Underlining a coat like this has two major perks: It gives you the chance to really spice it up as your underlining and bias taping will be visible. It also opens up the fabric options you have for the outer fabric as you can hide ugly or scratchy wrong-sides or add weight to a not-quite bulky enough fabric. I think the underlining on my Sewaholic’s Robson Trench Coat is the best part and I wanted to share what I did to make it easy for you too to underline your own trench.
Most of what you’ll be doing is the same as the instructions included with the pattern, so I will just be highlighting what to do differently. The major difference is that you will be finishing the edges of your pieces before sewing the coat together instead of as you go. This means that you don’t have to constantly re-thread your machine if your bias tape is a different color than your coat. This also finishes both edges of each seam so that the seams can be pressed open and two strips of bias tape show for every seam. This gives seams a pleasing symmetry.
Cut your fabric
Interfacing: as instructed EXCEPT 12
Cut from fabric AND underlining: 1,2,3,4,5,12
Cut ONLY fabric NOT underlining: 6,7,8,9,11,13,14,15,16,17
Cut from ONLY underlining NOT fabric: 10
For all pieces that are cut from fabric AND underlining, sew fabric and underlining together at the very edge, WRONG sides together so that the right sides of both fabrics are visible. You can serge them together if you use the utmost caution to not trim off any of the fabric. From here on out, you will treat each doubled piece as one.
Sew seam binding onto all the sides marked in the diagram above, making sure that you are catching both fabrics in your seam. (This is greatly sped-up by using a bias binding foot. For tips, see my tips on how to use a bias binding foot). You don’t need to tape the front seam on either front or facing because that seam is fully hidden. Shoulder seams also end up fully hidden. The seam attaching the sleeve to your jacket body and the pocket are the only pieces that have the bias tape added after construction.
Sew your coat.
1. Interfacing as instructed EXCEPT don’t interace interface Front Facing 12. Instead, I chose to underline it. (It won’t ever be visible, but I wanted the weight of the facing to be consistent with the weight of the rest of the coat.)
2. Sew center back seam. For this seam, and all others like this, instead of pressing to the side and then binding the seams together, press the seam open and topstitch each (already finished) edge down.
3. Sew pockets as instructed. Add bias binding to the raw edge.
4-6. As instructed
7. Finish pocket seams. (Don’t clip as instructed because you have already finished your seams.)
8. Topstitch as instructed. Also topstitch on the other side of seam, holding the pocket and pocket welt out of the way.
9. As instructed.
10. Sew front to back as instructed, with same modifications as step 2.
11. Sew shoulder seams WRONG sides together and press open (the seam will be hidden underneath the flaps and it makes the inside shoulder look prettier). This can also be done on a coat that you aren’t underlining.
12-20. As instructed.
21-22. Sew sleeves as instructed. Use the same modifications as step 2 for the two seams that sew Top Sleeve 4 to Under Sleeve 5. For the seam that attaches the sleeve to the body of the trench, sew as instructed, NOT as modified.
23-26. As instructed.