Polyurethane Foam in Mattresses: HR Foam, Comfort Layers Explained
Polyurethane foam is the most common material in British budget and mid-range mattresses, forming the core support layers, comfort layers and sometimes the entire mattress. It is an open-cell foam produced by mixing polyols and diisocyanates; the resulting structure traps air that provides cushioning, support and breathability. High resilience (HR) foam is a denser, more elastic type of polyurethane foam that offers better bounce and durability than standard grades, while comfort layers are usually softer polyurethane or memory foam placed on top to relieve pressure points.
What Is Polyurethane Foam and Why Is It Used in Mattresses?
Polyurethane (PU) foam is a synthetic material manufactured to precise densities, typically measured in kilograms per cubic metre (kg/m³). In UK mattresses it must comply with BS 7177 fire safety regulations, which require specific flame-retardant treatments. Budget mattresses often rely entirely on layered PU foam because it is affordable, lightweight and can be cut to any UK size from small single 75x190cm (2ft6) up to super king 180x200cm (6ft). Mid-range models combine it with pocket springs or latex for hybrid performance. The foam’s open-cell structure allows air movement, helping to regulate temperature better than solid materials.
Standard Polyurethane Foam vs HR Foam
Standard PU foam usually has a density of 18–25 kg/m³ and is used in entry-level open-coil or basic foam mattresses. It compresses easily, which can lead to quicker sagging on heavier body weights. HR foam, by contrast, starts at around 35 kg/m³ and can reach 50+ kg/m³ in premium budget lines. The higher density gives greater resilience, meaning the foam springs back faster when you move. This makes HR foam suitable for medium-firm mattresses. Check the product page for the exact density quoted; higher numbers generally indicate longer lifespan.
Practical Checklist When Comparing Foam Densities
- Measure your mattress depth before buying – most foam-only mattresses are 15–25 cm total.
- For children or lighter adults under 60 kg, 25–30 kg/m³ foam is adequate in a kids mattress.
- Adults 80 kg and above benefit from HR foam of at least 35 kg/m³ in the support core.
- Press the corner of any display model firmly; good HR foam returns to shape within 2–3 seconds.
Comfort Layers: Memory Foam, Gel and Standard PU
Comfort layers sit directly under the cover and are usually 2–5 cm thick. Memory foam, a type of viscoelastic polyurethane, softens with body heat and moulds to pressure points, making it popular in memory foam mattresses. Gel-infused versions aim to improve heat dissipation. Standard PU comfort layers are cheaper and firmer, offering quicker recovery but less contouring. In hybrid designs the comfort layer works with pocket springs to prevent the sleeper feeling the coils. A practical rule: if you sleep on your side, choose a mattress with at least 3 cm of softer comfort foam; back sleepers usually need less than 4 cm to avoid sinking too far.
Polyurethane Foam in Kids’ and Cot Mattresses
UK cot mattresses are commonly 60x120cm and toddler/cot-bed versions 70x140cm. Safety rules are strict: foam must meet BS 7177 and the cover should be waterproof and wipeable. Many parents choose a Noomi Waterproof Eco Foam Mattress because the polyurethane core is dense enough for support yet light enough to lift easily. For older children moving to a cabin bed, a foam mattress of appropriate depth prevents the top-bunk guard rail from becoming ineffective; the rail must rise at least 16 cm above the mattress surface and top bunks are not recommended for children under 6. Always follow the BS EN 747 standard when purchasing bunk or cabin beds.
Choosing the Right Foam Mattress for UK Bed Sizes
Match the foam construction to the bed size and your weight. A single 90x190cm (3ft) mattress for one adult can use lighter foam than a king 150x200cm (5ft) shared by two people of differing weights. Medium-firm polyurethane mattresses suit most back and stomach sleepers; side sleepers often prefer a softer comfort layer. Consider a medium firm mattress if you are unsure. Hybrid options that combine HR foam comfort layers with pocket springs are widely available in double 135x190cm (4ft6) and above. EU sizes such as 140x200cm differ from UK standards, so double-check dimensions before ordering.
| Foam Type | Typical Density | Best For | Recovery Speed |
|---|---|---|---|
| Standard PU | 18–25 kg/m³ | Budget, guest rooms | Slow |
| HR Foam | 35–50 kg/m³ | Daily use, mid-range support | Fast |
| Memory Foam | 40–60 kg/m³ | Pressure relief, side sleeping | Very slow |
Maintenance and Longevity of Polyurethane Foam Mattresses
Rotate or flip non-tufted foam mattresses every 4–6 weeks to prevent uneven wear. Use a breathable mattress protector to guard against spills; polyurethane can absorb moisture if the cover is breached. Vacuum the surface monthly with a soft brush attachment. If the mattress develops a permanent body imprint deeper than 3 cm it is time to replace it. For eco-conscious shoppers, some ranges use recycled polyurethane; see the natural and eco-friendly mattresses category for options.
Shoppers looking for pure foam support can browse the full mattresses range, while those wanting bounce should also view pocket sprung mattresses that combine springs with polyurethane comfort layers.
Our picks for this guide
- Noomi Waterproof Eco Foam Mattress Single – Uses polyurethane foam with eco credentials and waterproof protection, ideal for children's or toddler use where easy cleaning and correct density are essential.
- SleepShaper Comfort 500 Memory Foam Mattress – Features memory foam comfort layers over a polyurethane base, giving pressure relief while staying within mid-range budgets.
- SleepShaper Supreme Comfort 700 Memory Foam Mattress – Higher specification polyurethane and memory foam construction provides thicker comfort layers suitable for king and super king sizes.
- Medium Firm Mattresses – Category includes many HR polyurethane foam models that deliver the balanced firmness most UK adults need without excessive sink.
Frequently asked questions
Is polyurethane foam safe for babies and toddlers?
Yes, when it meets UK fire safety standard BS 7177 and is used in a properly fitted cot or toddler mattress sized 60x120cm or 70x140cm. Waterproof covers prevent moisture damage. Always ensure the top bunk guard rail rises at least 16 cm above the mattress if using in a cabin bed.
What is the difference between HR foam and memory foam?
HR foam is a high-density polyurethane that provides fast bounce and support. Memory foam is viscoelastic polyurethane that contours slowly to body heat. HR foam suits those who want quicker response; memory foam is better for pressure relief on side sleeping.
How thick should a comfort layer be?
Most UK mattresses use 2–5 cm comfort layers. Side sleepers usually need at least 3–4 cm of softer foam or memory foam. Thicker layers increase sink but can reduce support if the core density is too low.
Can you recycle old polyurethane foam mattresses?
Many local councils accept foam mattresses at household waste centres. Some manufacturers operate take-back schemes. Look for ranges that use recycled content polyurethane if sustainability is important to you.
Are gel mattresses just polyurethane foam with gel added?
Yes. The gel is infused into the polyurethane comfort layer to help conduct heat away from the body. The base support is still standard or HR polyurethane foam. They are popular in the gel mattress category for warmer sleepers.
Related guides
- UK Fire Retardant Foam Laws for Mattresses and Beds
- Memory Foam Explained: Types, Densities and Off-Gassing UK
- Natural Latex Foam in Mattresses: Benefits and UK Fire Standards
- Mattresses for Shoulder Comfort and Pressure Relief
- Mattresses for Hip Comfort and Pressure Relief
- Foam vs Sprung Mattress for Bunk Beds: Which is Better?