Twelve mistakes people make buying a mattress

Mistake 01

Shopping by spring count

It is the number on every label and the first thing salespeople reach for. It is also, as far as we can establish, the least regulated figure in the industry. We searched for a British Standard, a National Bed Federation rule and Trading Standards guidance on how spring counts are advertised, and found none; if such a standard exists we would genuinely like to be told about it.

A specialist UK retailer describes three practices it says are common in the trade: quoting counts at king size regardless of the size being bought, so a "1,000 spring" single contains roughly half that; stacking sheets of tiny micro-springs above the support layer; and counting divan base springs into the mattress figure.¹ That source sells traditional high-filling mattresses and positions itself against high spring counts, so it is not disinterested — but the underlying arithmetic is checkable, and we have found nothing contradicting it.

The part that matters: a mattress is a fixed height, so every spring layer added is upholstery removed. A 4,000-spring mattress and a 1,000-spring mattress of the same depth may have identical support cores, with the extra 3,000 springs occupying space that would otherwise hold wool, cotton or foam.

Mistake 02

Reading the guarantee length and stopping there

Ten years sounds like ten years of protection. It rarely is.

TEMPUR's UK guarantee publishes a cost-sharing scale. Claim in year six and you pay 10% of the current list price toward a replacement. Year eight is 30%. By year fifteen it is 95%.² Note it is calculated on today's price, not what you paid.

Simba takes a different route to a similar place. Its ten-year guarantee requires a dip of 25mm in the first six months — but 70mm between years five and ten.³ That is roughly the depth of a clenched fist. A mattress can be visibly sagging and uncomfortable at 40mm and still be working as designed.

Mistake 03

Keeping the old bed base

The commonest way to void a guarantee, and it happens before the first night's sleep. Every brand specifies a maximum slat gap, and they do not agree with each other.

A base with 9cm gaps is compliant for DreamCloud and outside the stated limits for Sealy and Simba.⁴ It is rarely raised at the point of sale, which is perhaps unsurprising when the base is not the thing being sold.

Mistake 04

Confusing the trial with the guarantee

They are separate things, running on separate clocks, with separate conditions.

The trial covers changing your mind about comfort. The guarantee covers manufacturing defects. A mattress you simply do not like is a trial matter and never a guarantee claim, because comfort preference is explicitly excluded from every guarantee we have read.

The conditions vary more than the headline nights suggest. Silentnight's 365-night trial covers only the just sleep range, requires a minimum of 28 nights first, and is an exchange rather than a refund.⁵ Panda's widely quoted 30-night trial is for toppers and pillows; the mattress trial is 100 nights.⁶

Mistake 05

Buying by size name

Bed sizes are national and the names collide. A UK king is 150 × 200cm. A European king is 160 × 200cm. A US king is 193 × 203cm — 43cm wider than ours. A US queen, at 152 × 203cm, is wider and longer than a UK king despite sounding smaller.

This matters more than it used to, because a great deal of the mattress content people read online is American, and because imported bedding is easy to buy by accident.

Mistake 06

Believing the firmness will fix your back

Worth being careful here, because the marketing is confident and the evidence is not.

The "medium-firm is best for back pain" claim traces overwhelmingly to a single trial: Kovacs and colleagues, published in The Lancet in 2003, 313 Spanish adults with chronic lower back pain over 90 days.⁷ Medium-firm did better than firm on pain in bed. Worth knowing that pain on rising was not statistically significant.

A 2021 systematic review covering 39 studies found that just seven were randomised controlled trials.⁸ And across the literature there is essentially no good evidence that any particular construction — memory foam, pocket sprung, hybrid, latex — outperforms another for back pain.

“Orthopaedic” is not a protected term in UK trading standards so far as we can establish, and we have found no certification scheme behind it. Brands may use it to describe a firmer build, which is a reasonable everyday meaning — it simply is not a clinical one.

Mistake 07

Paying extra for cooling

Two different things are sold under the word. Thermal gel raises surface conductivity so the mattress feels cool to first touch — a sensation, not heat removal. Phase-change gel absorbs heat as it softens, which works until it has absorbed all it can.

That limit is inherent, not a fault. The peer-reviewed literature on phase-change materials in textiles describes the effect as "temporary or transient... effective as a barrier to thermal energy until all latent heat... is absorbed".⁹ A sleeper produces heat all night; a fixed store of cooling runs out early. The familiar "cool for an hour, hot by three" experience is the predicted behaviour.

It is also the most complained-about claim in the trade. The UK sleep industry figure James Wilson notes that one of the most common complaints he hears is from people who bought products marketed as "cooling" or "temperature regulating" only to find they still wake up hot, and has argued for clearer standards.¹⁰

Mistake 08

Trusting the discount

Discounting in this sector is close to continuous, which makes a headline percentage hard to interpret. Some publishers now advise readers to disregard RRP entirely.

The Advertising Standards Authority upheld a complaint against Nectar Sleep in August 2026 over a "save up to 65%" claim that was benchmarked against three competitors' prices rather than Nectar's own usual selling price. The ASA held the saving was not based on an established, genuinely available reference price.¹²

Mistake 09

Not thinking about weight until it arrives

Simba is one of the few UK brands to publish weights, and the spread within one brand is startling: a king ranges from 23kg to 57kg depending entirely on specification.¹³

This connects to the guarantee. Most brands require regular rotation, and failing to rotate is a documented reason to reject a claim — OTTY states plainly that it "might invalidate your warranty".¹⁴ The HSE's guideline lifting figures are 25kg for men and 16kg for women under ideal conditions.¹⁵ Almost every double and above exceeds that.

Mistake 10

Skipping the protector

Every guarantee we have read excludes mattresses that are stained, soiled or unhygienic. TEMPUR's wording covers a mattress that is "very stained, soiled and/or otherwise unhygienic"; DreamCloud lists "burns, cuts, tears, liquid damage, or stains".²¹⁶

One spilled drink can therefore end a ten-year guarantee on day one. A protector costs a fraction of the mattress and is the single cheapest thing you can do to keep the cover intact.

Mistake 11

Not registering it, and binning the label

Hypnos requires you to register the guarantee to activate it, and requires claims in writing within one month of noticing the fault.¹⁸ An unregistered Hypnos has no cover at all, which most owners discover at the worst moment.

On the label: the American "do not remove under penalty of law" tag has no UK equivalent, so cutting it off breaks no law. But it carries the batch and product identification the manufacturer needs to work out what you own. Without it a claim becomes much harder.

Mistake 12

Going to the manufacturer when something goes wrong

The most expensive mistake on this list, and it happens after the sale.

Under the Consumer Rights Act 2015 your statutory rights are against the retailer who sold it to you — not the brand that made it. The official Trading Standards guidance is explicit that a trader "cannot deny a consumer their statutory rights and direct them instead to their rights under the guarantee or warranty", and that an expired guarantee does not mean expired statutory rights.¹⁹

Between 31 days and six months the burden of proof sits with the trader, not you. After six months it flips back, and you can act for up to six years in England and Wales, five in Scotland — though a refund at that stage may be reduced to account for the use you have had.²⁰