Foam density sofa specification
A practical guide to foam density sofa specification: what to check on site, what a photograph cannot establish, and what to write in your purchase specification.
Foam density is the specification most often written incorrectly and most often quietly reduced. It is also one of the few furniture attributes that both buyers and consumers can feel within a year.
What density means
Density is mass per unit volume, expressed in kg/m³ or lb/ft³. It is not the same as hardness and not the same as resilience. Two foams of equal density can behave very differently.
| Application | Typical requirement |
|---|---|
| Residential seat cushions | ≥35 kg/m³ |
| Commercial and contract seating | ≥45 kg/m³ |
| Back cushions and throw pillows | Lower — 22 to 28 kg/m³ is normal |
| Armrest and bolster filling | HDPE beads, not foam |
How it is measured
By cube-cut sampling. A cut section of the foam is weighed and its volume measured. Density is mass divided by volume.
Where a finished cushion cannot be cut without destroying it, the check moves to the foam block before assembly, or a witness sample is cut alongside the production run. A density certificate without a sampled witness is weaker evidence.
Why it collapses
A 28 kg/m³ foam used for a seat cushion will feel acceptable in the showroom. After a year of daily use it compresses to a depth that no longer supports the sitter, and the cover develops folds that cannot be recovered.
That failure is visible in a photo — if you know to look for it, and if you press the cushion rather than photograph it.
What to write in the specification
"Seat cushion foam density ≥35 kg/m³ residential / ≥45 kg/m³ contract, measured by cube-cut sampling. Three points per sampled unit at minimum; six points at full verification. Readings outside ±10 per cent of the specified value are a finding."
sofa verification scope sets out where this sits in a sofa verification.
Common questions
Can I verify goods without sending anyone to the factory?
Partially. A remote photo review can identify gross problems but cannot establish count, dimensions, materials or physical performance. Those require someone on site.
Do laboratory reports replace on-site inspection?
No. They answer different questions. A laboratory report tells you whether a product meets a standard. An inspection tells you whether these goods match what you ordered.
What should my purchase specification contain?
Model and quantity, dimensions with tolerance, materials named rather than described generically, colour standard with a grey scale value, and any standard the goods must meet.
Verifying a furniture order?
We check your goods at the factory against your PI, your agreed specification and your approved sample. Three levels, published prices, report within 24 hours.