How to Join Granny Squares: 6 Methods Compared
Why the Joining Method Matters
The way you join granny squares affects the finished look, drape, durability, and how much time the joining phase adds to the project. Some joins add a decorative ridge on the right side and become a visual part of the design. Others are nearly invisible on the right side but visible on the wrong side. Some add width between squares — important to account for in your square count. Others add no width at all. The same blanket with different joins can look like two different projects. Choosing a method is not just a technical decision — it shapes the final aesthetic.
Flat Seam Join (Mattress Stitch / Whip Stitch)
The flat seam join uses a tapestry needle and a length of yarn to sew squares together through their edge stitches. Whip stitch: hold two squares with right sides facing each other, insert the needle through the outer loops of both edges from back to front, repeat at even intervals. The result is a slightly raised seam on the wrong side, nearly invisible on the right. Mattress stitch: insert the needle between the edge stitch and the next stitch on each square alternately, working along both edges simultaneously. This creates a more invisible join — when pulled firmly, the two edges appear to merge. Flat seam adds minimal width (the yarn diameter only) and is the fastest joining method for makers who prefer sewing over crocheting. The drawback is that sewing tension is harder to keep even than crochet tension, and inconsistent seam tension creates wavy edges. Best for: makers comfortable with needle work, projects where an invisible join is the priority.
Single Crochet Join
Hold two squares with wrong sides facing each other (right sides both facing outward). Insert your hook through the outer loop of both edges simultaneously and work single crochet stitches along the entire edge. The single crochet creates a raised ridge on the right side of the work — this becomes a visible design element rather than a hidden seam. When done in a contrasting color, this ridge becomes a strong graphic feature and is often described as the 'puff seam' look. When done in the same color as the squares, the ridge is subtle but still visible on close inspection. Single crochet join adds approximately half a single crochet stitch width to each seam — on average 0.25–0.5 inches per join depending on hook size and tension. Account for this in your square count using the joining width field in the calculator. Best for: makers who want a decorative join, projects where the seam color adds to the design.
Slip Stitch Join
Identical setup to the single crochet join — hold squares wrong sides together, work through both outer loops — but replace each single crochet with a slip stitch. The slip stitch join lies flatter than the single crochet join and produces a visible but less raised ridge. It is faster than single crochet because slip stitches require no yarn pull-through step. The result on the right side is a thin raised line rather than the fuller ridge of the single crochet join. Slip stitch joins work best when the squares have a clean edge loop to work into — if your squares have finished edges that are uneven or have partial stitches at the corners, single crochet is more forgiving. Best for: makers who want a visible but lower-profile join, faster working time than single crochet.
Join-As-You-Go (JAYG)
Join-as-you-go attaches each new square to finished squares during the final round of crocheting. Instead of completing the final round independently, you work to a joining point, slip stitch into the corresponding stitch of the adjacent square, and continue the final round. This eliminates a separate joining phase entirely — each square is attached as it is finished. The seam on the right side is invisible; on the wrong side, the joining slip stitches are visible as small horizontal bars. JAYG requires planning the joining order before you start — typically working row by row, completing an entire row of squares before starting the next, joining each new square to the square above it and the square to its left simultaneously. For traditional granny squares, JAYG joins at the chain spaces, creating a seamless chain connection. For solid squares, it joins through the final round edge stitches. The main limitation: JAYG commits you to the layout before crocheting each square's final round. If you want to rearrange the layout after seeing all the squares laid out, JAYG is less flexible. Best for: makers who want no visible seam, projects where the joining process should be minimal.
Lattice Join
The lattice join (sometimes called the square join or grid join) fills the space between squares with a small crocheted square, creating a lattice grid over the entire blanket. Squares are left with a small gap between them — usually one or two chain spaces — and the gap is filled with a miniature granny square or solid square crocheted in place after all main squares are positioned. The result is a blanket where the joining itself is a design element, often in a contrasting color, creating a stained-glass window effect. The lattice join is significantly more time-consuming than other methods and adds considerable width — the gap between squares plus the fill square adds 1–2 inches per seam depending on the fill square size. It is best suited for projects where the join is intended to be decorative and the maker has planned the layout with the extra width in mind. Best for: advanced makers, projects where the join is part of the visual design.
How to Choose the Right Join Method
Start with the visual result you want. If you want the seams to be invisible and the blanket to look like continuous fabric: flat seam or JAYG. If you want a graphic element that emphasizes the grid structure: single crochet join in a contrasting color. If you want something between — a visible seam that does not dominate: slip stitch join in the same color as the squares. Then consider your working style. If you like to crochet: JAYG, single crochet join, or slip stitch join. If you prefer to batch-produce all squares first and then join: flat seam, single crochet join, or slip stitch join. If you want to keep the layout flexible until the very end: flat seam — you can reorder squares right up until joining begins. Finally, consider the yarn. Smooth, plied yarns show all joins clearly, so a flat or invisible join matters more. Textured, fuzzy, or bouclé yarns hide most join types equally — choose for speed rather than appearance.
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