Welcome back to Part 5 in my Pattern Fitting Series, “My Approach to Successful Pattern Fitting”.  If you’ve just found my blog and are interested in reading what motivated me to write and produce my own pattern fitting series it’s here, “I Can’t Take It Anymore ~ My Approach to Fitting”.  If you’d like to start your “Journey Back to Garment Sewing” or are interested in reading my pattern fitting series from the beginning it’s here, Part 1:  Measuring Properly. 
 
Seam allowances may “seem” (pun intended) to not be worth mentioning, however choosing to add the right amount can be very important.  Generally speaking, commercial patterns like the Big 4 usually use 5/8″ seam allowance which is moderately generous.  Working with 5/8″ seam allowance on a straight seam is easy, however working with 5/8″ around corners or curves can be more difficult.  Recently I’ve noticed on the semi-fitted shirt pattern, Butterick 5300 which I used for my photo illustrations, they used a 3/8″ seam allowance at the neck line and down the front facing.

Front neckline and facing showing 3/8″ seam allowance.

Back neckline showing 3/8″ seam allowance.
I think this is a great improvement to the traditional 5/8″ seam allowance in these areas.  It can not only make a part of construction easier it can also cut some time out of certain construction operations later.  For example:   Using a 5/8″ seam allowance at the neckline to attach a collar is more difficult than if the seam allowance was 3/8″.  Having a 3/8″ seam allowance makes the collar easier to manipulate around the curve of the neckline.  It’s easier to maintain accuracy also.  Then later instead of trimming, clipping and grading the seam allowance, you will just clip where necessary.  Many manufacturers use 1/4″ at the neckline to avoid trimming and clipping later which saves the operator time and the company money.
There aren’t really standard seam allowance rules in the industry per say.  There may be some standardization at different price points, but I’ve always found that each company I’ve worked with have their own standards.  Higher end clothing, which is where I have the most amount of experience, typically offers a more generous seam allowance.  Inexpensive RTW brands will tend to use a smaller seam allowance to be more cost effective.  Each manufacturer in which I was employed had their own particular standard which we as Designers would follow, however each was different.  The Bridal manufacturer I worked with used 1/2″ for her princess seams and 1″ for side seams and center back seams.  This was because each bodice was hand cut and then was pinned and fitted on her standard size dress forms and then sent out for production.  By allowing such a generous seam allowance, we were able to change dress orders to suit our clients needs.  If there was a cancellation on a size 6 in a particular style, we could have that bodice made into a larger size if necessary.  It allowed for flexibility within a reasonable size range.   Most Bridal gowns are altered to fit each individual bride at the bridal retailer and the extra seam allowance allows for those alterations without additional fees like a specially measured gown.  Another manufacturer I worked with used 1/2″ princess seams, 3/4″ side seams and 1″ center back seam allowances.  This was another high end ladies dress manufacturer that catered to mother of the bride and special occasion apparel.  Once again the generous amount of seam allowance was because these dresses were usually fitted at the retailer.    Better garments will always have a more generous seam allowance to allow for alterations later.
The most important thing to keep in mind with any seam allowance is accuracy.  If you are sewing a princess line garment, there are 7 seams to be sewn all the way around your garment.  If you add even the smallest 1/16″ to each of those seams, your finished garment will end up 7/8″ smaller!!  That’s almost a full inch smaller.  Years ago when I was starting out in Fashion Design, I was assigned a sample maker to work with.  She was a very sweet lady, however she couldn’t adhere to the proper seam allowances in  her construction.  Consequently every time I did a fitting for a production garment that she sewed, my sample would be small.  This is a BIG issue in production and can be for you also.  When working in a production pattern situation where there are many operators, it’s important to be spot on to keep a consistent range of sizes!!  I’m sure you’ve purchased a RTW garment and went back to select a different color of the same style.  Have you ever noticed that if fit differently?  I sure have.  I have 3 pairs of cropped pants all the same size and manufacturer purchased at the same time in different colors.  They all fit just slightly differently because they were made by different operators.  The good news is that if you know you take a larger seam, you can allow for that during your drafting process to accommodate your preferences.
There a several criteria to keep in mind when selecting a seam allowance width for a particular type of seam.  I’m not going to delve to far into the world of different seam finishes in this post.   I could do a whole series just on the different types of seam finishes and allowances for each type of fabric.  I’ll keep that in mind for later if I find that there is an interest.  I recently was reading a vintage sewing technique book and found a seam finish that I’d never heard of before.  It’s called French piping or roll binding.  It involves binding the seam allowance with a doubled bias strip and then rolling the bias fold over the seam and hand stitching.  I will have to give that a try at some point.  I love learning “new to me” techniques!!
1.  Enclosed seams: There are certain seams, especially those that end up being enclosed like necklines, collars, facings and cuffs etc. that are much easier to construct with a smaller seam allowance.  The smaller the seam allowance, the easier it is to sew small areas and curves.  Also, less will need to be trimmed or clipped later .  For these seams I suggest allowing 1/4″ to 3/8″.
 
2.  Fabric Selection:  Fabric should also be taken into consideration when selecting a seam allowance.  Sheer or transparent fabrics such as chiffon, lace or tulle should be sewn with French seams.  Shirt weight fabrics such as Chambray, Linen, or Silks can be sewn with flat felled seams which is a standard for well made tailored shirts.  RTW Knits such as Jersey, Interlock, Ponte and many novelty knits on the market can be overlocked or sergered with the smallest seam allowances.
 
3.  Seam Finish:  Just as we take fabric selection into consideration in choosing the right type of seam finish, those different seam finishes will require different amounts of seam allowances.  This will all depend on the how much time you want to spend on a seam finish.  If time isn’t a concern, then maybe you want to do French Seams.  If you just want to sew a garment quickly, then maybe serging is the better option.

For the purposes of this series, leaving yourself a moderately generous seam allowance such as the 5/8″ that most pattern companies offer is fine.  I don’t think I would suggest you using any less than 1/2″ seam allowance especially on a princess seam pattern.  The reason being front princess seams need to be notched around the apex and clipped below the bust down towards the waistline.  Anything less than 1/2″ may tend to weaken the seam line.  I touched briefly on the reasons for different amounts of seam allowances, but will keep it simple with suggesting just a basic seam for this semi-fitted shirt.   If you choose to sew all seam allowances as intended on your particular pattern, that’s completely fine, just maintain accuracy. You may feel like you may need a larger seam allowance for your sample fitting in areas that need extra attention, that’s fine also.  You may even feel like trying something new, then at least change the seam allowance around the neckline to experience something different.  You never know, you may find it easier and more efficient!!

Since you’ve taken the time to have yourself measured (Part 1), add ease to those measurements (Part 2), selected a pattern based on those measurements (Part 3) measured (Part 4A) and adjusted your pattern (Part 4B) according to those measurements, you will be good to go on to Part 6:  Cut and Sew a Fitting Sample.  I hope at this point you feel confident in your measuring and excited to sew a sample garment from your new pattern.  Don’t worry if your garment still needs some corrections after you sew your sample.  Please remember that our bodies are dimensional and it’s difficult to navigate those curves other than on a fitting sample.  Corrections are normal and not in any way a sign of failure.  Just remember whenever garments are made for a client, it usually involves 3 fittings.

Don’t forget, I’m planning to conclude this series with a Give Away!!  To qualify for the prize you will need to become a registered follower of my blog and “like” my page on Facebook.

Thank you for taking the time to read Part 5:  Seam Allowances in my pattern fitting series.  I’m happy that so many of you are finding my information helpful and hope you continue on with me.  Thank you also for all the messages, comments and sharing my series links with your sewing groups.  I truly appreciate all your continued support of this series.