Trench Coat

Fashion Academy · Garment anatomy

The Trench Coat

A trench coat is a weather-conscious overcoat defined by its overlapping front and adjustable protective details. This lesson uses the classic double-breasted, belted version to show how those components work together; a trench silhouette alone does not make a fabric waterproof, and modern versions often simplify or reinterpret the original construction.

Black-and-white technical flat of a classic double-breasted trench coat shown from the front and back — Front and back technical flats of a classic trench coat. Select any numbered label to move to its construction note.

Protection, movement and structure

How the trench coat is built

The recognisable details are not random decoration. Each one controls coverage, adjustment, movement or the way the outer fabric handles changing weather.

Collar

The collar frames the neck and can be worn open, turned up or closed more closely against the weather. On a classic trench it is broad enough to balance the lapels and usually contains an upper collar, undercollar and internal support. The undercollar may be cut slightly smaller so the outer edge naturally rolls underneath. Accurate notches, careful clipping and directional pressing are essential: a collar that looks symmetrical on the table can still twist once it is attached to the neckline.

Collar stand

The collar stand is the short inner section that lifts the collar away from the neckline and controls how it rolls around the neck. It may be drafted as a separate piece or incorporated into the collar shape, depending on the pattern. Its curve must match the coat neckline while allowing enough room for layers underneath. Interfacing adds stability, but excessive stiffness can make the collar sit like a rigid band. The stand is also where any throat-closing detail would be positioned on versions that include one.

Lapels

The lapels are the folded front edges created when the coat opens below the collar. Their roll line, width and notch shape establish much of the trench coat’s character. Inside, interfacing and careful pad stitching or fused construction help the lapels turn cleanly rather than lying flat and lifeless. Both sides should mirror one another at the break point where the front begins to roll. Press with control rather than crushing the edge, particularly if the cloth has a soft surface or visible nap.

Epaulettes

Epaulettes are narrow shoulder tabs secured with buttons near the neck. Historically they helped retain equipment straps or indicate rank; in modern trench coats they are mostly a recognisable functional detail. Their length must suit the shoulder width without extending awkwardly beyond the sleeve line. Interfacing keeps them crisp, and the free end needs enough room beneath the button to lie flat. Because they sit high on the garment, uneven placement is immediately obvious when the front and back views are compared.

Raglan sleeves

A raglan sleeve extends into the neckline instead of joining the body at a conventional armhole. The diagonal seams running from the neck towards the underarm create the distinctive shoulder line and allow generous movement over clothing. Front and back sleeve sections are shaped differently, so their markings should never be treated as interchangeable. Matching seam lengths, easing where instructed and pressing over a rounded form prevent ridges. Waterproof or water-resistant versions may also need seam treatment appropriate to the fabric and intended performance.

Gun flap

The gun flap is the extra shield on the upper front, traditionally associated with cushioning equipment and helping rain run away from the chest. It is usually attached into the shoulder, armhole or front seam and may be secured with a button. The flap needs enough structure to remain smooth but should not create a stiff shelf over the bust. Its lower edge must be finished neatly, and its position should cooperate with the lapel and button layout rather than crowding those details.

Double-breasted front

The double-breasted front uses a wide overlap and two visible columns of buttons. One side fastens over the other, while an internal anchor button may support the underlap and stop it dropping. Button spacing controls both visual rhythm and how securely the coat closes across the body. The centre-front lines, not the raw edges, must align correctly when the coat is fastened. Reinforce button positions on the inside, especially in dense fabric, and test the closure over the layers the coat is expected to cover.

Storm shield

The storm shield is the cape-like upper-back layer that encourages rain to shed away from the main back panel. On some trench coats it also covers ventilation openings, allowing air movement without leaving the back directly exposed. Its outer edge needs a clean, flexible finish so it lies close rather than kicking out. The shield should remain level across the back and balanced at both armholes. Extra thickness where it meets the raglan seams can be reduced through thoughtful grading and pressing.

Belt

The self-fabric belt controls the coat’s volume and defines the waist without permanently shaping the body panels. It must be long enough to pass through the buckle with a usable tail, while its width needs to suit the buckle and belt loops. Interfacing or a firm internal tape prevents stretching, particularly in cloth cut partly off grain. Stitching lines should remain straight along the full length. Before finishing the ends, confirm how the belt will be worn, because buckle fastening and knotting require different practical lengths.

Belt loops

Belt loops keep the belt at the intended waist level and stop it sliding down when the coat is open. Their placement should relate to the wearer’s natural waist and remain level around the body. Each loop needs enough internal space for the belt to move without twisting, plus secure attachment that can tolerate repeated pulling. The ends may be inserted into seams or topstitched to the coat. Reinforce them discreetly, but avoid creating a dense lump that becomes visible through the outer fabric.

Buckle

The buckle closes and adjusts the belt, turning a simple fabric strip into a controllable fastening. Its internal width must match the finished belt, otherwise the belt will either bunch or move too freely. A fabric-covered buckle creates a continuous look; metal or resin gives stronger contrast and may add weight. The buckle end of the belt needs secure construction because it carries tension. If eyelets are included, test their spacing and reinforcement on a sample before puncturing the finished belt.

Welt pockets

Welt pockets create narrow, tailored openings at the front hip while hiding the pocket bags inside the coat. The welts must be identical in length and angle, and the opening corners need precise cutting to avoid fraying or small puckers. Pocket bags should be deep enough for practical use and anchored so they do not drag the coat front out of shape. Stabilising the opening before sewing is sensible, especially in fabrics that stretch or unravel easily. Marking and basting pay off here; improvising the cut rarely does.

Cuff straps

Cuff straps wrap around the sleeve near the wrist and adjust the opening with a buckle or button. Tightening them reduces the gap where wind and rain can enter, while visually balancing the belt and epaulettes. The strap length must allow adjustment without leaving an excessive loose tail. Its attachment point should not distort the sleeve when tension is applied. Small components become bulky quickly in coating fabric, so grade seam allowances, choose suitable interfacing and test whether the buckle can move freely before final assembly.

Centre-back seam

The centre-back seam joins the back sections and provides a strong vertical reference for balance. It should hang straight from the storm shield to the vent, even when the belt is fastened. The seam can include subtle shaping, but large fitting changes may pull the grain off course or disturb the vent below. Pressing direction depends on the construction and any waterproofing treatment. At the vent opening, reinforce the point where the seam separates so ordinary movement does not place all the strain on a few stitches.

Back vent

The back vent is the overlapping opening at the lower centre back that gives stride room without leaving a permanent split. Its underlap and overlap must be drafted, pressed and secured in the correct direction so the vent stays closed when the wearer is standing. The top is a stress point and needs reinforcement. Linings require their own allowance and movement fold around the vent; if the lining is pulled too tightly, it can hold the outer coat open or tear during walking.

Hem

The hem finishes the lower edge and gives the long coat its visual weight. A trench hem travels around broad front and back panels, so even a small cutting imbalance becomes noticeable. The allowance may be turned, faced or supported with tape depending on the fabric and lining method. Ease excess fullness at curves rather than forcing it into pleats. Let the coat hang before levelling, then measure from the floor with the belt relaxed; fastening the coat too tightly during marking can change how the panels settle.

A convincing trench coat comes from coordination: the collar rolls cleanly, the overlaps close without strain, the belt sits level and the back still moves freely when the whole coat is fastened.

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