A cot can look beautifully made and still require a careful safety check before your baby sleeps in it. Cot rail spacing is one of the details that deserves close attention: gaps that are too wide can create a risk of a baby’s head, limbs or clothing becoming trapped, while poorly maintained rails can compromise an otherwise safe sleep space.
For new and expecting parents, the reassuring news is that this is not something you need to guess. A well-designed cot from a reputable specialist should be made to the relevant safety requirements, clearly assembled and paired with a properly fitted mattress. Knowing what to look for helps you shop with confidence and maintain the cot safely as your child grows.
Why cot rail spacing matters
Cot rails are there to keep your baby safely within their sleep area while allowing fresh air to circulate. The spacing between the vertical bars is carefully considered. If the gaps are excessively wide, a baby may be able to put their head, arm or leg through them. If the gaps are unusually narrow, fingers and small limbs may be more likely to become caught.
For cots designed to recognised European and British safety requirements, including BS EN 716, the distance between adjacent bars is generally designed to fall between 25 mm and 60 mm. The maximum 60 mm measurement is especially useful for parents to remember. It is intended to prevent a baby’s head from passing through the opening.
That figure is a useful guide, not a reason to rely on a tape measure alone. The safest choice is a cot that is clearly labelled as complying with the appropriate standard and supplied with complete instructions. Product testing assesses more than the gap between rails - it also considers strength, stability, durable construction, moving parts and entrapment hazards.
Do not judge safety by appearance alone
Wide rail designs can suit a clean, Scandinavian-inspired nursery, but a spacious-looking design is not automatically unsafe. What matters is the actual measured opening and whether the cot has been manufactured and tested to the relevant standard.
Likewise, narrow slats do not guarantee a safer cot. Uneven spaces, loose bars, damaged joints or decorative cut-outs can all introduce risks. A premium cot should feel solid, have consistently positioned rails and use child-safe finishes that stand up to real family life.
How to check cot rail spacing at home
If you are setting up a new cot, begin with the manufacturer’s instructions. Assemble every component exactly as shown, using the supplied fittings only. A missing screw, swapped part or loosely fitted rail can affect the structure and the spacing between components.
Once assembled, inspect the full cot in good light. Look across each side rather than checking only the most visible area. The bars should be straight, firmly fixed and evenly placed, with no cracked wood, bent metal or sharp edges. Run your hand gently along the rails to check for rough patches, splinters or loose paint.
A simple ruler can help you understand the gap size, but do not force objects between rails or try to recreate a test at home. If a gap looks inconsistent, is wider than 60 mm, or changes when pressure is applied, stop using the cot until you have spoken to the retailer or manufacturer. Never try to correct rail spacing by adding padding, tying fabric around the bars or fitting homemade inserts.
For a second-hand cot, inspect even more carefully. Safety standards and product designs change over time, while repeated assembly, storage and household moves can weaken fittings. If you cannot confirm the cot’s manufacturer, age, instructions or safety compliance, choosing a new, certified cot is usually the more reassuring decision.
Mattress fit is just as important as rail spacing
A safe cot is a complete sleep system. Even perfectly spaced rails cannot compensate for a mattress that is too small, too soft or incorrectly positioned. The mattress should sit flat on the base, with no lifting corners or gaps around the edges where a baby could become trapped.
As a practical check, there should not be enough room for more than two fingers between the mattress and the cot sides. Use the mattress size recommended by the cot manufacturer rather than assuming a similarly sized mattress will fit. Cot dimensions can vary, and a mattress described as ‘standard’ may not be suitable for every model.
Choose a firm, flat mattress made for infant sleep. It should retain its shape and fit securely even after the fitted sheet is on. Avoid placing extra mattresses, folded blankets, cushions or foam toppers underneath or on top in an attempt to improve the fit. These additions can make the sleep surface uneven and create hazards.
Keep the cot clear
Rail spacing sometimes leads parents towards cot bumpers, especially if they worry about little arms and legs reaching through the bars. However, padded bumpers, loose bedding, pillows, soft toys and positioners can introduce other sleep risks. They can reduce airflow and may become tangled or cover a baby’s face.
For babies, the clearest arrangement is also the safest: a firm fitted mattress, a well-fitted sheet and appropriate sleep clothing or a correctly sized sleeping bag. If your baby puts an arm or leg briefly through the rails, they can usually reposition themselves. The answer is not to pad the cot, but to ensure the cot meets safety standards and remains in good condition.
Adjust the cot as your baby develops
Many cots have an adjustable mattress base. The higher setting is convenient for lifting a newborn in and out without straining your back, but it is only suitable while your baby is not yet sitting up or pulling themselves towards the sides.
Lower the mattress base as soon as your baby shows signs of sitting, rolling with purpose or attempting to pull up. Follow the specific timing and height guidance in your cot manual, as each model differs. This adjustment helps preserve the height of the side rails above your child and reduces the chance of climbing or falling.
Also remove anything that could become a foothold. Mobiles, cot toys, hanging organisers and nearby furniture may seem harmless, yet an increasingly mobile baby can use them to reach higher than expected. Position the cot away from windows, blind cords, lamps, shelves and heaters. A safe rail measurement is only one part of a safe nursery layout.
When a cot needs attention
Build a quick cot check into your regular nursery routine, particularly after moving the cot, changing the mattress height or cleaning around it. Tighten fittings only as instructed and replace damaged parts with approved replacements from the original manufacturer.
Stop using the cot and seek advice if you notice a loose or missing rail, a crack in the frame, damaged fixings, peeling finish, a warped mattress base or a side that no longer locks securely. The same applies if your child can climb over the rails, even if the cot is otherwise in good order. At that stage, it may be time to move to a suitable toddler bed.
Avoid improvised repairs. Tape, cable ties, household screws and added wooden pieces can create sharp points, unstable joints or new gaps. A cot is one piece of nursery furniture where certified compatibility matters far more than a quick fix.
Choosing a cot with confidence
When comparing cots, start with clear evidence of compliance with the relevant safety standard, then look at construction quality and day-to-day practicality. Solid rails, smooth non-toxic finishes, a secure adjustable base and an accurately matched mattress all contribute to a sleep space that feels considered from the first night onwards.
A showroom visit can be particularly helpful. Seeing a cot in person lets you assess the finish, test how smoothly the base adjusts and ask informed questions about mattress compatibility and care. At RaaB Family, we believe parents should be able to choose nursery furniture that looks at home in a modern space without making compromises on tested safety and dependable quality.
The most helpful habit is a simple one: whenever you change the sheet, take a moment to look at the rails, fittings and mattress fit. That small check keeps your baby’s cot ready for the quiet, restorative sleep they need.