Sew a pencil skirt with a back vent

A pencil skirt with a back vent is sewn in six stages: the front and back darts, an invisible zip at center back, the center back seam with the vent extensions, the side seams, a waistband or a waist facing, and a blind hem. The vent is a pair of extensions on the two back pieces: the seam is stitched down to the top of the vent, then diagonally across the extensions, and the left extension lies over the right when the skirt is worn. A knee-length skirt takes about 1 m (1 1/8 yd) of 140 cm (55 in) wide fabric and 5 to 7 hours, plus an hour for a toile.

What pieces does a pencil skirt with a vent need?

• Skirt front, cut once on the fold, with two darts at the waist.
• Skirt back, cut twice as a mirrored pair, each with a dart and a vent extension about 4.5 cm (1 3/4 in) wide along the center back below the vent point. The zip runs from the waist down the same seam.
• Waistband, a straight strip cut 10 cm (4 in) wide for a finished 3.5 cm (1 3/8 in) band, or a waist facing: a curved front facing cut on the fold and two back facings, 6 cm (2 3/8 in) deep.
• Notions: a 22 cm (9 in) invisible zip, fusible interfacing for the band or the facings and for the vent extensions, and a hook and eye or a button if you use the band.

Seam allowances are 1.5 cm (5/8 in); the hem allowance is 4 cm (1 1/2 in) so the hem has enough weight to hang straight.

How much fabric does a pencil skirt take?

Choose a fabric with body and a little stretch: stretch cotton sateen, wool suiting, ponte knit, stretch denim or a heavy crepe. A woven with 2 to 3 percent elastane is far more comfortable to sit in. Avoid thin, drapey fabrics, which wrinkle across the hip and show every seam allowance. The skirt is unlined; if your fabric clings, add a lining cut from the same pieces, 3 cm (1 1/4 in) shorter.

Why should you make a toile first?

A pencil skirt has 2 to 4 cm (3/4 to 1 1/2 in) of ease at the hip and almost none at the waist, so a difference of 1 cm shows. Cut the front and back from an old sheet or calico, sew the darts and seams with long stitches, pin the center back closed and look at it in a mirror, standing and sitting. The guide on making a toile explains what to mark, and the post on fitting a pencil skirt goes through the usual wrinkles at the hip, the waist and the hem.

How do you sew a pencil skirt with a vent step by step?

1. Cut and mark. Mark the dart legs and points, the end of the zip, the vent point on both back pieces and the hemline. Transfer the vent point exactly: it is where the center back seam stops.
2. Interface the vent. Fuse a strip of lightweight interfacing to the wrong side of both vent extensions, from the vent point to the hem. It stops the overlap from sagging and gives the diagonal stitching something to hold.
3. Finish the edges. Overlock or zigzag the center back edges including the extensions, and the side seams. It is far easier now than once the vent is assembled.
4. Sew the darts. Stitch from the waist to the point and run the last stitches off the fold. Press the front darts toward the center front and the back darts toward the center back over a tailor's ham. Sewing darts that lie flat covers the details.
5. Insert the zip. Sew the invisible zip into the open center back seam, from the waist down to the zip notch, with the teeth starting 1.5 cm below the raw edge. Do this before any of the center back seam is sewn: it is the easiest way to get a flat zip. How to insert an invisible zip shows the foot and the order.
6. Sew the center back seam and the vent. Right sides together, stitch from the base of the zip down to the vent point. Pivot there and continue diagonally, at about 45 degrees, across the top of the extensions until you reach their outer edge. On the right back as worn, clip the seam allowance horizontally at the vent point, up to the stitching, so the seam above can be pressed open while both extensions press toward the left.
7. Press. Press the center back seam open above the vent and the two extensions toward the left back. From the right side, the left back now overlaps the right and the diagonal stitching holds the top corner.
8. Sew the side seams, press them open, and try the skirt on. This is the moment to take the side seams in or let them out.
9. Attach the waistband or the facing. For the band, follow the same sequence as any skirt: interface one half, sew it to the waist, fold, stitch the ends, turn and stitch in the ditch. For the facing, interface the pieces, join them at the side seams, finish the lower edge, sew the facing to the waist right sides together, trim and clip, understitch the facing to the seam allowances, turn it inside, fold the ends under at the zip tape and hand stitch them. Tack the facing to the darts and side seams so it stays down.
10. Hem. Finish the raw edge. Fold each extension back on itself at the hem fold, right sides together, and stitch across it at the hem depth, 4 cm from the edge; trim the corner, turn and press. This gives a clean, square corner at the bottom of the vent. Then turn the hem up 4 cm and sew a blind hem by hand or with the machine's blind hem foot. How to sew a blind hem by machine shows the fold.
11. Secure the vent. From the right side, topstitch along the diagonal through all layers, or hand stitch the top of the overlap to the under layer with a few invisible stitches. Give the skirt a final press over the ham, with a press cloth on the vent overlap so it does not shine.

What goes wrong with a back vent?

• The vent overlaps the wrong way. The convention is left over right as worn. Check before you press the extensions, since the clip in step 6 is on one side only.
• The vent pulls open. The skirt is too tight across the hip or the seat, so the vent takes the strain. Let out the side seams a little above the vent; the vent itself is not the problem.
• The top of the vent puckers. The diagonal stitching was pulled tight or the extensions were not interfaced. Loosen the thread tension and press over a ham.
• The zip bubbles at the top. It was sewn with the coils closed or pulled through while sewing. Press the coils open before stitching and let the feed dogs do the work.

When is a vent the right choice?

A vent is needed on any pencil skirt at the knee or longer: without it the hem limits your stride to a shuffle. On a skirt above the knee the hem opening is already enough. A kick pleat gives the same freedom with the opening hidden behind a fold and takes more fabric; a plain slit is quicker but shows more leg and frays at the top unless it is bar-tacked.

Can the pattern be drafted with the vent already sized?

Sewly's pencil skirt pattern drafts the front and the two back halves from your waist, hip and waist-to-hip length, with a taper from 0 to 4 cm (0 to 1 1/2 in) at each side and a waistband or a facing. The vent is sized to the skirt length and left out when the skirt is too short to need it, and the guide lists the 22 cm zip, the interfacing and the fabric for 110, 140 and 150 cm wide fabric for your size.