Waterproofing a convertible top: A step-by-step guide

A well-maintained fabric soft top is the result of taking the right steps at the right time. Waterproofing is one of those tasks that many drivers both overestimate and underestimate. In this article, you’ll find out exactly which steps are necessary when waterproofing and how to protect your soft top effectively.

When waterproofing is really necessary

Not every softtop automatically needs regular waterproofing. Many fabric tops, particularly Sonnenland tops, retain excellent water-repellency for several years, requiring no further treatment whatsoever. Whether a new protective coating is necessary is not determined by the calendar, but by how the water behaves. If raindrops no longer roll off cleanly but instead collect on the fabric as dark, matt patches, the original protective effect has worn off. A noticeably slower drying time after rain also indicates that the fabric is absorbing moisture more easily. In such cases, waterproofing is worthwhile to make the fibres more resilient again and to protect the fabric permanently against moisture penetration.

Why the right location is crucial

Effective waterproofing does not begin with the product, but with the environment. Heat, direct sunlight and wind can significantly disrupt the process and cause the protective coating to be absorbed unevenly or to dry too quickly. A shady, dry spot offers the best conditions – ideally with no strong wind and at a comfortable temperature. To ensure the new protective layer adheres properly, the soft top should first be free of surface dirt. You’ll find detailed instructions on how to clean it properly in our article on soft top care, which includes a step-by-step guide on how to prepare your soft top gently, thoroughly and in a way that’s suitable for the material.

How to use the waterproofing agent correctly

Once the softtop is completely dry after cleaning and the conditions are right, the waterproofing agent can be applied. Sensitive areas of the vehicle, such as painted surfaces, glass or seals, can be protected with a cloth or plastic sheeting to prevent any residue from forming later. The agent is then spread evenly, taking care not to soak the fabric excessively. In practice, a fine spray application has proven particularly effective, whilst a soft sponge is well suited for targeted treatment of seams or areas subject to greater wear and tear. It is sufficient for the fabric to be visibly damp and for the waterproofing agent to be absorbed evenly into the fibres without forming droplets or pools of moisture.

It is important to work calmly and evenly. The fabric should not drip, nor should it be dampened only in patches. How much the material absorbs the product depends on the age of the soft top, how well it has been looked after to date, and its general condition. The decisive factors here are not only the method of application, but also the quality of the waterproofing agent. Many all-purpose waterproofing products designed for domestic use leave residues or offer only short-term protection, whilst high-quality specialist products deeply saturate the fibres and remain effective for much longer. For this task, we therefore recommend only products that have been specifically developed for fabric soft tops and can deliver lasting results under real-world conditions. You will find a carefully curated selection of such products in our KHM Shop. (Pflegeprodukte).

The drying phase – the underestimated step

Once applied, the fabric needs time above all else. During the drying phase, the vehicle should not be moved and the soft top should not be opened or closed. Depending on the temperature and humidity, this process may take several hours. It is worth allowing sufficient time for this, as the effectiveness of the protective layer depends largely on how well the waterproofing has bonded with the fibres. Only once the soft top is completely dry can you assess whether the treatment has been applied evenly or whether individual areas require a second thin coat.

How often it is advisable to waterproof something

There is no set interval. Some convertible owners can use their soft top for several years without any further treatment, whilst others, particularly if the car is stored outdoors permanently, need to treat it more frequently. The condition of the fabric and how it reacts to water are the most reliable indicators. Vehicles that are rarely exposed to sun and rain require significantly less maintenance, whilst those used intensively or models parked outdoors tend to benefit from the occasional protective treatment.

When a professional is the better choice

Waterproofing is no substitute for repairs and cannot rectify structural damage. If the soft top already looks very worn, the fabric has become rough, or moisture seeps in immediately despite correct application, there are strong arguments in favour of replacing the soft top. It is worth consulting experts to find a long-term solution.

Conclusion: The perfectly balanced protective care for your convertible

A convertible top only needs to be waterproofed if the fabric has visibly lost its protective properties. If you keep an eye on the condition of your top and allow the waterproofing agent to soak in patiently, you can reliably restore the material’s natural protection. Waterproofing is not an ongoing requirement, but rather an occasional maintenance task that helps restore the top’s resilience. You’ll find more detailed information on cleaning and day-to-day care in our article on soft-top care, which complements these instructions perfectly. If you’re still unsure whether treatment is necessary or if your soft-top is already showing more significant signs of wear, we at KHM are always happy to advise you personally – simply send us a short email at