Bunk Bed Mattress Thickness Guide: What Depth is Best?
For UK bunk beds the best mattress thickness is usually 12-15 cm. This depth keeps the top bunk guard rail at least 16 cm above the mattress surface as required by BS EN 747, reducing fall risk while still providing adequate comfort for children.
Why Mattress Depth Matters for Bunk Beds
UK bunk beds must meet BS EN 747 safety standards. The top-bunk guard rail has to rise a minimum of 16 cm above the mattress. If you choose a thicker mattress the effective height of the rail drops, which can make the bed unsafe. A mattress that is too thin may lack support and comfort.
Most standard UK bunk beds are designed around single-size mattresses measuring 90x190 cm (3ft). Depths over 18 cm often push the rail height below the legal minimum on many frames, so always check the specific bunk bed instructions for maximum mattress depth.
Standard UK Bunk Bed Mattress Sizes and Depths
UK bunk beds almost always use single mattresses. Here are the common dimensions:
- Small single: 75x190 cm (2ft6) – mainly for younger children or space-saving designs
- Single: 90x190 cm (3ft) – the most common bunk bed size
Cot mattresses (60x120 cm) and cot bed sizes (70x140 cm) are only suitable for very young children or specific low bunk/toddler configurations. EU sizes such as 90x200 cm single or 140x200 cm double will not fit standard UK bunk frames.
For thickness, 10-15 cm is the practical range for most bunk beds. Thicker options reduce headroom and compromise the guard rail height on the top bunk.
| Mattress Depth | Typical Use | Guard Rail Clearance | Suitability for Top Bunk |
|---|---|---|---|
| 10-12 cm | Younger children, space-saving | Usually 18 cm+ | Very safe |
| 12-15 cm | Most families, balanced comfort | 16-18 cm | Safe on compliant frames |
| 15-18 cm | Older children needing more cushioning | May drop below 16 cm | Check frame specs carefully |
Safety Checklist Before Buying a Bunk Bed Mattress
Use this practical checklist to ensure compliance and safety:
- Confirm the bunk bed states its maximum mattress depth – never exceed it.
- Measure current guard rail height from the slat base and subtract your chosen mattress depth; the result must be at least 16 cm.
- Choose only mattresses that meet UK fire safety regulations (BS 7177).
- For the top bunk, avoid memory foam or hybrid mattresses thicker than 15 cm unless the frame is specifically designed for them.
- Check that the mattress fits the frame without overhanging the edges.
- Top bunks are not recommended for children under 6 years old regardless of mattress thickness.
Shop our full range of bunk beds to see frames with clear maximum depth guidance.
Best Mattress Types for Bunk Beds
Open coil and pocket sprung mattresses in the 12-15 cm range offer good value and breathability. Memory foam and hybrid options provide pressure relief but are often thicker, so they suit the bottom bunk better.
For children, waterproof and easy-clean surfaces are practical. The Noomi Waterproof Eco Foam Mattress Single is an excellent low-profile choice at a safe depth for both bunks.
If you prefer traditional support, consider pocket sprung models from trusted names. Browse our kids mattresses or the wider single mattresses selection.
Flair, Solace+Co, Maxitex, Recoil and Noomi Options
These brands offer mattresses well suited to bunk bed use. Maxitex and Noomi produce practical depths that work within most guard rail limits. Recoil and Flair also supply complementary bunk frames that state compatible mattress depths clearly.
Look at memory foam mattresses for the lower bunk where extra depth is less critical. For all-round use, medium firm mattresses in single size give reliable support without excessive thickness.
Decision Rules for Choosing Thickness
Follow these rules for safe choices:
- If the bunk bed is for a child aged 6 or under, keep the top bunk mattress at or below 12 cm and consider using only the bottom bunk.
- For children over 6, 13-15 cm usually works on standard frames.
- Measure the distance from the top of the slats to the top of the guard rail; subtract at least 16 cm to find your maximum mattress depth.
- Bottom bunks can safely take up to 20 cm mattresses since there is no fall risk.
- Always buy UK-sized mattresses (90x190 cm for single) rather than EU equivalents.
Pair your choice with a suitable frame such as the Flair Eloise Bus Bunk Bed White or the Noomi Kayla Bunk Bed with Storage White, both designed with practical mattress depths in mind.
Common Mistakes to Avoid
Many parents choose the thickest mattress believing it equals better comfort. This often violates the 16 cm guard rail rule and reduces headroom. Others buy adult-sized thick memory foam mattresses that simply do not fit the frame width or length. Always verify exact specifications on the product page before ordering.
Consider standard bunk beds that clearly list compatible mattress depths to simplify the decision.
Our picks for this guide
- Noomi Waterproof Eco Foam Mattress Single – Slim profile stays safely within most bunk bed guard rail limits while offering waterproof protection ideal for children.
- Flair Eloise Bus Bunk Bed White – Designed with clear mattress depth guidance that keeps the top bunk guard rail compliant when paired with 12-15 cm mattresses.
- Noomi Kayla Bunk Bed with Storage White – FSC-certified frame states compatible mattress depths that work well with thinner single mattresses for safe top-bunk use.
- Kids' Mattresses – Range includes multiple 12-15 cm options specifically developed for bunk beds and compliant with UK safety standards.
Frequently asked questions
Can I use a 20 cm thick mattress on a top bunk?
Usually no. A 20 cm mattress will leave most standard UK bunk bed guard rails below the required 16 cm minimum height above the mattress surface. Reserve thicker mattresses for the bottom bunk only and always check the specific frame’s maximum depth rating.
What is the thinnest safe mattress for a bunk bed?
Around 10 cm is the practical minimum for comfort and support on most bunk beds. Thinner than this can feel too firm for children. Look for kids-specific options that balance thinness with adequate cushioning.
Do all bunk beds have the same maximum mattress depth?
No. Each model states its own limit based on the height of the guard rails. Low bunk or playhouse styles often allow only up to 12 cm while staircase designs may accept 15 cm. Always read the manufacturer’s guidance for the exact frame you are considering.
Are memory foam mattresses suitable for bunk beds?
They can be used but are often thicker than 15 cm, making them better suited to the bottom bunk. If using on the top bunk, select a slim memory foam version no more than 13 cm deep to maintain the required guard rail height.
Should I buy the same thickness for both bunks?
Not necessarily. The top bunk benefits from a thinner mattress to preserve guard rail safety. The bottom bunk can use a thicker, more luxurious option. This approach maximises safety and comfort for both sleeping positions.
Related guides
- How Much Depth Clearance Do You Need for a Bunk Bed Mattress?
- Bunk Bed Mattress Safety Standards Every UK Parent Should Know
- Maximum Mattress Depth for Bunk Beds with Guard Rails
- How to Protect a Bunk Bed Mattress from Dust and Mites
- Bunk Bed Mattress Weight Limits: What You Need to Know
- Best Mattress Toppers for Kids Bunk Beds to Add Comfort