Two sofas can look identical in a photo and still differ by ten years in lifespan. The difference is inside: the frame, the support system and the cushions. Retailers do not always list these details, but once you know what to ask for, the product specifications tell you a lot. This guide explains each part and what good, average and poor construction look like.
1. The frame
The frame carries all the weight and takes the stress when people drop onto the seat or sit on the arms.
- Best: kiln-dried hardwood such as oak, ash, maple or beech. Kiln-drying removes moisture, so the wood does not warp or crack later.
- Good: multi-layer plywood (often 7 to 13 layers) combined with hardwood in the stress points. Good plywood is strong and stable.
- Weak: particleboard, fibreboard (MDF) or soft pine used for the whole frame. They are cheaper but can loosen or break under load.
Look at how the frame is joined, too. Corner blocks that are glued and screwed, dowels and double-dowelled joints are signs of good work. Frames that are only stapled together tend to loosen. A long frame warranty (ten years or more) usually indicates the manufacturer trusts the frame.
2. The support system (springs)
- Eight-way hand-tied springs: coil springs tied to each other in eight directions by hand. This is the traditional premium method; it gives even, long-lasting support.
- Sinuous springs (also called S-springs or no-sag springs): zig-zag wires running from front to back. They are used in most mid-range sofas and work well when the wire is heavy-gauge and the springs are closely spaced and linked with clips.
- Webbing: elastic or woven straps stretched across the frame. High-quality elastic webbing is common in modern European designs; cheap webbing sags sooner.
- Pocket springs: individually wrapped coils, either as the main support or inside the seat cushion, for a bouncier, mattress-like feel.
3. The cushions
Cushions decide how the sofa feels on day one and how it feels after a few years.
- Foam density: the most useful number. For seat cushions, look for high-resilience (HR) foam with a density of about 1.8 lb/ft³ (around 29 kg/m³) or higher; 2.5 lb/ft³ (40 kg/m³) and above lasts longer. Low-density foam feels soft in the store but flattens quickly.
- Foam wrapped in fibre or down: a foam core wrapped in polyester fibre or a feather/down blend combines support with a softer surface. It is a good all-round choice.
- Down or feather: very soft and luxurious, but needs daily plumping and loses shape faster.
- Polyester fibre only: cheap and soft at first, but compresses and goes lumpy; mostly suitable for back cushions.
- Pocket-coil cushions: springs inside the cushion, wrapped in foam. They keep their shape well and feel supportive.
Reversible cushions that you can flip and rotate wear more evenly. Removable covers with zips make cleaning easier.
4. Upholstery and tailoring
Check that seams are straight, patterns line up across cushions and panels, and the fabric is pulled evenly without puckers. For fabric, the abrasion rating and cleaning code matter (see our upholstery fabrics guide); for leather, the grade and finish (see leather vs fabric).
5. Legs and base
Legs should be screwed into a solid block or a metal plate in the frame, not just into the upholstery base. Wooden or metal legs are sturdier than plastic. Glides or felt pads protect your floor.
Quick tests in a showroom
- Lift one front corner about 6 inches (15 cm). If the other front leg lifts almost at the same time, the frame is rigid. If it stays down for a while, the frame twists.
- Press on the arms and the back. You should not feel the frame bending or hear creaking.
- Sit down firmly on each seat, including the middle and corner seats. You should not feel the frame or the springs.
- Unzip a cushion if allowed, or ask for the foam density and fill.
- Ask about the warranty for frame, springs and cushions separately.
Questions to ask when buying online
- What is the frame made of, and how are the joints fixed?
- What type of spring system is used?
- What is the seat foam density, and what is the cushion wrapped in?
- Are the cushions reversible and the covers removable?
- What does the warranty cover, and for how long?
- What is the return policy and who pays for return shipping?
If a retailer cannot answer these questions, treat that as information too. For practical buying tips, see where to buy a sofa and our guide on measuring for a sofa.