Coil Spring Installation with Jute Webbing Base

Coil Spring Installation with Jute Webbing Base

Eight-way hand-tied coil springs remain the benchmark of quality upholstery seating. When done correctly, they distribute weight evenly, resist sagging, and outlast most foam-only alternatives by decades. This lesson walks you through every stage: planning, webbing, sewing, and tying.

Why Eight-Way Hand-Tying Matters

A coil spring that is only tied front-to-back and side-to-side can twist under load. Adding the two diagonal directions—four pairs of rows total, eight ties per spring—locks each coil in place so it compresses straight down rather than tilting. That consistent motion is what gives a hand-tied seat its characteristic firm, even feel. Employers and certification examiners for both the Custom Tailors & Designers Association credential and the Marine Fabricators Association MFC credential recognize this technique as a mark of craftsmanship.

Spring Selection and Layout Planning

Before you touch a spring, calculate the correct spring height:

> Spring height = rail depth − desired finished seat height (above the rail top)

For example, if the seat rail depth (the distance from the top of the rail to the bottom of the frame opening) is 5 inches and you want the finished seat cushion surface to sit 2 inches above the rail top, you need a 3-inch spring height—but you must also account for compression and the thickness of the burlap or spring cover that goes on top. A general rule used in the trade is to select a spring whose free height is roughly 1 inch taller than the calculated gap, so the spring has slight preload when tied down.

Spring gauge (wire diameter) should match the seat's expected load. Heavier-gauge wire resists compression more; lighter gauge is appropriate for accent chairs with light use. Standard seat springs are typically available in gauges ranging from 9 to 12; heavier numbers indicate thinner wire.

Draw a full-size paper template of the seat opening. Mark the rail positions. Place springs in a grid, keeping them at least 1 inch from any rail and spaced evenly. A typical dining-chair seat may hold four springs in a 2×2 grid; a sofa seat section may use nine or more.

Webbing Base Installation

Heavy jute webbing—3½ inches wide, 72 oz weight—is the foundation. Lighter webbing will stretch or tear under repeated load.

1. Fold the first strip back about 1 inch and tack or staple it to the front rail. Use enough fasteners to hold the fold flat.

2. Pull the strip across the frame using a webbing stretcher. The stretcher lets you tension the webbing without straining your hands and ensures consistent tautness across all strips. Webbing that sags before the springs are even attached will sag much more under load.

3. Tack or staple the far end, fold, and secure as on the first side.

4. Weave the cross strips over and under the lengthwise strips in an interlocking pattern. This adds rigidity and distributes load in two directions.

5. Check that the finished web base has no give greater than about ½ inch when pressed firmly in the center.

Safety note: Keep fingers clear of the staple gun muzzle at all times. Use a tack hammer carefully—strike the tack head squarely to avoid glancing blows that can drive a tack into a finger. Wear safety glasses whenever you are driving fasteners overhead or at an awkward angle.

Sewing Springs to the Webbing

Each spring must be sewn to the webbing at three or four points around its base coil. Use a 5-inch curved upholstery needle and a strong synthetic twine (not spring-tying twine—this is lighter sewing twine).

• Push the needle up through the webbing just inside the base coil wire.
• Loop the twine over the coil wire and back down through the webbing.
• Tie off with a slip knot or square knot pulled tight against the webbing.
• Space the stitching points evenly around the coil.

An unsewn spring will walk sideways under load, ruining your tie work and eventually breaking through the webbing. Keep the spring plumb—use a small square if needed—before cinching the final stitch.

Eight-Way Hand-Tying Sequence

Spring-tying twine (sisal or polyester) is stiffer and stronger than sewing twine. Cut lengths generously—short lengths force awkward knots that slip.

Tying order:

1. Front to back — run a line from the rear rail, tie each spring in the row, anchor at the front rail.

2. Side to side — run lines across the frame.

3. Diagonal left-to-right

4. Diagonal right-to-left

At each rail, drive a tack or staple to anchor the twine before beginning the row, then double-knot the end after the last spring. At each spring, use a clove hitch or the traditional upholsterer's slip knot at the point where the twine crosses the top coil wire. The knot must grip the wire—not slide along it.

After all eight directions are tied, lay a steel straightedge across the spring tops. No spring top should deviate more than ¼ inch above or below the plane of the deck. If a spring is high, slightly loosen its diagonal ties and re-knot. If a spring is low, you may need to re-sew it to the webbing at a slightly higher position—a situation that is easier to prevent by careful initial spring selection.

Final Check and Safety

Press each spring by hand to confirm the knots do not slip. A slipping knot means the spring will migrate under normal use. Instructor verification before any burlap or padding is applied is mandatory—errors hidden under padding cause callbacks that damage your professional reputation.

Always work on a stable bench. Coil springs under tension can snap back; keep your face clear when releasing tension from a tied row. Dispose of cut twine scraps immediately to prevent tripping.