Sitting on a sofa in a showroom for a few minutes tells you little about how it will feel five years later. A new sofa is almost always comfortable; the differences appear over time, when dips form in the seat and back cushions go flat. The main reason for that change is hidden under the upholstery. Asking about the type and quality of the filling when ordering tells you more about a sofa's lifespan than almost any other question.
Foam: the sofa's main muscle
The seat of most modern sofas is built around polyurethane foam. Its quality is described by two properties:
- Density — how much a cubic metre of foam weighs. The higher the density, the more slowly the material fatigues and the longer it keeps its shape.
- Firmness — how far the foam compresses under pressure. Firm foam gives an upright seat; soft foam gives a sinking-in feeling.
These are not the same thing. Foam can be soft yet dense, or firm yet low in density. Durability is mainly linked to density, while the feeling of comfort comes from firmness. A common problem in cheap sofas is low-density foam: it feels fine for the first months and then collapses where people sit most often.
High-resilience (HR) foam has a different cell structure from standard foam. It recovers its shape faster once the pressure is removed and is the preferred choice for seats in heavy daily use.
Polyester wadding and fibre fill: the soft layer
Polyester wadding and hollow fibre fill are light fillings made from synthetic fibres. They do not replace foam; they complement it:
- A thin layer of wadding over the foam block smooths the upholstery, softens the corners and reduces direct rubbing between fabric and foam.
- Fibre fill in the form of small balls is used in back and scatter cushions. It is light and airy, and plumping the cushion restores its volume.
The weakness of fibre fillings is that they migrate over time. Without internal compartments, the fibre in a back cushion settles to the bottom and the top goes empty. Good cushions therefore have stitched internal channels, and removable covers make it possible to shake them out and restore the shape from time to time.
Spring units
Some sofas have a spring unit beneath the foam. In a connected (Bonnell-type) unit the springs are linked, so pressure spreads to neighbouring points. In a pocket spring unit each spring sits in its own fabric pocket and works only where it is pressed, which means two people sitting side by side disturb each other less.
A spring unit alone does not make a sofa comfortable. It needs foam layers above and below, otherwise the springs can be felt and wear the upholstery. In sofa beds the folding mechanism can also restrict the choice of filling, because the seat has to fold away.
Seat, back and arms are not the same
Each part of a sofa carries a different load, so the filling differs as well:
- The seat takes the most load: dense, resilient foam and, where needed, a spring unit form its core.
- A softer foam or fibre fill in the back gives comfort.
- Arms are used as elbow and head rests and must be firm enough to hold their shape.
- In loose cushions, a foam core wrapped in a fibre layer provides both shape and softness.
Making the filling last longer
Even the best foam tires under a load that falls on the same spot every day. A few simple habits reduce the difference:
- Swap the positions of removable seat cushions from time to time and turn them over so the load is spread evenly.
- Plump fibre-filled cushions once a week to stop the fibre bunching.
- Do not sit on the arms or the top edge of the back; these parts are not designed for that load.
- Keep the sofa away from radiators and strong direct sunlight: heat speeds up the ageing of foam.
What to ask when ordering
- What type and density of foam is used in the seat?
- Is there a layer of wadding over the foam?
- What are the back cushions filled with, and are they divided into compartments?
- Does the frame have a spring unit or elastic webbing?
- Are the covers removable?
Household habits matter too. In a family that often lies on the sofa and where children play on it, a denser seat pays off over the long term. For a guest sofa that is rarely used, softness can take priority.
With made-to-order upholstery, the filling can follow the way your family really sits. Zaferoglu Mebel builds sofas to individual sizes, and its furniture is covered by a warranty of up to five years.
