Roof box purchasing advice: how to choose the right product

  • What You Need to Know
  • The roof box or roof box extends the storage space of the car for luggage, sports equipment or shopping.
  • The box has several advantages over a trailer: parking spaces are easier to find, there is no need for tiresome manoeuvring and no extra driving licence is required.
  • Roof boxes differ not only in length, width and volume, but also in material. There are also soft boxes made of fabric containing plastic.
  • Drivers have to adjust to a changed driving experience: The car is heavier, has a larger side surface and higher fuel consumption.
  • Whether roof rails, rain gutters or T-slot rails – roof boxes are attached in different ways depending on the car roof.

More storage space thanks to roof box

In a roof box for the car, drivers can carry extra cargo for which there is no more room in the boot or on the back seat. Roof boxes are relatively light and made of robust plastic material. Some can be loaded with up to 80 kilograms of additional weight. They are therefore particularly suitable for people who have to transport a lot of cargo that would actually be too big for the car. For families with children or a dog, it can quickly become cramped inside the vehicle if everyone has their own suitcase or travel bag. A roof box – or roof box – can help. But even those who need comprehensive equipment for holidays or excursions, such as skiing, diving or surfing, are well advised to use a roof box.

The roof boxes are sometimes rectangular with rounded edges, but some are also very long and narrow. The designers have made sure that the objects are streamlined. This way, they harmonise visually with the vehicle and affect the driving behaviour and fuel consumption as little as possible. In most cases, the boxes slope slightly flatter towards the front. Because of this appearance and aerodynamics, they are often also called jet bags.

What makes a roof box?

Car roof boxes have a low weight and are easy to install. They can be attached to the vehicle with the help of a roof rack. Even long or bulky items that cannot be stowed in the boot can find a place here. The boxes are made of robust material that can withstand knocks and bumps. They are also resistant to external influences such as rain, sunlight and dust pollution. No special driver’s licence is required for transport.

The roof box is a practical companion not only for trips and excursions when large amounts of luggage have to be transported. It can also be used for larger purchases, for example at the furniture store. The permissible roof load of the car must always be taken into account. This varies from vehicle to vehicle and can be checked by the driver in the manual. If the limit is exceeded, safety is no longer fully guaranteed. Apart from this, however, there are no particular restrictions as far as the type of vehicle is concerned; correspondingly compact roof boxes are also available for smaller models. Due to their streamlined shape, they are not a safety risk even when driving on the motorway, yet most manufacturers recommend not exceeding a speed of 130 kilometres per hour. It is important that the driver adopts a safe driving style and deals conscientiously with the changed driving conditions. The jet bags usually have little air resistance and stay on the roof without jerking because they are firmly secured.

The models can usually be locked separately and offer the option of securing the load inside with tension belts or nets. There is often a non-slip mat on the floor of the box to prevent the additional luggage from being thrown around. Even extreme weather cannot harm the roof box, as it is not only waterproof but also very weather-resistant.

Another advantage of stowing your extra load on the roof instead of inside the car is the unrestricted view. If you stack your boot to the brim, you can no longer see through the rear windows. So before thinking about a trailer or even a new car, drivers should consider a roof box. This is a much more comfortable and cheaper alternative when it comes to increasing storage space.

Woman loading roof box
Roof boxes are suitable for stowing luggage for which there is no more room in the interior of the car.

Which roof box is right for me?

Roof boxes come in different sizes and shapes. The smaller versions usually have a volume of around 250 to 275 litres, while larger models can sometimes hold twice as much. Therefore, the user should carefully consider how much space he or she really needs, what it will be used for regularly and whether anything else will fit in the boot. The roof boxes differ from one another especially in length – from one metre to a good 1.90 metres, everything is possible. Extra-wide or flat models are also available. For safety reasons, it is important that the box is not longer or wider than the roof. If it protrudes too far to the rear, it can also block the boot.

Therefore, consider what you regularly transport or what you want to use the roof box for in the future – it should be as large as necessary, but also as small as possible. There are flat and almost roof-wide models, compact and somewhat taller versions, as well as very long and narrow variants. If you want to pack your ski equipment, a 1.20 metre long luggage box is not enough. A box of the maximum size, but always only half loaded, has dimensions that are too impractical for the purpose. It unnecessarily increases weight and side area, which leads to higher fuel consumption. A problem that can be avoided with proper planning.

Car with roof box

What are the advantages of a roof box over a trailer?

If you regularly want to transport larger quantities by car, you might think about buying a trailer. Up to a certain point, however, a roof box might be sufficient. Compared to a small trailer, it already has decisive advantages. The car does not take up any extra space, so finding a parking space is no more difficult. There is also no need for complicated manoeuvring, which can be a nuisance with a trailer. The speed limit is significantly higher, but fuel consumption is lower. A trailer even requires an extra driving licence. Last but not least, a roof box is considerably cheaper to buy.

How does the driving behaviour change with a roof box?

In any case, be aware that a bulging roof box affects driving behaviour. Even experienced drivers should familiarise themselves with this feeling before going on a long trip. The vehicle is heavier overall, and fuel consumption is automatically higher as a result. The side area of the vehicle is larger with the attachment. This can be particularly noticeable after forest sections and on bridges, as any gusts of wind from the side have a larger catching surface here. The centre of gravity is also slightly higher, which changes the situation in curves in particular. So be prepared to drive differently with a roof box and adjust your driving behaviour accordingly. Keep a greater distance from other vehicles, especially on the motorway.

Hard and soft roof boxes

Roof boxes are made of different materials. The boxes are always characterised by a very light dead weight. Regardless of the type of shoring, they are available in different sizes. Whatever material you choose, the roof box is stable and protected against all weather conditions and dirt. It is also resistant to impacts and violence, so thieves don’t stand a chance. In addition to the rigid models, there are also elastic and foldable boxes that have some advantages and disadvantages.

The plastic ABS (acrylonitrile butadiene styrene) is one of the most common materials for the production of roof boxes. It is robust and cheap to manufacture, which is reflected in the final price for the consumer. However, it cannot be ruled out that parts made of ABS will bend, especially under high loads. As a higher-quality and therefore somewhat more expensive alternative, there are models made of glass-fibre reinforced plastic (GRP). This material is much more dimensionally stable and durable than ABS. This results in lower wind resistance. For frequent use, especially for long distances, it is advisable to use roof boxes of this type.

Foldable roof boxes made of plastic fabric – also called soft boxes – are even lighter than the hard cases. Once folded, they can be stored in a space-saving way and carried in the vehicle. The outer shell is flexible and soft, but protects the contents from water and dirt, just like conventional roof boxes. The maximum payload weight varies depending on the size, but is comparable to that of rigid boxes.

The foldable box is usually stabilised with a wire frame or half-shells made of plastic and is approved for speeds of up to about 130 kilometres per hour. Even though the material protects the contents and the roof box can be secured with a padlock, thieves could slit it open with a knife. Therefore, you should only use the box for transport and not leave it unattended on the roof when valuable luggage is inside. The price for the softbox is significantly lower than for its hard colleagues, which can be an argument for buying it if you use it sporadically.

How to mount the box on the roof

It can be mounted on the roof of almost any model of car, with restrictions for some sports cars or very small cars. Jetbags cannot be mounted on convertible roofs either. The design of the body varies depending on the requirements of the roofs; in any case, however, a roof rack must be available. Just make sure that it is compatible with the roof box, but this should not be a problem with common roof rack designs.

 Mounting the roof box

Mounting options

Depending on the vehicle, owners of a roof box have various fastening options. In general, four common variants can be distinguished.

  • Roof rails
  • Rain gutter
  • T-slot rail
  • Mounting points

Some vehicles are equipped with a so-called roof rail from the factory. Sturdy cross struts, which form the roof rack, can be attached to this. If there is no roof rail, the struts can be attached to the edge of the car roof – the rain gutter – using claw-shaped brackets. Other vehicles offer extra mounting points at the corners of the roof for luggage racks or their holders, which are protected with plastic covers. Narrow rails (“T-nuts”) are also often installed on the long sides of the roof for this application. Before setting up, find out exactly what requirements the roof of your vehicle has for the carriers and which mounts are compatible with them.

Special case: Suction cups / magnetic surfaces without roof rack

There are a few models of roof boxes that can be attached directly to the roof of the vehicle without any other brackets or carriers. Here they adhere with suction cups or magnetic surfaces. However, experts only advise the use of these boxes to a limited extent. Heavily packed and in the fast airstream, strong forces act on them, which can become a major factor of insecurity. If you cannot avoid using this type of roof box, you should handle it with particular care.

Mounting the roof boxes

Always mount the roof box empty and get help if the mounting becomes a bit more confusing – especially with larger vehicles. Consult the manufacturer’s manual if you are unsure or if you are installing the roof box for the first time. Basically, the underside of the roof box is connected to the luggage rack. The exact design or handling of this fastening differs from manufacturer to manufacturer. To prevent the box from slipping during assembly, you can fix it with rubber stoppers. Assembly should be relatively easy, especially if two people are involved. Beforehand, it is best to clean the places where the crossbars are connected to the roof box and the railing. Check for signs of wear and the condition of the connections and brackets to ensure a non-slip grip. Experts also recommend that, if possible, the box should be placed so that heavy loads can be accommodated at the height of the vehicle pillars, as this is where the vehicle is most stable.

Tips for optimal use

For better comfort, the driver should make sure that the roof box can be opened from both sides – as is the case with the models presented. This way, he does not have to keep this in mind when looking for a parking space. Some suppliers equip the box with a central locking system, which provides additional security. This means that the key can only be removed when all the individual components are closed.

Softer items of luggage such as blankets or sleeping bags are best stowed in the front part of the roof box. This way, heavier items are better cushioned in the event of hard braking. These in turn should be placed as centrally as possible and at the bottom of the roof box for the best possible centre of gravity. Long, inflexible items such as skis or snowboards should be packed first. If particularly heavy parts increase the roof load too much, it is better to store them in the boot. If in doubt, this also applies to items that are sensitive to moisture.

Always make sure that you do not exceed both the permissible roof load and the total weight of the vehicle after loading. For optimum safety, the driver should check again a few kilometres after setting off to make sure that the roof box and load are optimally secured. Take your time and check that all parts interlock and that the box is really tight. An inadequately secured roof box can become a life-threatening projectile in the event of an accident or even just a hard braking manoeuvre.

Keys for roof box

What extras are useful for the roof box?

To protect the roof box from dirt and scratches when not in use, a suitable protective cover can be pulled over the model. For foldable boxes, storage bags can be purchased for this purpose. For storage in the garage or cellar, you can attach special holders for the boxes to the walls, which saves storage space. Even more space-saving are the roof box lifts, which pull the object up and hold it under the ceiling. Inside, there should be provisions for additionally securing the load. These can be straps or carrying nets that are attached to the inside wall of the roof box with hooks. Some models have individual compartments or dividers to separate different types of cargo. Some manufacturers also offer roof box bags to store clothes neatly, for example.