Trench coats are classics that never go out of style. Don't give away a trench coat that is in good condition just because it no longer fits because of weight gain or loss. Alterations, although time consuming, can be done by the non-professional. All that is need are basic sewing skills, attention to detail and patience.
Checking the Fit
Good fit is a combination of two elements: the garment must be comfortable and look good. Sandra Betzina in her book Fast Fit recommends using the following guidelines to determine whether a piece of clothing fits. These criteria are also helpful in determining how and where to alter the trench coat. Try on the trench coat and check to see that the vertical seams are perpendicular to the floor. Darts---if applicable---should point to an area of fullness, shoulder seams should not pucker, the back should fit smoothly without pulling or buckling, sleeves should not bind or wrinkle across the shoulder cap, the hem should be parallel to the floor and the armholes should not rise when either arm is raised. If any part of the jacket does not meet these criteria, then it needs to be altered.
The trench coat may or may not have a lining. If it does, alterations made to the coat also need to be made to the lining. Carefully cut the seam of the lining to get to the inside of the jacket for the alterations.
Altering a Tight Coat
If the trench coat is too tight, determine where it is too small. If it pulls at the front, see if the buttons could be moved first. Put the jacket on and pin it closed through the buttonholes so that the garment no longer pulls. Buttons should not be moved more than three-eighths of an inch. Mark the new button position with sewing chalk, making sure the new position lines up with the old button position so it will match the buttonhole. If the coat still pulls in front, check the side seams to see if there is enough seam allowance to let them out. If so, carefully remove the seams along the sides, adding the same amount to both sides of the coat by dividing the amount of the increase needed between the two seams. Another way to get more room in front is to reduce the size of the darts, which are used to shape garments. The trench may or may not have them. If it does, turn the coat inside out and carefully remove the stitching on the darts. Adjust with pins, making the darts smaller, dividing the amount of the decrease between the two darts and see if the pulling is relieved. If the trench has a waistline seam, the darts will be located near the waistline. The pulling may be alleviated by opening up the front waist seam along with darts only and resewing them. If the garment pulls across the back shoulders, then the middle seam that runs up the back can be let out and resewn. Check to see that there is enough seam allowance to do this. If the arms or length of the coat too short, check to see if there is enough hem to lengthen them.
Altering a Coat that is Too Large
If the trench is too large, again determine where alterations need to be made. First consider moving the buttons. This is possible if the button does not have to be moved more than three-fourths of an inch from the edge of the coat. If the coat is still too large, the side seams can be taken in. Measure the amount the coat has to be taken in and divide the increase equally between all the seams. The darts can be enlarged in a similar manner. Measure the amount first, then divide the increase between the two darts. For both the side seams and darts, mark the new size for either one, baste and stitch, then remove the old seams. If the arms or coat are too long, hem them up.