Sofa Frames & Springs

Learn about high-quality interior sofa construction and its benefits

It goes without saying that good foundations are the most important element for building a home which will last. Likewise, the most important element of a luxury sofa are its foundation—the frame and springs.

A well-made sofa frame enhanced with quality springs will allow your piece to last throughout the years and will provide the kind of sofa support you deserve. A sofa which is made from inferior materials may not have the same longevity.

What’s important to know is that, whilst there are benchmarks for quality sofa construction, the methods and techniques used will be determined largely by the brand and country of manufacture. There is no one way to build a sofa but there are many great ways and that is the goal of buying a luxury sofa.

Hardwood Sofa Frames

A quality frame which provides ample sofa support will be made from solid hardwood.

Hardwoods

Kiln Dried Wood

FCS-Certified Wood

This type of wood is another industry standard and the most responsible and sustainable approach to wood furniture construction. Producers of FCS-certified woods adhere to the Forest Stewardship Council’s 10 rules which include “maintain[ing] or enhanc[ing] the social and economic wellbeing of workers” and “maintain[ing], conserv[ing] and/or restor[ing] ecosystem services and environmental values” of their forests as well as striving to “avoid, repair or mitigate negative environmental impacts”.

Popular Woods

Premium Engineered Hardwoods & Plywoods

These types of wood can also work well for sofa frames, however, care should be taken to discover the lengths to which the manufacturer has gone to produce the strongest and best quality wood and where this will be used. Sometimes, even in luxury sofa manufacturing, composite woods or softwoods are used for sofa frames in non-stress areas. This is acceptable if affixed properly because these areas do not take weight.

Softwoods & Composite Woods

Climate Considerations For Sofa Frames & Lacquers

Not only do furniture makers pay close attention to which type of wood they use for strength reasons, they also bear in mind the climate the sofa will be in. Outdoor conditions and weather are important, as are indoor conditions such as underfloor heating and the proximity of the sofa to radiators or heating vents.

Choosing a solid piece is just the first step of making a sofa frame; the sofa finish is the second. We know that there are certain woods which work better in specific environments and this goes for stains and lacquers too. For cold environments, lacquer is best. Warmer environments call for wood oils because these penetrate the timber during sudden temperature change; lacquer would crack in this instance.

The Joinery

The joinery used for a sofa frame is of the utmost importance and can make or break a sofa (quite literally). Carpentry joints—in particular mortise and tenon and dovetail—are some of the most secure sofa construction techniques and may be found in the works of more traditional furniture makers. Mortise and tenon joints are one example of high quality sofa joints and will likely never be found in cheaper models. In more modern practices, a combination of glued, screwed and dowelled is common as is glued and screwed.

Legs and arms which are integral to the sofa’s frame are preferable but, if not appropriate, these should be secured using screws, dowels, brackets, wooden corner blocks or another suitable joinery fixture.

Joinery Glues

Joinery glues have been an important part of sofa construction but, whilst animal glues were used in the past, synthetic adhesives are used nowadays. “The rapid development of synthetic adhesives over the last few decades has virtually eliminated the natural animal glues used for centuries,” the Furniture Industry Research Association explains on its website’s knowledge hub.

Sofa frames which are only glued or held together using nails or staples will perhaps last for a little while but are less likely to have the same longevity as a sofa made with more thorough carpentry joints.

A good sofa manufacturer will be able to provide you with all relevant information on the construction of a sofa’s frame.

The Base Support

There is more to sofa parts than the frame. Once a sofa frame has been constructed, the next step is to prepare a base (also called a sofa deck) on which the spring support, upholstery and cushions can be applied. This foundational sofa support consists of a series of durable straps woven close together, stretched using an upholstery or webbing stretcher tool and affixed to the frame. This solid flat plane becomes the base of the sofa seat. Three of the most commonly used materials are: jute, polypropylene and rubber.

Jute Webbing

Jute webbing was one of the original upholstery webbings and is sometimes used, today, by furniture workshops which employ traditional techniques. Made from vegetable fibres, jute comes in many weave varieties but a tight jute will be the strongest and most resilient for upholstery.

Polypropylene & Polyethylene Webbing

Prized for their durability and resistance (including weather and mildew resistance), polypropylene and polyethylene are made from strong plastic compounds with high breaking points—perfect for sofas. Many modern furniture makers have opted for these webbings in their sofa construction.

Rubber Webbing

Rubber webbing has an elastic characteristic so provides a bouncier seat. This has become one of the most popular options in sofa construction and is attached using staples. Brand names like Pirelli are leaders in the field of rubber webbing and guarantee high quality and longevity.

The Spring System

Sofa springs are one of the most important factors of a sofa’s comfort and should be of the highest quality for the most comfortable, supportive and long-lasting piece. Think of it - aside from a bed (which also uses spring systems), a sofa is probably one of the most-used furniture pieces, hosting many people and a lot of weight for extended periods of time. A good support system is vital.

Most furniture makers agree that there is no one best spring system, although there are certainly some methods which are superior to others. Knowing this, here are the four main types of upholstery springs and foundation: eight-way hand-tied or hand-knotted, S or sinuous springs, pocket spring and web suspension.

Eight-Way Hand-Tied Springs

The eight-way hand-tied method - the most traditional coil spring suspension - results in one of the most comfortable sofas. Also known as a coil sprung system, it consists of individual hourglass-shaped couch springs of varying thicknesses being individually affixed to the webbed seat base. This is done by hand and the knots are tied in an eight-way configuration - front to back, left to right and diagonally in both directions.

Fixing the coil springs individually provides the most tailored support because each can respond, independently, to differing weight pressures. This offers support and distributes weight correctly.

Serpentine Springs

Also known as sinuous springs, S-springs or zig zag springs, serpentine springs are flat and feature repeating, zig zag curves. These wires are attached to the sofa deck from front to back.

These springs come in various thicknesses depending on the desirable comfort level, i.e. higher and firmer or lower and softer, and straight cross wires are placed at right angles to the serpentine springs to provide further support. Springs with tighter curves and with more turns provide more strength as do plentiful wires placed close enough together so that the sofa has an even and supportive seat surface.

Pocket Spring Cushion Units

Pocket sprung units are made up of multiple coils, individually wrapped in a lightweight fabric and bound together at the top and bottom with metal rings. These pocket spring systems are not as desirable as other spring systems because they are usually made of inferior materials and can weaken and wear out. They are known for being uncomfortable and can be noisy too. Pocket spring units would never be recommended for high-end upholstery.

Buyer beware - some sofa manufacturers will claim that their sofas are eight-way tied because they are spring-based when, in reality, they are pocket sprung sofas.

Web Suspension

Upholstery webbing is the simplest form of sofa deck and consists solely of a webbed base without any additional spring system support which means that is doesn't provide responsive support. Although rarer, web suspension works well in some instances and was used prevalently in Mid-century design, for example. Webbing alone is a popular option for slimmed down modern sofas because it doesn’t require the same depth as spring systems.

If used alone, it should be of a high enough quality to ensure resiliency and fitted correctly so as to not cut through any surrounding foam.

Finishing Up

After the frame is sprung or webbed, there are multiple layers to be applied before a final lining fabric can be attached to the seat deck. Whilst practices vary, these can include an initial covering (called scrim), initial foam layers and thin wadding. Scrim is usually made from a cruder fabric such as jute, hessian or calico and simply acts as a barrier between the spring system or webbing and upper layers and keeps each stage of the process contained.

This would also be the stage when the bottom cloth or dust cover is applied which is the material underneath sofa frames which conceals internal workings and prevents the area from becoming dusty. Further proof that every single area of a sofa is carefully considered.

Here at LuxDeco, we are committed to helping customers around the world discover the sofa of their dreams. If you would like help designing or choosing your luxury sofa, contact our team at [email protected] or +44 (0)20 3322 8665.

Discover More

Continue on your sofa journey and learn more about the craftsmanship and care that goes into the production of our luxury sofas.

Types of Sofa Cushions