the layout as you go, rearranging squares until the colours balance. Lay the strips out on the floor in front of the telly, take a photo for reference, then stack them back in order before joining. Many Australian craft groups use the floor of the local community hall for exactly this kind of layout session on a Sunday morning, spreading squares across trestle tables borrowed from the RSL down the road.

For garments and accessories that need to be seamed in the round — think a granny square cardigan or a circular yoke — the single crochet seam can be worked continuously around the project. This produces a spiral-like join with a subtle stepped effect where each round meets the next. Some makers love that visible spiral as a design feature, while others prefer to finish the round with an invisible join by slip stitching into the first stitch and pulling the yarn through to the back.

A flat join, where the pieces are placed with wrong sides together and the seam is worked from the right side, gives a slightly raised ridge on the public side of the fabric. A flat join worked from the wrong side, with right sides together, hides most of the seam inside the work. The choice comes down to whether you want the join to be a feature or to disappear. For a chunky winter throw meant to drape over the back of a couch in a Tasmanian or Victorian home, a visible flat ridge can be a lovely textural detail.

Finishing the seam and caring for the finished piece

Once the seam is complete, weave in the ends with a tapestry needle, running the yarn under several stitches on the back of the work before trimming. For blankets and garments that will see a lot of use, double back and weave the tail in two directions for extra security. A dot of clear fabric glue on the knot can help if the yarn is particularly slippery, though most wool and cotton blends felt enough that this is rarely needed.

Give the finished piece a final block before gifting or using it. Lay it flat on a clean surface, ease the seams into shape with your fingers, and let it rest overnight. For wool blankets that will spend winter on the bed in a colder climate, a gentle wash in a wool detergent every few months keeps them fresh without felting. Cotton throws used in Queensland or northern NSW tend to need a wash more often because of the humidity, so a light blocking after each wash becomes part of the routine.

Storing the finished blanket in a breathable cotton bag rather than plastic keeps moths and mildew at bay, especially during the warmer months when storage spaces can get damp. A lavender sachet tucked into the bag is a charming old-school touch many Australian makers still use, and it keeps the cupboard smelling lovely. With the seam finished and the piece cared for, the granny square project is finally ready to be enjoyed for years to come.

Smart habits for a smooth join every time