Underfloor Storage and Car Seats
- Mar 25
- 2 min read
Underfloor storage compartments are common in many cars, especially in the rear footwell.
They’re handy for stashing bits and bobs… but when it comes to car seats, they can introduce a safety issue that’s easy to miss.
What is underfloor storage?
Underfloor storage is a compartment built into the vehicle floor, often covered by a removable lid.
You’ll usually find it:
In the rear passenger footwells
Sometimes in the boot area
At first glance, it looks like a solid surface - but underneath, it’s hollow.
Why does it matter for car seats?
This becomes important when using a car seat with a support leg.
Support legs are designed to:
Transfer crash forces into the vehicle floor
Stabilise the seat
Reduce forward rotation
For them to work properly, they need to rest on a solid, load-bearing surface.
What’s the risk?
If a support leg is placed on top of an underfloor storage compartment:
The lid may not be designed to withstand crash forces
It could collapse or give way in a collision
This may affect how the car seat performs
Even if it feels solid during installation, it hasn’t necessarily been tested under crash conditions.
Can I still use a seat with a support leg?
Yes - but only if it’s approved for use with your specific vehicle setup.
Your options may include:
Extending the leg into the bottom of the box
Using a different seating position without storage
Checking if your vehicle manufacturer allows it
Using an approved filler designed for that compartment
Installing the seat in a position that the leg misses the box (but is still installed as per the seat manual)
Choosing a seat that doesn’t rely on a support leg
What is a filler?
Some vehicle or car seat manufacturers provide approved inserts (fillers) for underfloor storage compartments.
These are designed to:
Reinforce the space
Provide a load-bearing surface for the support leg
Important:
Not all compartments have approved fillers
DIY solutions (like foam, or polystyrene blocks) are not safe
Only use a filler if it is:
Approved by the vehicle manufacturer
Specifically designed for that compartment
How do I check if I have underfloor storage?
Look in your rear footwell for a visible lid or handle
Check your vehicle manual
If unsure, gently lift the floor section to confirm
FAQs
Can I ignore underfloor storage if the leg feels stable?
No - stability during installation doesn’t reflect what happens in a crash.
Do all support legs have the same rules?
No - guidance can vary by manufacturer, so always check both your car seat manual and vehicle manual.
