How to fit a roof box: a complete guide to roof boxes
Learn how to fit, pack and drive with a roof box on your car.
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By Tia Harrison-North
Last updated: 10 February 2025
Learning how to fit a roof box to your car is a great idea if you want to maximise storage. Maybe your needs have changed, and you could do with a bit more space than your car allows, but you don’t want to switch to a whole new model.
A roof box is an external storage system that attaches to the top of your car using a roof rack and they're favourites of families and those with outdoorsy hobbies like camping.
Whether you already have a roof box or you're planning to get one, keep reading to find out how to fit one and how to pack it efficiently.
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How to fit a roof box to your car
To fit a roof box to your car, you’re first going to need a roof rack. Plenty of vehicles already have roof racks as standard, including many SUVs and estates.
You’ll need to be aware of the fitting system used for your roof box, as this needs to be compatible with your roof rack.
The two most common roof rack mounting systems are:
U-bolts – some roof rack systems have ‘U’ shaped bolts that clip around the roof bar and then secure the roof box using a plate or mounting bracket
Power click or grip mount – these use claw grips to attach to the roof rack bars. It’s one of the quickest systems
Once you know what roof rack system you have, you can set about fitting your box to the roof of your car.
You’ll need to:
Read the instructions of your roof box to get familiar with the process of fitting it
Lift the roof box on top of your vehicle, getting some help if needed
Align your box with the fitting system, whether you’re using U-bolts, power click/grip mounts, or another mounting system
Secure the box using the fitting system you’ve chosen (more details should be in the instructions, such as how tight the fixings should be)
Double-check to make sure the box is secure and locked in – check all the fixings again individually just to make sure
What size roof box fits my car?
Not every car can have a roof box. It depends on the size of the roof rack you can have, how much weight your car roof can bear and the shape of your roofline.
You’ll also need to check your car’s manual to find the loading weight for the roof of your car – and make sure you safely stick to that. Don't forget the max weight includes what's inside the roof box, so you might have to transport your anvil another way.
If you're stuck, some online tools let you search for roof boxes using your car's number plate or make and model.
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Top roof box packing tips
Once you’ve picked your roof box and got it fitted, you can start filling it up. There are a few things to remember though, especially when it comes to weight limits.
Know the weight limit
Each roof box and roof rack comes with a different weight limit, and each car comes with its own roof weight capacity as well. Sticking to the weight limits is important because they make sure your roof box is safe.
The maximum carry for roof boxes varies, but they're usually from 50kg to 75kg – so, plenty of space.
As long as the weight of what you're storing plus the weight of the roof box itself doesn't exceed your roof rack or car's weight capacity, you're in the clear.
Pack the heaviest bits in the car
Even with all that extra loading space at the top, it’s still a better idea to keep heavy items with you in the car. Your car will always have a larger weight limit, and it’s better for your centre of gravity to keep heavy loads low.
Save the roof box for awkward items
Your roof box is best saved for randomly shaped items like tents, camping furniture or sports equipment that can't be stacked neatly in your car.
Save your roof box space for this type of luggage to make sure you’re getting the most out of all your packing space.
Spread out the weight
To keep your ride smooth and balanced, load the heaviest items across the bottom of your roof box and distribute that weight evenly.
This will ensure that your ride stays smooth and quiet. We suggest placing the heaviest items in the centre of your roof box and packing around them, leaving little room for items to slide around.
Securing and locking
It’s an obvious one, but we’ve got to say it – make sure everything is secure before you head off!
Double-check your box is closed and locked securely, and see if you can get a spare key just in case.
You should also make sure that your box is securely fitted and there’s no risk of it coming loose from your roof rack.
How much is a roof box?
The cost of car roof boxes varies with the model you’re looking at, but they typically start at around £150 for a 320-litre model.
You might also be able to find some used options on selling sites, but just make sure they’re safe and secure before getting on the road with one.
How do roof tents work?
Like roof boxes, roof tents attach to the top of your car via roof rack or bars and can be opened up to create a sleeping space.
They’re ideal for a quick camping solution and can be attached to even small cars. Some roof tents can sleep up to four people and can be really comfortable (for a tent of course).
They can be quite expensive, depending on your budget, but there are great value models starting at around £300.
Explore used cars
Knowing how to fit a roof box is a handy skill if you’re an over-packer who needs extra space or someone who likes to head off camping.
Roof boxes can be fitted to most cars with roof racks, though adding heavy loads can decrease fuel efficiency.
Take a look at our full range of used cars to find something that will easily carry your roof box or tent.
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