Sofa Bed Mattress Types: Foam vs Open Sprung vs Pocket Sprung (UK)
Two sofa beds can look identical in photos and sleep like different decades: the difference is the mattress inside. It decides whether your guests ask to stay another night or quietly book a hotel. This guide from Sofa Bed Expert (sofabedexpert.co.uk) explains the three mattress types found in UK sofa beds, foam, open sprung and pocket sprung, what foam density numbers like 50 kg/m³ actually mean, and how to read a product page so you never buy a bad night's sleep by accident.
Short version: foam-only mattresses suit occasional guests, open (zigzag or bonnell) springs are a step up, and pocket sprung mattresses are the standard for every-night sleeping because each spring supports you independently. Every Sofa Bed Expert sofa bed has a pocket sprung mattress and pocket sprung seats as standard.
Key takeaways
- Foam-only folding mattresses are the budget option: fine for the odd guest, but low-density foam can flatten with regular use.
- Pocket sprung is the every-night standard: individual fabric-wrapped springs support hips and shoulders independently, like a quality standalone bed.
- Foam quality is measured in density: our high-resilience foam is rated 50 kg/m³, which resists sagging far longer than the light foams in budget sofa beds.
- The base matters as much as the mattress: our models pair the pocket sprung mattress with zigzag springs and a flexible plywood frame working underneath it.
- Every Sofa Bed Expert model, from the £1,125 chair bed to the U-shaped, sleeps on pocket springs. There is no foam-only model in the range.
The three sofa bed mattress types
1. Foam mattresses
A foam sofa bed mattress is a slab of polyurethane foam that folds inside the sofa. It is light, cheap to make and fine for a guest once or twice a year. The weakness is fatigue: foam compresses where your hips lie, and low-density foam does not spring back. In cheap sofa beds this shows as a visible dip within a year or two of regular use. Foam quality varies enormously, which is why the density number matters more than the word "foam" itself.
2. Open sprung mattresses
Open sprung (also called bonnell or, in a different form, zigzag sprung) mattresses use a connected web of springs. Because the springs are linked, pressing one moves its neighbours: support is decent but generalised, and two sleepers feel each other turn. In a good sofa bed, zigzag springs do their best work not as the mattress but under it, in the seat and base, where they add suspension. That is exactly how we use them.
3. Pocket sprung mattresses
A pocket sprung mattress wraps each spring in its own fabric pocket. Every spring compresses independently, so your shoulder can sink while your waist is supported, and a partner turning over on a king size bed does not roll you into the middle. It is the technology used in quality standalone beds, and it is why a good pocket sprung sofa bed can honestly be called an every-night bed. Every Sofa Bed Expert sofa bed uses a pocket sprung mattress and pocket sprung seats, so the sofa sits as well as the bed sleeps.
| Type | How it supports you | Best for | Watch out for |
|---|---|---|---|
| Foam only | One surface compressing as a block | Occasional guests | Low density flattens with regular use |
| Open sprung | Connected springs move together | Occasional to regular use | Sleepers feel each other move |
| Pocket sprung | Each spring works independently | Every-night sleeping | Check what is under the mattress too |
What does 50 kg/m³ foam actually mean?
Foam density measures how much material is packed into each cubic metre. More material means more structure to push back night after night. Budget sofa cushions often use light foams that feel fine in the shop and flatten at home; high-resilience foam at 50 kg/m³, the grade used across our range, is engineered to recover its shape and keep doing so for years. Density is not softness: a dense foam can be soft or firm. It is longevity. If a retailer will not tell you the density, that is an answer too.
The mattress is half the story: check the base
A pocket sprung mattress on a saggy base sleeps like a saggy base. What sits underneath decides how the mattress performs, which is why our construction stacks three layers: a strong, flexible plywood frame that flexes without cracking, zigzag springs that give the base suspension, and the pocket sprung mattress with high-density foam on top. The same recipe runs through the whole range, from the Millbrook Chair Bed at £1,125 to the Mocca U-Shaped, with weight capacities from 250 kg on the chair beds up to 500 kg on the U-shape.
"Wanted a new sofa bed comfortable as both sofa and bed. I have chronic pain from spinal damage and as a sofa, even I find it more comfortable than any others."
Mr Graham Smith, verified customer review
How to read a sofa bed product page
- "Pocket sprung mattress" in the specification, not just the headline. Some listings say sprung and mean the seat only. Ours state pocket springs in both mattress and seats.
- A foam density figure. Look for 35 kg/m³ or higher; we use 50 kg/m³ high-resilience foam.
- The frame material. Plywood or hardwood outlasts particleboard and MDF.
- The sleeping dimensions. A real bed length is 200 cm or more; our beds run 180 to 280 cm long. If the sleeping size is not listed, ask why.
- Weight capacity. A number (ours run 250 to 500 kg) shows the maker has tested it.
The ten-minute test: whichever brand you are considering, lie on the open bed for ten minutes on your usual sleeping side. Pocket springs reveal themselves: shoulders and hips settle in while your waist stays supported. You can do exactly this at our Bognor Regis showroom.
Caring for a sprung sofa bed mattress
Pocket sprung mattresses need little: air the bed every few weeks by leaving it open for an hour, use a fitted sheet cut for your model (100% cotton, from £22) so the mattress itself stays clean, and close the mechanism gently rather than dropping it. The springs do not need rotating or flipping; the mattress folds with the mechanism as designed.
Frequently asked questions
What is the most comfortable sofa bed mattress type?
Pocket sprung is the most comfortable type for regular sleeping, because each spring is wrapped in its own pocket and compresses independently, supporting hips and shoulders separately. Every Sofa Bed Expert sofa bed has a pocket sprung mattress and seats as standard.
Are foam sofa bed mattresses any good?
Foam mattresses suit occasional guest use. Their lifespan depends on density: low-density foam flattens with regular sleeping, while high-resilience foam holds its shape far longer. For every-night use, a pocket sprung mattress is the better choice.
What does 50 kg per cubic metre foam mean?
It is the foam's density: 50 kg of material per cubic metre. Higher density means more structure, better shape recovery and a longer life. Sofa Bed Expert uses 50 kg/m³ high-resilience foam alongside pocket and zigzag springs.
What is the difference between pocket sprung and open sprung?
Open sprung mattresses use connected springs that move together, so pressure in one spot moves the surrounding area. Pocket sprung mattresses wrap each spring individually, so each one responds only to the weight directly above it, giving more precise support and less partner disturbance.
Can you sleep on a pocket sprung sofa bed every night?
Yes. A pocket sprung mattress on a supportive base is designed for nightly use. Sofa Bed Expert sofa beds pair the pocket sprung mattress with zigzag springs and a flexible plywood frame, and are sold as every-night beds with weight capacities of 250 to 500 kg.
Do sofa bed mattresses need flipping or rotating?
No. A sofa bed mattress is attached to the mechanism and folds with it by design. To keep it fresh, air the open bed every few weeks and use a fitted sheet so the sleeping surface stays clean.
How thick should a sofa bed mattress be?
As a rule of thumb, mattresses under 8 cm suit occasional use only. More important than thickness alone is construction: a pocket sprung mattress on a sprung base outperforms a thicker slab of low-density foam.
Which Sofa Bed Expert models have a pocket sprung mattress?
All of them. Every model in the range, from the Millbrook and Oslo chair beds through the Millbrook and Mocca sofa beds to the Tampa and the Mocca U-Shaped, has a pocket sprung mattress and pocket sprung seats as standard.
The bottom line
Buy the mattress, not the silhouette. Foam for the once-a-year guest, pocket springs for everyone else, a density number you can see, and a sprung base underneath doing the quiet work. That combination is standard across our range, which is why we call every model an every-night bed and mean it.
Pocket springs as standard, in every single model
Pocket sprung mattress and seats, 50 kg/m³ high-resilience foam and a flexible plywood frame, from the £1,125 chair bed to the U-shaped.
Explore all sofa beds → Read: mechanisms explained →Related reading: Best highly sprung sofa beds · Sofa bed sizes UK · Try before you buy
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