Invest in Sleep

Section

Beds and bases

The base gets no attention at the point of sale and is the commonest way to void a guarantee.

The base gets almost no attention at the point of sale, because it is not usually what is being sold. It is also the commonest way to void a mattress guarantee, and it happens before the first night’s sleep.

Slat gaps: everyone publishes a different number

Every brand specifies a maximum gap between slats, and they do not agree with each other. A base that satisfies one manufacturer breaches another.

Chart showing the maximum slat gap permitted by each brand: Sealy 7.5cm, Simba under 3 inches, DreamCloud and Nectar 9cm. A base with 9cm gaps satisfies DreamCloud and Nectar but voids Sealy and Simba.
Maximum slat gap in each brand’s own UK guarantee or care terms, checked 29 August 2026.

Sealy pairs its 7.5cm maximum gap with a 10cm maximum slat width. Simba requires gaps under three inches and slats over two inches wide. DreamCloud and Nectar, which share terms, allow 9cm.

Silentnight’s figure is widely quoted online as 6cm, but that number appears only on third-party scraper sites and on no Silentnight page we could reach. We have left it out rather than repeat it on someone else’s authority. If you own a Silentnight mattress, ask them directly and get the answer in writing.

Before your mattress arrives

Measure the gaps on your existing base with a tape measure, and check your brand’s specific figure rather than a generic one. If the base is close to the limit, a sheet of hardboard or a bunkie board costs a great deal less than losing the guarantee.

Single-sided mattresses and what you may not do

Most modern mattresses are single-sided: all the comfort filling is on one face. Turning one over puts you on the unupholstered side, and Sealy lists exactly that as a voiding condition. These mattresses are rotated head-to-foot, never flipped.

Nor may you re-roll a vacuum-packed mattress. The National Bed Federation is explicit that bending or rolling a mattress permanently damages the spring unit and invalidates the guarantee — which matters if you are moving house and thinking of putting it back in its box.

Weight, stairs and access

A king-size mattress can weigh anywhere from 23kg to 57kg depending on specification. The HSE’s guideline lifting figures are 25kg for men and 16kg for women in ideal conditions, so almost every double and above is a two-person job. Measure the route in — staircase turns, landing width, whether the flat has a lift — before ordering a traditional sprung mattress, which cannot be compressed to get it through.