sway back alterations – my analysis

In my last post I mentioned that I did a sway back adjustment on my white tank top, and some of you asked how to do this on a back where there are no seams. Here I’ll show what I did, but I’ll cover some theory too for the geeks amongst us!

My alteration didn’t fix my wrinkles completely, so after lots of thought and reading I came to a few other conclusions that I’ll share. I’m as guilty as anyone here, but I think there are a lot of misdiagnosed sway backs, and sway back alterations are often done unnecessarily, and done where other alterations may be more effective – wrinkles at the back waistline are not only caused by a sway back!

So What Exactly is a Sway Back?

A sway back is where the natural inward curve of the spine at the back waist is exaggerated.  It could be due to the backward tilt of the thorax, or the forward tilt of the pelvis, or a bit of both.

It causes the vertical distance between the bustline and the hipline to be shorter than normal at the centre back (CB).  The side seam remains of normal vertical length:

How does this affect the fit of garments?

Essentially the centre back length (CBL) of the garment appears too long.  The appearance depends on whether the garment is fitted or loose:

  • In a fitted garment, horizontal wrinkles will form across the back waistline.  With a sway back these wrinkles will be most pronounced at the CB, and they will stop short of the side seam which remains flat.
  • Looser garments may balloon above the back waist, or the hipline/hemline falls longer at the centre back while the side seams swing forward.

Other issues easily confused with a sway back:

Browsing online, I have seen the following fit issues frequently confused with a sway back problem:

  • A short (high) waistline – on a fitted garment this causes horizontal wrinkles that extend into the side seams and front bodice.  To fix this the whole bodice needs shortening, not just the CB.
  • A large back high hip, or prominent buttocks – tightness in these areas causes the fabric to “ride up”.  The garment needs to be made wider in these areas to prevent ride up.
  • An erect upper back – excess fabric length in the upper back may drop down to the waist area, and to prevent this the complete upper back requires shortening.
  • A prominent front or bust – insufficient fabric length in the upper front may pull up the front waist, causing drag lines towards the back waist.  The front needs to be lengthened to solve this, and often widened also.
  • Looseness at the back waistline due to insufficient waistline reduction.  The vertical dart shaping should be increased or sculpted for a closer fit.
  • Diagonal wrinkles – these can be caused by strain from another direction, eg a prominent bust, or overshaped side seams.  Waist reduction should be relatively evenly spaced around the body, not just at the side seams, to prevent these.

However a sway back can exist in conjunction with these fit issues.  I also have a short waist, erect back, and a large back high hip.  On my tank top, all these issues were contributing to wrinkles across the back waistline.  In fact, a sway back was probably the least of my worries!

I recommend fixing these other problems before determining whether a sway back adjustment is required – it may not be necessary after all!

So – how do we adjust for a sway back if it is necessary?

Simple – we reduce the centre back length!  The side seam remains unchanged.

First try the garment on and pin out the excess fabric in a horizontal tuck, beginning at the CB and tapering to zero at the side seams:

Measure the total length that you need to reduce – it is usually about 1 – 1.5cm (1/2″).  If you need to reduce much more than this, I would definitely check that some of the fit issues mentioned above are not present.

In this example my folded tuck measures 6mm, so I need to reduce the CBL by 12mm in total.

The pattern alteration undertaken depends on whether the garment has a waistline seam, a CB seam or no seams.

For skirts or trousers:

Scoop out the upper edge of the back – this corrects the CB waist to hip measurement:

Before you cut, fold the darts closed so they maintain their correct shape:

At the CB, ensure the waistline and CB seam remain square:

For garments with a horizontal waistline seam:

Scoop out the bodice panel as well as the skirt, enough on each so the waistline seam remains in the correct anatomical position.  Fold the darts closed before cutting and square the waistline at the CB like above:

For garments with a CB seam and no horizontal waistline seam:

Slash along the waistline and overlap your pattern at the CB seam the same width as your horizontal tuck:

Smooth the lines of the CB and side seams (blue dotted line):

The grainline will need to be redrawn – here I have maintained the grainline of the skirt so that it hangs correctly, for a top I would probably maintain the grainline of the bodice:

For garments with no back seams:

On the half-pattern, slash and overlap your pattern the width of your horizontal tuck as above.

Redraw the CB fold between the CB neck and CB hem:

Square the hem to the centre back:

Trace around the side seam to the CB neck.  The CB neck should be square to your new CB fold if it previously was:

You can see the old outline in pencil, and that the back waistline is now larger.  To alter this, match the underarm point and side hem points like so:

And redraw the new side seam shaping (line with a tick):

This method is basically what I use for seamless backs, and is the same as that described in Aldrich.  But see how it also increases the back bodice width?  To prevent this I usually redraw the side seam shaping from the hem directly to the shoulder point instead.

There is also another method I discovered, documented here.  This produces a very similar result to mine, but I find the shoulder angle becomes too square for my liking.  You might like to try it out to see what you think though.

More for pattern geeks:

If you study the end result of these last two methods for a seamless back (my modified Aldrich and the online one), you will notice that the pattern below the back armhole is actually unchanged in shape.  All the change occurs in the shoulder and neck region, and the excess centre back length is effectively being eliminated from the top.  This surprising (to me) revelation led me to discover an even quicker way – my adjustment is the equivalent of simply changing the angle of the shoulder and back neck to the rest of the pattern!

Here’s how – draw right around your pattern from hem to shoulder point.  Then pivoting at the shoulder point, swing the CB neck point downwards by your required adjustment (ie 12mm) and then square the CB neck to the CB fold:

Done – you end up with exactly the same result, only more quickly!

I am really interested in hearing your feedback and experiences with sway back alterations too.  What I do works for me – but I know we are all different shapes and sizes, so please comment and criticise as you see fit – pun intended!  I think a lot of instructions are vague and confusing, and I want to compile a clear summary for everyone’s reference, so do ask if I have overlooked something or you have a query. 

Let the discussion begin!

~ Sherry

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Designer, Patternmaker, Blogger Of All Things Sewing. Follow as I share projects, patterns, and my favourite tricks of the trade.

88 thoughts on “sway back alterations – my analysis

  1. Thank you so much for detailed tutorial on Sway Back.I have a sway back and since i draft my own patterns, i take this into account while drafting.I am sure this will quite useful to lot of sewing enthusiasts out there.


  2. This is very interesting, Sherry. I usually just add a CB seam, even to tee shirt – type patterns, if the bodice back would normally be cut on the fold.

    I am going to try your alternative adjustment and keep the CB fold next time. Thanks!


  3. Thank You for the sharing this information, especially the part on lowering the CB neckline. I have a combination of fitting issues, the biggest is my swayback and slope shoulders and wide hips. My CB is not straight, it has a curve, I made a muslin and the fit in the back is great. In you examples the CB is straight? A person with a swayback their CB pattern should not straight? I am not sure, what do you think? Again thanks for posting such detailed information.


  4. I have to say, I found that all rather fascinating!! I have puzzled this out in my head and came to some of the same conclusions on my own, but this information breaks it down SO simply!! Thank you!


  5. I think that your way obviously works for you but could put the swayback alteration in the wrong place for some people (me, for instance). There are a lot of very neat pdfs on pattern alterations such as swayback available for free here https://agrilifebookstore.org/publications_search.cfm. There's a Threads article on fitting the back generally here http://www.taunton.com/threads/pages/t00103.asp. And a REALLY interesting and different way of doing it here: http://www.fitthat.com/swayback.htm.

    I personally have been cutting my swayback alteration in at three inches below the waist and then I was, if you like, reversing the cut by adding the material back in again at 8 inches below the waist to allow for my generous rear, instead of adding the length at the hem as you suggest.

    I now think (after looking at the diagram in the last link i gave you above) that what i was doing was putting the hip width back in the right place (If you think about it, a swayback alteration doesn't only shorten the back. Since the waistbone's connected to the backbone and the backbone's connected to the hipbone, etc…LOL), it also can also raise the hipline of your skirt/trousers etc above where it should be and that can throw other things out (esp the crotch of pants). So you either need to add it back in where it should be, or take it out in a different way. I think the last diagram is clever for that reason (but haven't got a dress planned to try it out at the moment).

    Sorry this is so long but we share a “fitting interest,” I think! Of course, people who have a swayback without the bodacious rump don't need to (and shouldn't) add any length back in.


    Liked by 1 person

  6. Thanks Sherry – I have not had these issues yet as I have not attempted a sway back 't' – I am going to try this and see how I fair with the pattern and if I can alter as you did, if required. Your instructions are so clear – you have done a fantastic job explaining the problem and solution. I learn something everyday from sewing – it's great.


  7. I also have a small sway back but it pales in comparison to the rest of my fitting issues so I have ignored it until now. I would love to give your method a try as I do find the fabric pooling at the back annoying.


  8. Thank you for “the most useful post of the month”!! Will use it to diagnose why my tshirts ride up at the back. No wrinkling, just gradual creep.


  9. This is fantastic, thanks so much! I have a problem with a sway back and found it hard to find information that explains clearly how to adjust your patterns.


  10. Really great, Sherry! Makes me wonder what other fit issues are contributing to my “sway back”, since the puddling I have is typically more than 12mm or so. Short/high waist is one, but one that I'm usually pretty good about (or even too aggressive about) fixing. How do you recognize an erect upper back? My daughter definitely has the large deriere catching, but I don't think that's one of my problems… hrmm.

    Liked by 2 people

  11. My biggest problem when it comes to fitting issues is that dresses and tops always always gape at the back neck. When I make a muslin and notice the gaping, I usually just add a dart but honestly I don´t think thats the right thing to do. (I think I have a forward neck. But the gaping is so badly that I can´t believe its just from that). Are there any tips you can share about this?
    greetings from germany!


  12. ~alethia – we all have a natural curve in our back whether we are sway or not, so there is no reason the CB seam has to be curved for a sway back. The adjustment reduces excess fabric in the vertical direction only, and CB shaping reduces excess fabric in the horizontal direction, similar to a waist dart. It is trickier when other fit issues are present – I'd start at the top and work down.
    ~tanitisis – you're right large derierre ain't one of your problems! An erect upper back is straight, as opposed to hunched, so it can be shorter than usual.
    ~Chrissy – I can't help too much without seeing pics, but if the dart solves the problem that's great! Look at the shoulder seam too – unpick it and see if you can arrange the neck to sit flatter – the fabric will tell you where it wants to go!

    Liked by 1 person

  13. Wow, thank you. I get those gathers with tops and dresses and it had me puzzled because I thought it wasn't a sway back issue as it never occurs with my skirts. I love that you have listed some other issues other than a swayback for the puddles. Now I can investigate some more.


  14. Sherry, this is really useful, thank you! I've only ever amended my projects for my sway back when there was a back seam involved, and all I did was take the fabric in at the fitting stage. It's great to tips for different types of garments and I'm trying to get better at adjusting patterns so this is brilliant!


  15. I have puzzled and puzzled over whether there is any difference in the fix for a sway back vs. a back high hip. As you describe, you shorten the distance to the back waist. So it sounds like that causes the back hip shaping to sit higher? And as the back hip shaping curves outward, that same fix would solve the back high hip problem. So is there a difference between the fixes?

    Thank you! Love theory.


  16. ~fruitbat – the distance to the back waist is shortened only enough to eliminate the wrinkles, if it causes the back hip shaping to sit higher then it is shortened too much. If the back high hip is large, width needs to be added at that level – princess seams are useful here! The fixes are different in that sway back is a length adjustment, and large high hip is a width adjustment. Hope that helps!


  17. This is a fantastic explanation and very clear diagrams! Definitely bookmarked for future reference. Thanks for putting it all together! I liked the section on things that AREN'T swayback issues too. It's easy to misdiagnose your fitting problems!


  18. ~Hatty – thanks for your great comment – sorry it was late posting, it went into the spam inbox, maybe the links and being anonymous caused that! I couldn't find the first two, but just want to note that the fitthat link is the same one that I referred to above.
    I saw some examples of making the adjustment below the waist online, and if that's where the wrinkles are occurring it makes sense to do it there. I also like your idea of adding the length back in over the buttock if you have a generous one – just like we do on the front for a generous bust – as it would help to keep the side seams vertical. Do you add the same amount in so the overall CB length does not change?


  19. Sherry, I do add the same amount back in, but to be frank I am not as 'exact' as you. I have never pinned out the exact amount or muslined any fitting. I always kind of wing it with adjustments on the paper pattern (I do measure that precisely), and if it's not quite right, reduce or increase the adjustment on the next garment. I hate muslining!

    So, with this SBA, I do just add it back over my rear (but strictly speaking I am doing two adjustments – SB and “full posterior” or whatever). I did it because the first time I did the swayback alteration (on a tunic without a centre back seam (as you point out you do not need a centre back seam to do SBA), it got rid of the pooling, and I was thrilled to bits, but I noticed that the back was short by approximately what i had taken out! I don't have a hugely bodacious rear end, and I think it's just coincidence that my two adjustments are roughly equal. And I am not SUPER fussy about exact fit. I just don't like the pooling at my lower back that I always get in RTW. The standard I aim for is “better than RTW”, not actually couture! Anyway, your way is less slapdash than mine.



  20. Just stumbled on this. I have been wondering for awhile if I have sway back; looked around for definition or diagnostic fitting problems. Finally, you have it all in one place here!!! Can't thank you enough. (I think I have erect/military posture and fuller bust, but no sway back.) Great to see all the possible alterations laid out so well too. Congratulations on this very helpful work. Linda


  21. Thank you so much for this great information. I am an experienced sewer ( well I've been trying hard for for about 40 years!) and have regularly done a sway back adjustment but not quite got it right! After reading your wonderful article I now realise that at barely 5'3″ with a high hip I need to take approx 1″ from the waist area front and back! My lowest rib is only 1 1/2″ from the hip bone. Am I on the right track?


  22. I've been sewing and (of course) wearing clothing forever. I just realized that this is an adjustment I should have been making for years. When I look at myself in the mirror I don't see the sway back but all of my garments leave a puddle of fabric at my lower back. I just made a jean jacket and was thrilled with the final result until I saw the back. If you want to offer an opinion see the link here http://picasaweb.google.com/117500109565780575528/JalieJeanJacket2320#5565562042252822114.
    I can always see the problem with the garment but rarely can I diagnose and solve it. I think your techniques may work for me. Thanks a million!


  23. Hi Claire – Most patterns are designed for the average height of 5'6″, so at 3″ shorter it is likely that you need to shorten the whole bodice. It will help to check your nape to waist, and neck point to front waist measurements, against the pattern sizing. Glad to have helped!


  24. I love dress making, which I have learnt to do in the last few years, I also had Sway back (or 'Lordosis') so made lots of skirts with this adjustment…but I no longer have sway back, so need to make a load of new stuff without the adjustment – my skirts with the adjustment look very odd on me now – hem not straight! I didn't realise you could actually eliminate Lordosis, but I heard of a treatment called 'Myofascial Release' – kind of like a type of deep massage…after a couple of treatments my sway back was gone…I couldn't believe it!! The treatment can also correct Scoliosis too. Quite nice to have one less alteration to do 😀 X


  25. This is the most comprehensive resouce I've found! Thank you so much! I do have a question. I have multiple fitting issues and as a novice, I am getting overwhelmed. I have a round upper back, forward shoulders, sway back, small waist and a huge rump (it's both high and wide. How do I adjust for the sway back and a bubble butt?


  26. NuJoi – keep in mind alterations are horizontal/length related, or vertical/width related, or a bit of both. I find this really helps when dealing with multiple issues. Also try to deal with one at a time, and work from the top down, fitting length in each area before width. A prominent seat may need width and length adjustments, similar to an FBA. Hatty's comments might help too!


  27. This is a great post! I am working on Vogue1218, and have made it fitted but not as tight as shown, trying to keep it office approriate. I made a sloper (cotton), petit altered it, and the garment in a stable double knit. The back has two parts. The lower part is the poblem. I get diagonal lines from the upper end pointing inward towards the zipper just above waist level. Is this a sway back problem? Any ideas to fix the dress vs adjusting the pattern?


  28. ~Sam – it could be a sway back problem, where the excess fabric is transferred to the bottom of the zip. Or it could be that the fabric has stretched when sewing in the zip.


  29. Sherry, thank you so much for this post. I have drafted a leotard patern and wondered how to get rid of a puddling of fabric in the small of the back without the need to add a CB seam (the side seams and the front of the leotard are fine). I am going to try your suggestion tomorrow.


  30. I love this post so much. I do have one thing to add… I did a mock up following your instructions and compared it to the original back sloper and I found that the shape remained unchanged below the armhole along the side seam and hem, and the CB, neck, shoulder and armhole are slightly different. In my experiment the shortcut method pivot point would actually at the bottom of the armhole and would necessitate redrawing the CB as well as the neck shoulder and armhole. Nice trick that I will definitely be trying out!


  31. Hello. I just did a google search on fitting a swayback and discovered your blog. Thank you so much for this interesting post! I really appreciate your clear photos and excellently written text to go with it. I really look forward to browsing through the rest of your blog. Thank you! Best regards, Rachel in Singapore


  32. Thank you for this analysis! I have bookmarked it for easy reference – and I reference it often. I've also shared this link with others. It will definitely help those of us looking for great fit. And by the way, I have the same issues that you do. So thanks again.


  33. Thank you for your wonderful instructions regarding pattern alterations for sway backs. I have a sway back as well as square shoulders so you information is exceptionally helpful. The visuals and notes were especially beneficial, so that I could clearly see the steps you took in correcting your alterations. I look forward to your other technique guides.


  34. Thank you! My daughter has a horizontal wrinkle in the lining for her prom dress, which is fitted. This gives me some ideas to try to get the dratted thing to go away (previous attempts to just add more room at the side seams have resulted in more room, but the same wrinkle). I'd swear that it was off-grain to hang so crooked, except that I spent probably two hours when I was cutting out the 11 bodice pieces to make sure that it was on-grain.


  35. Glad there are other pattern geeks out there!! Great instructions. I would do it the same way (Ive been drafting my own patterns for years and am always looking to learn more!). Just descovered your site and loving it. Thankyou for sharing your wealth of knowledge in such an easily understood clear way.
    From another kiwi..


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