Sat navs and car accessories How to buy a roof box

Buying a roof box

All the roof boxes we tested will fit most cars with roof bars, but check at the shop that a box is OK for your car. This generally means making sure your roof rack (or roof bars as they are sometimes known) are not too thick for the roof box's mountings.

Some cars come with roof bars fitted; for others, you can buy them from a dealer or auto shop (prices vary widely, depending on the car).

If you don’t already have a roof rack, expect to pay around £60 for a good third party model. Most of the products we looked at require bars of less than 80mm in width and between 18 and 35mm in height. 

You also need to consider the distance between the bars; larger roof boxes often need the bars to be further apart to ensure a stable, safe fitting.

Before you buy, dig out your car's handbook to find out more about fitting a roof box and if there is anything in particular to your vehicle. While you're looking, check the car's maximum roof load so you don't exceed it – roof boxes typically take loads of up to 50kg.

Check the size claims

An open roof box containing bags

Make sure that the box stores as much as its makers claim

The storage space the roof boxes claim to have falls way short of the actual usable space. In fact, the difference between the two can be up to 133 litres. Check the measurements before you buy.

And it's not just how much you can stuff inside that counts. Remember to measure how much space you have if you want to use it under a car port (cars usually won't fit into a garage once the roof box is attached).

Skiers, choose roof boxes carefully

We tested the roof boxes in extreme temperatures, and found that skiers and snowboarders need to choose carefully – if you accidentally dropped one of the weaker roof boxes in cold weather, the plastic could be brittle enough to crack.

Think about your valuables in roof boxes

It's all too easy to steal from roof boxes – only three of the roof boxes we tested resist casual lock-picking.

With more professional thieves' tools, only two put up a fight. They're all fairly flimsy, though, so even better locks wouldn't secure any of the roof boxes against a determined thief.

Safety is vital

We checked how loose objects such as skateboards or tent-poles damage roof boxes in a low-speed crash.

If one of these came crashing through the roof box and hit someone, it could be nasty. Most were fine, but one of the roof boxes only just scraped a pass on this test.

So, they may just be boxes, but there's plenty to think about before buying. As an alternative, you can hire a roof box similar to those we tested for about £50 a week. Either way, stay box clever and keep an eye out for our Best Buy roof boxes.

Where to buy a roof box

Though something as large as a roof box or cycle carrier may not strike you as lending itself to being bought online, it’s actually a reasonable way to buy. The delivery charge isn’t as bad as you’d think – £10 or so from Roofboxes, or around £15 if you go to Halfords website.

Roof box manufacturers' websites are worth checking out, too. Thule’s one lets you check that the roof box you want is compatible with your car. You can even see how it’ll look atop your vehicle thanks to the website’s MatchMaker tool. 

If you want to buy one straight away, branches of Halfords are your best bet, though they generally only stock Thule and own-brand models.

Other sections in this guide

  1. Overview
  2. Best Buy roof boxes
  3. Other roof boxes on test
  4. Roof box features
  5. How we test roof boxes
  6. How to buy a roof box