Designers must know seam allowances and specifications

Certain themes seem to crop up over and over within a short period of time leading me to think I should post reminders about it. Today’s topic amounts to brief reminders about seam allowances and the responsibility of technical specifications.

Seam allowances:
First, if you don’t know anything about sewing and are obligated to provide this information to a pattern maker, sample maker, or sewing contractor, you can go to a thrift store and buy garments for the purpose of cutting seam samples to illustrate your wishes. Use these as call-outs for your sketch and label them by number to keep them straight (see pg 126+ in my book). Alternatively, you can safety pin cut seam samples to specific locations on a garment if you have one. You may think this presentation isn’t very professional but service providers will be delighted.

If you know something about sewing but aren’t an expert, be aware that in production sewing, seam allowances vary. They are not generic and uniformly applied like in home sewing with allowances 5/8″ all the way around. Seam allowances vary depending on the preferred seam which is based on the material and desired effect. Once each individual seam is selected, the type of machine needed to do it can be determined. It is the machine that determines the seam allowance. For what it’s worth, a designer is not expected to know all of this (although it is nice if they do) and can request the pattern maker to do what is typical.

If you are particular and for whatever reason have decided you have to do this and don’t know what allowances are typically used for a given operation, you can use the strategy I described to non-sewers in the first paragraph. There are also several posts on this site about it; see The rules on seam allowances and The rules on seam allowances pt.2. Personally, I think you should determine what kinds of seams you want (if you can) and where you want them and leave the rest of it to the pattern maker. The alternative can be worse. It is beyond me to understand why a designer must have a half inch seam allowance on a collar or neckline. Or worse, 5/8ths everywhere leaving others with the impression you’re using a home sewing pattern. The latter are avoided because these usually won’t sew together precisely and can have a range of other problems that unnecessarily increase problems and consequently, costs.

Who has responsibility for technical specifications?
In the strictest sense, technical specifications are a designer’s responsibility and are often or usually conveyed in a technical sketch. That doesn’t mean you must do it yourself but you are responsible for it being done. If you can’t do that, don’t fret; you can follow the guidelines above to illustrate what you want.

It is a bit different if you’ve hired a pattern maker to use their best judgement to do this for you in the process of making the pattern. While they have determined the best allowances and necessarily convey that information to the sample maker and/or contractor, the manner in which they convey that may not be in a format you expect or is amenable to your needs. Please understand this; if you want these specifications separate and apart from the scope of their duties and in a format amenable to your needs, you need to be very clear while also realizing this is not a service they are obligated to provide much less at no additional cost. I’ll be more specific:

If I’m working with known downstream parties, I may not specify allowances separate and apart because the allowances will either be printed on the pattern plot itself, obvious in the design of the pattern (notching allowances) or written along pattern edges. If the customer requests seam allowances for each pattern, it is a simple matter to do a screen capture (sample shown at right) or to write up a brief but complete list such as:

  1. Unless otherwise specified, all seams are 3/8″
  2. Collars, neckline and outside edges are 1/4″
  3. Sleeve hem allowance is 1.5″
  4. Sweep hem is 2″.

However, if a customer wants more than this, say what would amount to construction details or instructions with illustrations more typical of what one would expect in a tech pack, it won’t be free. It is also possible that the pattern maker doesn’t provide this service.  Illustration has always been the designer’s job so many pattern makers never had to learn to do it (well) or even care to do it. If you want specifications over and above the scope of the pattern maker’s responsibility, you can’t get upset if you’re expected to pay a fee.

I hope this has been helpful to clarify points that may have confused you in the past.

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  1. CCL says:

    I notice with many of our customers that they have no idea how much seam allowance they need for their clothing labels: we make everyone according to the customer’s specs and if they don’t know how much they need, our product will not work appropriately for their purpose.
    For clothing tags and labels, we recommend 1/8″ as standard, but sometimes they need 1/4″ or even as little as 1/16″, it depends on their application.

  2. Brina says:

    The Garmento Website looks interesting–I didn’t get a chance to look at all the stitches, but they have at least one of the hand stitched mislabeled. What they have as a basting stitch is not–it’s a seaming stitch. What they have for a pick stitch looks more like a running or basting stitch, although sometimes pick stitches can be longer that a pick.

  3. Brina says:

    Um, they have some of the serger/overlock stitches mislabeled as well. Ey-Yi-Yi, Shame because the swatches are nice and clear.

  4. Brina says:

    Okey–I’m thinking now I am wrong–I just would never use a hand seaming stitch to baste something–nor do I know of anyone that would–I would use a running stitch. And I thought that chain stitches were never considered safety stitch. Obviously my nomenclature differs. Sorry for the error.

  5. Kathleen says:

    The seam classes are the 751-a established by the US govt to ensure uniformity in contracts. It is quite old but has become the defector standard for better or worse. Somebody had to decide something because garmentos would never agree. Anyway, warts and all, it works for the most part if for no other reason than that we have a picture for comparison. People still call the seams by whatever name they learned for it so one begins to learn all the possible variations over time.

  6. RWU says:

    I should know this but I’m having a block (pun intended). Can a “block” (on/of oak tag) have seam allowances? What I really want clarification on is it typical for a cutting “template” of oak tag (or any heavy weight paper/material) to have seam allowances?

    Thanks! And your blog/site is fantastic!!!


  7. Beth H says:

    I know it’s been a few years since this discussion was active, but wanted to say, I worked for a custom clothing label and tag company, They would help designers make sure the labels and tags work with seam allowances and specifications. Thanks!

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