Can I put a cushion on the booster seat?

A recent Ask the Expert question:

“My child complains that the booster seat is too hard and that it hurts their bum. I have noticed that the seat is very hard, there’s no padding at all. Can I add a cushion to the seat to make it more comfy?”

We have also had this enquiry in the past:

"My 3 year old keeps escaping from the 5 point harness, so he has moved to a high back booster seat with adult seat belt.  The seat belt sits up on his neck though, even when it's through the red guide.  Can I put a cushion under him to lift him up more so it doesn't rub on his neck?"

Example of what we've seen at our free car seat checking events

(NOTE: above pictures would be considered incorrectly fitted)

This blog is going to look at the potential risks involved in adding a cushion to the booster seat, and what else you can do to make the seat more comfortable.

In infant seats, group 1 seats and group 123 car seats, you normally find that the seat has some sort of insert in it that can be removed as the child grows. This doesn’t happen with high back boosters however, the seat comes as is, and it grows with your child by increasing the height of the head support.

When a child moves up to a high back booster (group 2,3) car seat, the booster is used as a belt positioning device. It lifts the child up so the adult seat belt will fit across their hips correctly. Booster seats nowadays go a step further than this, with many offering additional torso support and side impact protection.

What would the risks be if I put a cushion on the booster seat?

The potential risk is that the cushion would compress in an impact and cause the child to slip underneath the seat belt. This may cause them to be ejected from the seat belt, or receive greater injuries due to the belt not being positioned correctly.

I need to put a cushion on though, as my 3 year old doesn’t fit, and he can’t go in a harness seat because he escapes!

If a child has moved up to a high back booster seat they must weigh a minimum of 15kg, and be tall enough to fit within the seat belt – this is defined as the lap belt being flat over the lap, across the hips, and the shoulder belt running from the child’s hip to their shoulder. The shoulder belt should sit diagonally across their body and run level across their collar bone/shoulder. It shouldn’t slip off the shoulder (head rest too low) or sit up on their neck (head rest too high).

If a child doesn’t physically fit into the booster seat, then they are too small for it and are not able to safely use the seat. The child must return to their harness seat, or a seat with impact shield may work better. See our blog on the car seat harness for tips on how to stop your little one escaping.

How can the seat be made more comfortable?

If you do long journeys with your child, you may want to consider replacing their seat with something more padded – there are differences between the boosters and what comfort they can offer. Some boosters are very hard, which won’t be at all pleasant on a long journey!

We would not suggest padding a seat out with memory foam or DIY inserts – these have not been crash tested and there is just no way of knowing how they will effect the performance of a seat until you have a crash.

What about an adult seat cushion?

There are many cushions available for the adult vehicle seat, but these are mainly to assist with posture and back issues. They have not been developed or tested to be used with a child restraint and may affect the performance of the seat.