Retail suits can be as good or bad as the brand that manufactures them. Below are a few main features of retail suits that sets them apart from custom garments.
The main aspect of Off The Peg suits is that they’re produced en mass for eventual retail, as opposed to on the request of a client. So the garment exists before your desire for it, meaning that desire must be created through marketing. I think that’s all I’ll say on the topic for this post.
Off-the-peg garments are made from to a pre-drawn pattern, which is graded into the different sizes being produced. Short cuts in grading can leave very large or very small sizes bordering on the absurd (like the shoulders of large shirts hanging down to the elbow). This has gotten worse as global fashion houses try to standardize their fits at the same time as marketing to physically variable people. The outsourcing of most of the grading and production processes hasn’t helped either, and today the sizing (and to a certain extent grading) systems are in complete free fall.
The suit form is achieved with under layers of stiff fabric. Expensive suits use horse-hair canvas attached by hand, while cheaper suits glue thick woven cotton into place.
One massive disadvantage of using glue is that the suit becomes rather rigid, limiting the amount of movement without the suit bending out of shape. Horsehair, on the other hand, allows movement where it’s needed, and limits it where structure is important.
Another (more problematic) problem is that the glue degrades over time, leaving you with bubbles. This process is sped up by strain (simply wearing your suit) as well as moisture from sweat and the environment. Even without these factors the very best glue wont last forever, and there’s no way of fixing the bubbling once it starts.
Seam allowance is the distance between the edge of the fabric and where it’s sewn. It’s a subtle play between too much seam allowance which would warp the final garment, and too little which will cause unraveling.
The broader the seam allowance (custom garments are 1cm to 2,5cm), the sturdier the seam, and the more it can be adjusted outwards to accommodate weight gain. Though the narrower the seam allowance (Off the Peg garments can be as little as 3mm) the more garment you can cut from a length of fabric, and the easier it is to join the seams accurately.
If you’re going off the peg look for a floating chest piece and a good fit in the shoulders, the rest your tailor can sort out for you.