What happens if you have sloping shoulders? Well, there is good news and there is bad news.
The fashion industry makes clothes and patterns for a “standardized body” and an “average person”. If you happen not to match these averages, you have a bad luck and most of the ready-to-wear garments and regular sewing patterns will not suit you fine.
Having sloping shoulders, you will almost surely see diagonal lines running from the armpits up towards your collar indicting the excess of fabric. At the same time you have diagonal lines running into your underarms from the midsection of the garment indicating that there is not enough room for the sleeve. The more prominent these wrinkles are, the larger correction is needed.
In order to get rid of both issues, you need to increase the shoulder slope of the shirt (to match the natural line of your shoulders) and adjust the armhole
Also on the back you will see some irritating diagonal drag lines running from the armhole to the yoke (and sometimes even up to the shoulder seams). There is no way to make them disappear by pressing, stretching etc. Going one size up or down will also not solve this problem (without creating another fitting issues). A sloping shoulder adjustment is simply needed.
Good news – while making your own garments you can use a pattern constructed for the increased shoulder slope and improve the shoulder fit dramatically.
Bad news – you will probably need to accept these drag lines in commercial clothes and standard patterns. Making shoulder adjustments to purchased garments is in most cases pretty much impossible without scarifying other aspects.
Sloping shoulders quite often go together with rounded back or promonent shoulder blades and arms trusted slightly forward. If that is the case, you may see some fabric tension in the middle part of the yoke and drag lines between the yoke and back neckline. In general, the whole silhouette with sloping shoulders is more round. Therefore very basic, square in form garments are not too flattering here, making you look bigger and misshaped. More tailored clothing will serve you much better.
Note: many commercial garments have one central pleat (or two above each shoulder blade) on the seam joining the yoke and the back – also to disguise some potential shoulder/back fitting issues.
Have a look at the shoulder and sleeve fit of a shirt made from a pattern taking into account sloping shoulders requirements. As the natural angle of shoulders and the pattern are more aligned, the shirt drapes smoothly across the upper chest, without pull or drag lines. A proper shoulder fit is critical to an attractive look of a shirt, makes your garment really presentable. It is worth giving a try.
To sum up: compare the fit of the two shirts on a silhouette with sloping shoulders.
Both garments are the same size, have the same sleeves, but one of them is constructed for a body with a larger shoulder slope.
Please note, that there is nothing wrong with the standard pattern as such. What is not working, is the combination of a standard pattern and a body with a more prominent shoulder slope. Keep that in mind.
On the left side you see the combination of a sloping shoulders silhouette and a standard shoulders pattern. The slope of the shoulders and the pattern are not aligned. Some symptoms might be that the bodice gapes at the top of the shoulder or below the yoke and that the armhole at the side seam is too high (most likely also digging into the armpit).
On the right side you see the combination of a sloping shoulders silhouette and a sloping shoulders pattern. The shoulder slope of the pattern corresponds much better to the natural slope of the shoulders. Thanks to that a “regular” look of the silhouette with sloping shoulders can be achieved.