Foam mattresses
A construction without springs means foam mattresses do not creak, and that they dampen motion transfer, so two people sleep well on them. They bend, which is why they also suit an adjustable slatted base. They are made from PUR foam, high-resilience foam or memory foam, in heights of roughly 12 to 25 cm. They differ in the density of the material, in firmness and in the number of zones that relieve the shoulders and lower back.
Foam mattresses
A core of one or more foam layers holds its shape without metal springs. Foam mattresses therefore do not pass movement to the other half of the bed and make no sound at all. Their weak point is ventilation, since foam lets air through less readily than a spring unit.
The basis of cheaper models is PUR foam, that is, ordinary polyurethane foam. It is light and affordable but sags sooner. High-resilience foam has a finer structure, returns to shape better and lasts considerably longer. Memory foam responds to body heat and takes on its shape, which spreads pressure, but carries heat away less well. Multi-layer models that combine two or three layers of different firmness are common too.
The quality of foam is indicated above all by its density in kilograms per cubic metre. Values around 25 kg/m³ belong to the entry level, and from 35 kg/m³ upwards the material has a longer service life. Higher density also means a heavier mattress. Height runs from roughly 12 to 25 cm, with lower models suiting children's beds or occasional use.
The surface is often divided into zones, most often five or seven. The zones differ in firmness: they relieve the shoulders and hips while supporting the lower back. Firmness is usually described as soft, medium or firm and is chosen by weight and sleeping position. Side sleepers suit a softer surface, back and front sleepers a firmer one.
Foam mattresses work on both a rigid and an adjustable slatted base, because they bend without damaging the core. Rotate the mattress regularly so head and foot ends swap places, and flip it to the other side on double-sided models. A removable cover with a zip can be washed and extends the lifespan.