Trouser Zipper

[nailclipper]

Hi guys, have a zipper construction question. (Note am a beginner)


Is there a reduction horizontally over entire length of zipper of 1/4"?


I noticed my trousers zipper is hidden by 1/4", left front over right.

Or do you guys add allowance for zipper, from front waist to zipper notch.

[Gerry]

If youtube vids are anything to go my I'm fairly unique in doing this, but I mark in 'under-lap' for the RHS.

I mark the cloth with the left side of the pattern facing down and draw a line for under-lap, parallel with centre-front (which already has seam allowance), graduating it into the crotch curve at the bottom. Ready to wear trousers tend to go for a 1/4 inch underlap, I prefer 3/8 th of an inch. Once the trousers are cut, the LH front is further cut to rid it of the marked underlap, leaving additional cloth only on the RHS.

Most tailors don't bother, it seems, in which case material is technically robbed from the RHS. Though everything can be re-measured and evened up. This always seemed a bit backwards to me so I've never done it and don't really know the detail.

Do what makes sense to you?

[TTailor]

The draft I use is nett at the centre front line so I add seam allowance to allow for the zipper to offset 1/4".

I cut a 5/8" (1.5 cm) allowance in the zipper area for both fronts.
The zipper is sewn offset by 1/4" on the right front and I cut the excess on the left front down to my standard 1cm.

[nailclipper]

mark cloth with left side of the pattern facing down and draw a line for under-lap, parallel with centre-front (which already has seam allowance), graduating it into the crotch curve at the bottom. Ready to wear trousers tend to go for a 1/4 inch underlap, I prefer 3/8 th of an inch. Once the trousers are cut, the LH front is further cut to rid it of the marked underlap, leaving additional cloth only on the RHS.

material is technically robbed from the RHS.

Thanks Gerry, thought it was the LHS that got robbed.

If I understand it right, your method just adds seam allowances and doesn't change the hip width (or any width).


I'm curious on this as I see many trousers on IG with front side pockets being pulled.

Also, I usually draft the front hip without any ease, (i.e. Hip/4).
This helps to achieve a cleaner front for flat front trousers, or builds with a big increase in waist to hip.

[nailclipper]

The draft I use is nett at the centre front line so I add seam allowance to allow for the zipper to offset 1/4".

I cut a 5/8" (1.5 cm) allowance in the zipper area for both fronts.
The zipper is sewn offset by 1/4" on the right front and I cut the excess on the left front down to my standard 1cm.

Like Gerry, if I got it right, the draft is nett and only adds seam allowances, right?

[nailclipper]

So if I add 1/4" to only the Front right hip (on the rise), that should make the trouser fit better.

Also have another question on the zipper placement.

How high up do you place the zipper notch? (from the crotch line up)

From pictures, it looks as if most place the zipper notch around 2" above crotch line.

It seems a little troublesome when nature calls.

I'm thinking 1 / 1.5" would be better.

[Gerry]

Thanks Gerry, thought it was the LHS that got robbed.

If I understand it right, your method just adds seam allowances and doesn't change the hip width (or any width).

[Edit: With the conventional method] The left side overlaps the right, so the right tucks underneath and material has to be found to create that under-lap. In that respect, material is robbed from the right.

In reality, the left will be pulled over towards the centre front somewhat. If there's any noticeable discrepancy, then side seams can be adjusted. Either way, the width across the front is shortened by a tiny amount - initially, at any rate, until an adjustment is made (if necessary). This is why I prefer to add extra width to the CF/fly seam of the right hand side (no, I don't touch the side seams and there's no net loss/gain in width across the front).

Re zippers, ready to wear use shorter zips. Cheaper and easier to install. Bespoke flies tend to be longer. How low you go is a matter of preference and, often, is determined by the length of zippers available to you.

[nailclipper]

Yeah with zipper being in the centre i guess it pulls somewhat to either side.

Also, regarding zipper length. Do you draw the curve after the zipper notch?

It seems easier to place the zipper on a straight line as opposed to following the front crotch curve.

eg. If my straight line is 9" but i want a 10" zipper, should I draw the curve from 10" onwards?

[Gerry]

Yeah with zipper being in the centre i guess it pulls somewhat to either side.

The zipper isn't in the centre. In men's trousers it's always offset to the left of the centre-front crease of the LHS. It's just that when wearing trousers, the fit will 'settle' in such a way that the left tends to be pulled over a little if no compensation is made for the loss of fabric created by the 'under-lap'; but, as mentioned, I don't use the standard method so I'm not the person to advise you. To my mind it's a lot easier to add more width to the fly seam on the RHS.

Also, regarding zipper length. Do you draw the curve after the zipper notch?

It seems easier to place the zipper on a straight line as opposed to following the front crotch curve.

eg. If my straight line is 9" but i want a 10" zipper, should I draw the curve from 10" onwards?

No, you always draw the curve then decide where you want the zip to come down to. As a rule of thumb, the crotch curve starts at the top of the pubic bone (round about the seat line for many). Older style trousers take it a little higher. Don't forget that these forks determine ease in the crotch area. Overly scooping them, or bringing them down too low, is going to result in a squeaky voice for many. Or the Robert Plant 'camel tongue' look.

Bespoke tailors use special zips that are curved at the bottom, making it easier to sew them in place. An alternative is to straighten the curve out when sewing, to align it with the edge of a standard zip. Not ideal, but it works.

[Gerry]

Taken at random, to give you an idea of the type of zipper I'm talking about (I'm not endorsing this company or the zipper - haven't used either):

https://www.ebay.co.uk/itm/161706278546

[nailclipper]

Very interesting, I use the same brand but the straight regular version. Didn't know there was a curved version.

Will try to shape the straight zipper that I have haha.

Got you on the zipper positioning and crotch curve. Its cool, always good to learn how others do stuff. Even better when its different so I can try to figure which works out better!

[Greger]

There are a couple of books that I can think of off the top of head that have pattern systems for trousers that would help you.

https://archive.org/details/tailoringsuitspr00poul/mode/2up
Tailoring suits the professional way by Poulin, Clarence

https://www.scribd.com/document/121542775/How-to-Make-Men-s-Clothes
How To Make Men's Clothes by Jane Rhinehart

[Greger]

Where I place the zipper notch depends upon how long the zipper is. Place the top of the zipper teeth about 1/8 inch below where the waistband stitching goes. Follow the zipper down, and part way around the curve, to the bottom metal piece. 1/8 inch below that is where I cut the notch. When cutting the fly I extend the fly past the notch about 5/8 inch. Seems to be a good length beyond the notch.
This method avoids cutting the zipper, unless it really is to long.

[Gerry]

This is an example of the 're-jigging' approach. Not something I do (for reasons explained above), but valid and commonly done:

https://www.youtube.com/watch?v=hsMSFUw7TRw

[Schneiderfrei]

In the spirit of the old forum, in tailoring practice, there are not really any rules as such.  Maybe the tailor got a good deal on 17cm zippers; the zip must reach the band, ultimately that will determine the notch.