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Author Topic: Altering Trouser/Pant patterns  (Read 274 times)

June Moran

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Altering Trouser/Pant patterns
« on: February 26, 2018, 11:47:58 AM »
I never made trousers when young as I loved dresses but now have to wear trousers almost all the time.

However I don't know where to start altering a commercial pattern for elastic waist trousers as I measure waist 39" and hips 40". Obviously I have a protruding stomach! I assume I start with my hip size and adjust for stomach and waist?

I'm confident making bodice alterations and will make a muslin but any suggestion would be appreciated.

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Re: Altering Trouser/Pant patterns
« Reply #1 on: February 26, 2018, 11:48:23 AM »
If you're doing a pattern that uses a full elastic waist, the alterations for waist are already done for you, because they've just made the top as wide as the hip, and are letting the elastic bring in that inch at the waist.

The major alterations you'll actually be facing are the shape of the crotch curve, the slant of the waist, and the fit of the leggings.

Have you located a pattern you want to try?

If so, here's how I suggest you proceed, after you choose a plain, preferably light colored, fabric similar in drape to what you want for the finished trousers, and procure a twill tape or piece of selvage or a bootlace large enough to tie around your waist. Elastic crawls, and for fitting purposes, you don't want it to do so.

1) Add 2"/5 cm of height at the waist for fitting purposes.
2) Increase seam allowances to 1" (2.5 cm)
3) Cut the pattern pieces meticulously on-grain.
4) Before sewing anything together, take each leg section and fold it in half lengthwise, matching the inseam/hem corner and outseam/hem corner. Press the crease you get straight up the leg, from hem to waist, or chalk it in on the fabric with something that will show up well in photos. Do that on both legs, front and back. That is the actual grainline of the pattern, despite the pattern company's offset wimpy little arrows.
5) Mark some horizontal balance lines at the fullest part of your belly and backside, at crotch level and probably about knee level (make a guess... exact placement is not critical). These lines must be perpendicular to the grainline. Chalk or mark those in with something you can see in photos.

Sewing order from here on out is going to sound like heresy, but it makes it easier to fit your pattern:

1. Construct any pockets that are part of the front design of the pants, like the J front pocket on jeans, and *sew them shut*. If there are pockets that will be inserted in the side seams, just ignore them for now. We don't want the pockets to gap open while you're fitting, giving you misleading information on ease, etc., which is why you sew them shut.

2. Sew the two fronts together at the crotch seam WITH THE CROTCH SEAM ALLOWANCE TO THE OUTSIDE OF THE PANTS*. Do not press or clip this seam allowance.

3. Sew the two backs together at the crotch seam, just like you did on the front.

4. **Sew the joined front to the joined back at the side seam and inseams, with the seam allowance to the inside of the pants. Press the seams open.

5. Press up the hem at least an inch shorter than you think you'll wear them. You don't want the hem touching the floor or your feet, so the legs can fall free.

5. Put on your very peculiar-looking pair of pants, with the crotch seam allowance on the outside, and hoist them up till they are comfortable. Tie the pants around your middle with the twill tape (selvage, bootlace...) -- you want the twill tape to be tight enough the pants aren't going to move without help, but not so tight you can't breathe or you feel like you're being cut in half.

6) Stand in front of the mirror and look at the results. If the pattern is perfect for you, the side seams will be straight up and down, the grainlines on the legs will be straight up and down, and the horizontal lines will all be parallel to the floor, front and back and in side view. The crotch will feel good, there will be no wrinkles anywhere, and when you sit, the waistline of the pants will not move and you'll feel comfortable. That's in a perfect world.

In the real world, you'll start by straightening the pants so the grainline on the legs are vertical and the horizontal lines are as horizontal as you can manage just by pulling the pants up and down at the waist under the twill tape. Now sit. Does the back waist remain where it was, or does it want to pull down? If it pulls down, we need to tinker with the shape of the crotch seam, and possibly with the amount of crotch extension. I'm going to stop there on fitting instructions till you've had a chance to tell us what you discover.

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*Crotch seam allowance sewn to the outside lets us tinker with the shape of the crotch seam without needing to trim and clip the curve, which can be useful.

** Sewing the complete front to the complete back lets us tinker with the amount of crotch extension easily.

ablemable

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Re: Altering Trouser/Pant patterns
« Reply #2 on: February 26, 2018, 11:49:14 AM »
Thank you, Shannon, for your never ending patience. I have printed out your post. It encourages me to start again to try for a TNT pattern. I have followed all the other "trouser alteration posts" with interest, there is so much to learn. Thank you!

WillieMike

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Re: Altering Trouser/Pant patterns
« Reply #3 on: February 26, 2018, 11:49:47 AM »
Thank you so much! I too have printed this out. Pants are in the queue for this week.

db415

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Re: Altering Trouser/Pant patterns
« Reply #4 on: February 26, 2018, 11:50:29 AM »
The idea of the crotch seam allowance sewn to the outside so the clipping of the curve is not an issue during fitting is a lightbulb moment for me! Thanks Shannon

June Moran

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Re: Altering Trouser/Pant patterns
« Reply #5 on: February 26, 2018, 11:51:24 AM »
Thank you so much for your detailed post. It means I can proceed more confidently