How to Repair a Roof with Roofing Paper? A Comprehensive Guide

Roofs covered with felt, while offering many advantages, can experience problems over time, including loss of waterproofing. Weather conditions, temperature changes, and the natural wear and tear of the material can lead to damage that can impact the roof's functionality. Fortunately, many innovative solutions are available today that allow for quick and effective repair of these troublesome problems. Thanks to modern technologies, it's possible not only to restore full waterproofing but also to extend the roof's lifespan. In this article, we'll discuss in detail all the key steps necessary to repair a felt roof to restore its original functionality and water protection. 

What is a roofing felt and what are its properties?

Bituminous felt is one of the most common roofing materials, particularly in industrial and residential buildings. Roofing felt is a bituminous material that initially exhibits good sealing and weather resistance. Over time, certain problems arise, leading to roof leaks. We describe these problems and how to address them in the following article.

What are the advantages of a roof made of felt?

• Waterproof – effectively protects the building against moisture.
• Easy repair – sealing a roof with roofing felt does not require complicated tools.
• Good thermal insulation – especially when combined with the appropriate underlay.
• Availability and low price – materials for repairing a felt roof are readily available.

What are the most common problems with felt roofs?

• Cracks and delamination – caused by UV rays and temperature fluctuations. Trapped moisture, combined with high temperatures, leads to bubbles forming on the roof surface.
• Leaks – occurring as a result of material wear or improper installation. These can subsequently lead to mold growth and the degradation of the entire roof surface.
• Mechanical damage – e.g. by strong wind, hail or heavy objects.

Repair of local damage to the roof

Air bubbles often appear on the felt. In such cases, they should be cut, thoroughly dried, and filled with a suitable elastic material. Cracks or small holes are treated similarly.

Depending on the technology you plan to use, you can use various products: Jointex® – recommended for water-based systems; Neotex® PU Joint – designed for two-component solvent-based systems.

Spot repair helps prevent further damage and prepares the roof for proper waterproofing.

Strengthening sensitive areas

Wherever there's a higher risk of leaks—such as at the joints between the roof and verticals or at edges—additional reinforcement is used. In practice, this means embedding a special nonwoven fabric, such as Neotextile® , in the first layer of the membrane. This creates an additional, flexible barrier that increases the membrane's resistance to structural movements and stresses.

Priming - the key to adhesion

Priming is a step that significantly impacts the final renovation result. A well-chosen primer ensures optimal adhesion and uniform substrate absorption.

The most commonly used primers include Revinex® – for water-based systems; Neopox® Primer BM – an epoxy primer for uncoated substrates, used for solvent-based systems.

This primer creates a solid base for membrane application, ensuring the durability of the entire system.

Application of a waterproofing membrane to the roof

Once the substrate is prepared, you can begin applying the waterproofing membrane. Two layers are typically recommended – ideally in different colors to easily control surface coverage.

A sample workflow: cleaning and degreasing the surface, repairing cracks and bubbles, priming with a suitable primer, reinforcing critical areas with non-woven fabric, applying the first layer of membrane, and applying a second layer in a contrasting color.

A two-layer system ensures a watertight and highly resistant coating.

Which waterproofing coatings should I choose?

There are many systems available on the market, but polyurethane and polyurea solutions are particularly recommended. A prime example is Neoproof® Polyurea R , a membrane characterized by excellent UV and weather resistance, flexibility even at low temperatures, and the ability to be applied without the need for priming. Furthermore, it holds European Technical Approval (ETA 24/1247) in the highest class W3, ensuring durability of up to 25 years.

Benefits of renovating roofing felt with waterproofing membranes

• Seamless - the lack of joints eliminates the weakest points of traditional roofing.
• Flexibility - the membrane works together with the structure, does not crack during thermal movements.
• Easy maintenance - the smooth surface prevents dirt and moss from accumulating.
• Resistance to weather conditions - rain, snow, frost or UV radiation are not a problem.
• Quick application - liquid systems allow you to minimize renovation time.
• Savings - a well-executed renovation extends the life of the roof by several years, which significantly reduces costs compared to replacing the entire roof covering.

Summary

Repairing a felt roof is a process that requires careful attention and adherence to the proper procedures. First, assess the condition of the roof covering, then thoroughly clean it, repair any damage, prime it, reinforce critical areas, and finally cover it with a waterproofing membrane. Only this approach ensures lasting results and waterproofing the building.

Modern resin and polyurethane systems achieve significantly better results than traditional felt – both in terms of durability and aesthetics. By investing in the right materials and professional workmanship, you can achieve a roof that is watertight and safe for over 20 years!