Silentnight Waterproof Deep Mattress Protector: How Deep a Mattress Does It Fit?

If you have a deep mattress — memory foam, hybrid, or anything over 25cm — finding a waterproof protector that actually stays put is harder than it sounds. The Silentnight Waterproof Deep Mattress Protector is one of the most widely stocked options in the UK, and the key question parents ask is simple: how deep a mattress does it actually fit? The answer is up to 38cm, which covers the vast majority of mattresses in UK homes. Here is everything you need to know before buying.

What Depth Mattress Does the Silentnight Waterproof Deep Mattress Protector Fit?

The Silentnight Waterproof Deep Mattress Protector is designed to fit mattresses up to 38cm (approximately 15 inches) deep. This is achieved through a generously elasticated skirt — a fitted sheet-style design rather than a flat pad — that wraps under the mattress and holds in place through the night.

For context:

• Budget single mattresses (common in children’s bedrooms): typically 15–20cm deep
• Mid-range mattresses: typically 20–28cm deep
• Premium, hybrid, or memory foam mattresses: typically 28–35cm deep
• Ultra-deep or luxury mattresses: can exceed 35cm, occasionally reaching 40cm+

In practice, a 38cm limit comfortably covers the vast majority of UK household mattresses, including most memory foam and hybrid models. If your mattress is over 38cm deep — unusual, but possible with high-end or handmade models — this protector may not sit securely and you would need to check the exact depth before purchasing.

Children’s mattresses, including standard single and bunk bed sizes, are almost always well within this limit. Bunk bed mattresses in particular tend to be shallower (10–18cm) for safety reasons, meaning the deep-fit skirt will have plenty of excess room to tuck under.

Construction and Materials

Top Surface

The top layer is terry cotton, which gives it a soft, towelling feel rather than the cold, smooth plastic surface that many cheaper waterproof protectors use. For children who are sensitive to textures — or who simply sleep better without the sensation of lying on what feels like a shower curtain — this matters.

Terry towelling also tends to be less noisy. The crinkle or rustle that can wake light sleepers is less pronounced here than with polyurethane-film-only products, though some noise remains when a child shifts position significantly. On balance, this is among the quieter options in its price bracket.

Waterproof Layer

Beneath the terry surface sits a waterproof barrier layer designed to prevent liquid reaching the mattress. This is the core function for anyone managing bedwetting: even if a pull-up or night product leaks, the mattress itself should remain dry and odour-free.

It is worth being clear about what a mattress protector does and does not do. It protects the mattress. It does not keep the child dry, does not contain urine within a product, and is not a substitute for absorbent nightwear or pull-ups for heavier wetters. It is the last line of defence, not the first.

Washing

The Silentnight Deep Mattress Protector is machine washable at 60°C, which is the recommended temperature for hygiene when managing bedwetting. Many cheaper alternatives only wash at 40°C, which is less effective at eliminating bacteria and odour over time. The 60°C washability is a genuine practical advantage for families doing frequent laundry.

Sizes Available

The protector is available in the following UK standard sizes:

• Single
• Double
• King
• Super King

There is no small single or cot size listed in the standard range, so for very young children or toddler beds, you would need a different product. For children in a standard UK single bed — which covers most school-age children — the single size is appropriate.

Where to Buy and Approximate Cost

The Silentnight Waterproof Deep Mattress Protector is widely available from Amazon, John Lewis, Argos, and directly from Silentnight. Prices vary by retailer and fluctuate with promotions, but as a rough guide:

• Single: approximately £18–£25
• Double: approximately £22–£30
• King: approximately £28–£38

It is worth checking multiple retailers, as the same product can vary by several pounds. Buying two for a child’s bed — so one is always available while the other is in the wash — is a common approach among parents managing regular wet nights, and at this price point it remains reasonable.

Is This the Right Mattress Protector for Bedwetting?

A fitted waterproof mattress protector like this one is a sensible foundation for any bedwetting setup. It does not replace the primary containment product — whether that is a pull-up, a taped brief, or a bed pad — but it means that if that product fails overnight, the mattress is not ruined.

Mattresses are expensive to replace and difficult to clean thoroughly once saturated. Even a single heavy leak can leave odour that persists despite surface cleaning. A protector at this price point pays for itself quickly.

That said, if your child wets heavily or rolls around a lot in their sleep, a fitted protector alone may not be sufficient. Many families use a layered approach: fitted waterproof mattress protector underneath, then an absorbent bed pad on top of that, with the absorbent nightwear on the child. If you find leaks are bypassing the pull-up entirely and reaching the bed, it is worth reading about why overnight pull-ups leak — there are structural reasons this happens that product-switching alone rarely solves.

Sensory Considerations

For children with sensory sensitivities — including many autistic children — the feel and sound of a mattress protector can be a significant issue. The terry surface of the Silentnight Deep Protector is softer and less clinical than many alternatives. It is not entirely silent, but it is meaningfully quieter than hard PU-backed products. If texture and noise are genuine barriers for your child, this is worth noting when comparing options.

What It Does Not Do

To be direct: a mattress protector will not reduce how often your child wets, improve product containment, or address any of the underlying reasons for bedwetting. If you are exploring those questions — whether that is understanding the science, working out what products to use, or deciding whether to speak to a GP — those are separate conversations. This product simply protects the mattress, which is a legitimate and necessary goal in its own right.

If the emotional and practical weight of regular wet nights is something you are managing alongside the practical side, how other parents manage the exhaustion of night changes is worth a read — particularly if you are handling most of this alone.

Verdict: Does the Depth Work?

The Silentnight Waterproof Deep Mattress Protector fits mattresses up to 38cm deep — enough to cover virtually every standard UK mattress, including thick memory foam and hybrid models. For children’s single beds, bunk beds, and guest beds, it will fit without issue. The terry surface, 60°C washability, and secure elasticated fit make it a practical and widely trusted choice for families managing bedwetting.

If you are unsure whether your mattress is within the depth range, measure from the base to the top surface before ordering. Most UK single mattresses fall well below 30cm, so unless you have invested in a particularly deep model, the fit should not be a concern.

For a broader look at how mattress protection fits into overnight management — and where it sits relative to bed pads, pull-ups, and other products — the most common complaints parents have about overnight leaks gives a useful overview of where things typically go wrong and why.