Flat roof renovation with felt, metal, PVC/EPDM or PUR foam

The roof is one of the most important structural, functional, and aesthetic elements of a building. Its primary functions include:

• stabilization of the structure of the entire building,
• protection of the interior against precipitation and other destructive atmospheric phenomena,
• protection against heat loss or excessive heating,
• and finally the aesthetic function.

Maintaining the roof in proper technical condition to enable the above functions is crucial for the durability of the building and operating costs.

Flat roofs are very popular in multi-family, public and industrial buildings

It is also gaining more and more supporters among owners of single-family homes because it is about 20% cheaper to build, is not afraid of storms or hurricanes, has a smaller surface and offers greater arrangement possibilities (you can create usable space, e.g. a terrace or a green garden, which may not be possible on small, narrow plots) 

Preparing for flat roof repair 

When preparing to renovate a flat roof, we need to answer the following questions:

• What is the technical condition of the structure and roofing (it is a good idea to hire a professional company to perform such an inspection, but unfortunately you have to take into account the expense of PLN 500-2000 depending on the roof surface) 
• Do we want to enhance the roof's functionality in the future, e.g. with photovoltaics, a terrace function or a green garden?
• In addition to roof repairs, will it be necessary to repair utilities such as chimneys, ventilation outlets, etc.?
• When do we want to do it – what time of year?
• What durability do we want to achieve?
• What will the maintenance costs of a new roof be?

The answers to these questions will have a significant impact on the scope and technology of your roof renovation. We emphasize this stage because it's at the diagnosis and requirements stage that the most costly mistakes are made, and the temptation to take shortcuts or "just say it'll work out somehow" is also very common.

Diagnosis of technical condition

Roof renovation and minor damage/leaks, most often in the area of ​​chimney flashings and other flashings

If a flat roof inspection shows it to be in good technical condition, and potential risks are related to work around chimneys or ventilation outlets, for example, we recommend using Fillcoat – a sealant with or without fibers . This sealant is characterized by:

• Excellent adhesion to any surface 
• Possibility of application in all weather conditions 
• 1300% elasticity – so it will perfectly withstand all stresses related to different thermal expansion of materials – e.g. sheet metal/brick, brick/tar paper, roofing felt/sheet metal 
• Resistant to high and low temperatures, the lack of bitumen content means that it does not spread at high temperatures, as is the case with popular bituminous dispersions, and does not oxidize like bituminous masses 

By using Fillcoat or Fillcoat Fibres, you can quickly and independently repair, for example, a leaking roof in places where chimney flashings are installed, saving significant costs associated with the visit of a professional company that will do the same thing, but at a much higher price. 

FILLCOAT / FILLCOAT FIBERS

Instantly waterproof, flexible mass for roofs, impassable terraces, gutters, ridge tiles, chimneys, pipes, resistant to UV and acid rain.

Roof made of felt - Three repair technologies 

Is the covering degraded, with numerous cracks, blisters and other damage?

If the roof covering looks like the ones in the photos above, you should decide on a general renovation, and here we have basically three main technologies at our disposal:

1. The first one is to remove the old roofing felt, possibly repair the substrate and apply two layers of new roofing felt.
2. The second technology is to lay a new top covering felt on the old roofing felt.
3. The third is the use of liquid roofing membrane technology, which we will discuss in more detail below.

First, however, let us focus on the question marks regarding the first two roof waterproofing renovation technologies.

Renovation costs using roofing felt technology

The costs of roof renovation will play a significant role here, as the old roofing felt will have to be removed.

The average cost of removing roofing felt in 2023 ranged from PLN 30 to PLN 50 per square meter, and this applies to relatively simple roofs with a single layer of felt. The removed felt must then be disposed of in accordance with applicable regulations (felt is classified as hazardous waste with the code 17 03 80), resulting in a cost of around PLN 1,000 per ton (i.e., less than 200 square meters of felt). After removing the felt, the subfloor will undoubtedly require preparation, filling any unevenness and areas where water has pooled, and then applying two layers of felt.

Roof renovation with felt - cost

Depending on the region and the quality of the roofing felt used (underlayment and topcoat), you should expect an expense of around PLN 300/m2 for the full service (labor + materials). 

In the case of the second technology, the cost will certainly be lower due to the disposal of the roofing felt and the removal of the old roofing felt, but it will not be small either, because such a surface also needs to be prepared for the application of new heat-sealed roofing felt.

Note!!! When choosing the second technology, i.e. roofing felt on roofing felt, you need to check whether the ceiling / roof structure will withstand an additional load of approximately 6 kg/m2.

Limiting the options for further use of the roof and increasing the costs 

If we would like to use a flat roofing felt as a terrace surface in the future, we must take into account the additional costs of covering the felt with some terrace technology, a constant unpleasant smell during sunny days and quite complicated maintenance activities to prevent dirt from accumulating on the surface of the felt under the terrace system. 

Roof repair and photovoltaics

If we want to install photovoltaics, we must take into account that the efficiency of your installation will be 6 to 23% lower than expected, and this is due to the fact that the roofing felt can heat up to 80°C - we write about this in more detail here.

Comparison of flat roof waterproofing technologies 

Roof waterproofing using Neoproof Polyurea R as an example:

Liquid roof membrane technologies in roof waterproofing renovations

Liquid roofing membrane technologies such as Neoproof PU W-40 and Neoproof Polyurea R have been gaining more and more supporters for years thanks to the following advantages:

• High durability, even over 25 years 
• Low cost of maintenance in technical well-being (much lower than in traditional technologies) 
• Jointless technology – no risk of leaks at joints as in the case of roofing felt
• No significant load on the roof structure 
• Versatile application. Can be applied to any previously prepared substrate – roofing felt, shingles, sheet metal, concrete, EPDM, PVC, and more
• Can be used in roof terrace systems without unnecessary additional costs 
• Can be used in the construction of green roofs - root penetration certificate 
• High chemical and UV resistance 
• Lowering the roof temperature – increasing the durability of the structure and more efficient use of renewable energy sources 
• Ease of maintenance and upkeep

The above advantages make investing in liquid membranes for waterproofing or repairing flat roofs optimal due to the average investment cost and low maintenance costs, which is especially important in times when all services and costs are increasing day by day, and the availability of qualified contractors is limited.

Trokentech not only offers roof renovation systems, but also support in roof diagnosis and selecting the right contractor.

Flat roof waterproofing step by step

Roof repair

Roofs covered with felt can lose their tightness over time and begin to leak. This can be caused by weathering or improper installation. Leaks are usually difficult to pinpoint because water may enter from a completely different place than where it exits. Instead of applying successive layers of felt, which may not necessarily solve the problem, we can use waterproof membranes.

STEP 1 – preparing the substrate

Emulsol RN-1 cleaning concentrate , but remember to rinse it thoroughly afterward. Wait for the surface to dry before proceeding.

STEP 2 – applying a fungicide

The next step is to protect the substrate with Grzybostop . This product can be applied by spraying, roller, or brush. After spraying the roof, wait 24 hours.

STEP 3 – completing joints and finishing

Neotex PU Joint polyurethane sealant to joints and sheet metal flashings . This sealant is designed for extrusion using a gun.

Protection of machining areas with Neotex PU Joint .

STEP 4 – application of the waterproofing membrane

Next, you can apply Neoproof Polyurea R directly to the felt. For waterproof membranes, first apply Revinex diluted 1:4 and allow to dry (approx. 2 hours).

Applying the membrane should begin at the joints and seams. Apply Neotextile , and then immediately cover with a second layer of coating.

Applying the first layer of Neoproof Polyurea R after covering the processing and joints

The second coat should be applied after approximately 18 hours (25°C), preferably in a crisscross pattern with the first. The coating has waterproofing properties and can be exposed to rain within an hour of application.

Roof protected with Neoproof Polyurea R

Metal roof repair

Using the example of a roof covered with trapezoidal aluminum sheet, we will show how to create a tight membrane to prevent leaks.

As you can see, the roof was in poor condition. It had been patched with strips of roofing felt, which didn't adhere well and didn't provide a seal. The roof also leaked at mechanical fasteners, flashings, and vents.

STEP 1 - preparing the substrate 

Good preparation of the substrate is very important, as any dirt left on the surface may impair the adhesion and durability of the coating. 

For cleaning metal surfaces, we recommend Emulsol RN-1 . Dilute it with water to a concentration of 2-3%. It's best to pressure wash the roof. Then rinse the roof with water only and allow it to dry.

STEP 2 – application of rust remover

If rust is present on the roof surface, it must be removed immediately. In hard-to-reach or poorly cleaned areas, use Top-Kor rust remover (under Neoproof Polyurea R/C1) or Neodur Metal Force (when applying water-based coatings).

Top-Kor can be repainted 12 hours after application. Coverage is 10 m²/l.

Neodur Metal Force can be repainted after 24 hours. Consumption is 50 ml/m2.

We can also use the innovative product RAYSTON PU AL PRIMER 1K , which can be applied to corroded places without the need for preparation to class S2i1/2 and is an excellent substitute for the Top-Kor product.

STEP 3 – priming the substrate

Under water-based membranes on aluminum, use Vinyfix Primer diluted 15% with Neotex 1080 (for water-based coatings). The first layer of topcoat can be applied approximately 12 hours (25°C) after applying the primer.

, Rayston PU Al Primer 1K should be used as a primer .

Revinex primer to the felt surface . It stabilizes the grit on the felt and ensures good adhesion of the topcoat. The product is diluted with water at a ratio of 1 part Revinex to 4 parts water. Theoretical consumption after dilution is 0.04 kg/m².

Roofing felt primed with Revinex

STEP 4 – filling the gaps 

Gaps and cracks should be filled with Jointex . Apply the sealant with a spatula. Once dry, proceed to apply the waterproofing membrane.

STEP 5 – application of waterproofing membrane

The roof shown was waterproofed using the Neoroof .

If there are no visible cracks on the roof and there is no need to bridge the different materials, you can apply one layer of primer and two layers of Neoroof. In the case of this roof, three layers of Neoroof with Neotextile reinforcement mesh were used. 

When using a system with reinforcing mesh, apply one coat first, then glue the mesh in place while wet, and immediately paint over it with a second coat, preferably applied perpendicular to the first. It's crucial not to trap any air bubbles under the mesh – at higher temperatures, the air will expand and could damage the coating. Apply the third coat after it has dried (at least 24 hours). 

Finished, renovated and sealed roof

Renovation of a roof covered with a PVC/EPDM membrane

PVC/EPDM membranes are a popular roof covering, but if they start to leak over time, they can be easily sealed with Neoproof PU W-40 or Neoproof Polyurea R . To do this, you first need to properly prepare the substrate.

Roof before painting

STEP 1 – thoroughly cleaning the surface

Emulsol RN-1 cleaning concentrate , but remember to rinse it thoroughly afterward. Wait for the surface to dry before proceeding.

STEP 2 - washing the substrate with MEK thinner

We wash the substrate with MEK (methyl ethyl ketone) thinner. This process aims to gently dissolve the PVC membrane to ensure adhesion of the topcoat.

Theoretical consumption of thinner will be approximately 100 grams/m2.

STEP 3 – Applying Vinyfix Primer

Vinyfix Primer diluted 15% with Neotex 1080 to the sticky PVC membrane . Approximately 12 hours (25 degrees C) after applying the primer, the first layer of topcoat can be applied.

STEP 4 – application of the Neoproof PU W-40 waterproof membrane

Twelve hours after applying the primer, apply the first layer of the Neoproof PU W-40 . 24 hours after the first coat, apply the second layer. This is a water-soluble, liquid product that is applied like traditional paint. Theoretical consumption for two coats is approximately 1.3 kg/m². If the PVC membrane has cracks or areas requiring treatment (fireplaces, walls, air conditioners), we also use Neotextile . Apply three coats of Neoproof PU W-40 to these areas.

First of all, we process fireplaces, skylights, etc.

Painting the first layer

Laying the reinforcing mesh

Covering the Neotextile mesh with a second coat of paint

It is important that no air bubbles remain under the net

Finished, renovated and sealed roof

When applying the Neoproof Polyurea R , skip STEP 3 (do not prime the substrate). After slightly dissolving the PVC membrane, apply Neoproof Polyurea R directly.

Sealing a roof covered with PUR foam

PUR foam has many advantages – it creates a continuous, homogeneous structure, eliminating any joints or thermal bridges. It's ideal for covering surfaces with unusual shapes, as spraying can reach every nook and cranny, and it provides excellent thermal insulation. However, it's not UV-resistant, so it shouldn't be used as a final coating on flat roofs. It should be topcoated with a suitable liquid waterproofing membrane, which will block out sunlight and resist any potential waterlogging.

Roof covered with PUR foam

STEP 1 – preparing the substrate

Neoproof Polyurea C1 topcoat directly over new foam, but with old PUR foam, you must first properly prepare the substrate. To do this, thoroughly wash the roof and allow it to dry. If there are any old, flaking coatings on the roof, they should come off. The foam will likely have open pores in these areas. Therefore, a suitable primer should be used in these areas.

STEP 2 – priming the substrate

Open-cell, degraded foam should be primed with Acqua Primer NP . This water-based primer is diluted 10-15% with water. After repainting, wait 24 hours (25°C). The primer can be applied at a minimum temperature of 12°C.

If the foam is in good condition, you can skip step 2. 

If Neoproof PU W-40 , the substrate should be primed with Revinex . Dilute the primer with water in a 1:4 ratio and leave to dry for approximately 2 hours.

If applying over old but well-adhered coatings, use Revinex primer Neoproof PU W-40 Neoproof Polyurea C1 can be applied directly.

STEP 3 – application of waterproofing membrane

Apply Neoproof Polyurea C1 in a single coat. Theoretical consumption is approximately 0.75 kg/m². The coating is rain-resistant just two hours after application!

Neoproof PU W-40 should be applied in two layers. Apply the second layer 24 hours after the first application (25°C), crossing the first layer. The coating hardens after approximately 7 days.

Roof made of PUR foam protected with Neoproof PU W-40

PUR foam roof protected with Neoproof Polyurea C1

Liquid waterproofing - basic products

NEOROOF

Waterproof, acrylic coating for painting roofs

A hybrid roof sealant that cures under UV radiation. Suitable for use on roofs with standing water. Resistant to low temperatures down to -35°C, it provides complete sealing and protection against water. 

Properties

• Easy application,
• Creates a smooth, homogeneous, flexible membrane that covers hairline cracks and provides complete protection against moisture and resistance to standing water,
• After two days of exposure to sunlight, the coating becomes resistant to dirt, which means it stays fresh longer and does not stick even at high temperatures,
• Resistant to temperature fluctuations, which is necessary for roof coatings (from -30°C to +80°C),
• has the CE mark – a system for surface protection of concrete,
• Remains flexible in a wide temperature range from -40°C to +80°C,
• Environmentally and user-friendly (one-component, water-based product),
• Easy application (roller application),
• Wide range of applications.

NEOPROOF PU W-40

Waterproof polyurethane coating for roofs

An elastomeric roof coating used when the highest mechanical strength and exceptional waterproofing properties are required. It creates a moisture-impermeable membrane that is resistant to UV radiation and mechanical stress.

Properties

• High mechanical strength,
• Resistance to stagnant water,
• The resulting coating has no joints,
• Resistance to ultraviolet radiation and unfavorable weather conditions,
• Can be applied in cloudy weather (cures through evaporation, does not require UV radiation),
• Remains flexible in a wide temperature range from -40°C to +80°C,
• Minimum ambient temperature during application 5°C,
• Environmentally and user-friendly (one-component, water-based product),
• Wide range of applications,
• Easy application (roller application),
• Ensuring a long service life – up to 22 years!

NEOPROOF POLYUREA R and NEOPROOF POLYUREA C1

Innovative polyurea coating for roller application

Neoproof Polyurea is an innovative polyurea system for roof sealing. It creates highly durable, waterproof coatings. Unlike typical polyurea products, it does not require the use of special equipment for hot spraying – the products can be applied with a brush or roller.

Properties

• High mechanical strength
• Resistance to stagnant water,
• Uniform coating without any joints
• Resistance to ultraviolet radiation – does not require additional layers to protect against sunlight,
• Resistance to early rainfall – depending on the version, rain may fall just 1-3 hours after application!
• Flexibility over 400%,
• Wide range of applications, can be applied to various substrates
• Zero water absorption,
• Wide range of applications,
• Easy application (roller application),
• Ensuring a long service life – up to 30 years!

Comparison of liquid waterproofing coatings offered by Trokentech

Is it worth repairing a felt roof?

Absolutely! As one of the most important structural elements of a building, the roof should be maintained in good condition. Any roof leaks dramatically increase the building's maintenance costs associated with repairs to the rooms located beneath the roof. Furthermore, properly repairing a roof made of felt, for example, by using liquid waterproofing membranes, can improve its protective function, protecting the building's interior from precipitation and excessive heat, and also positively impact the efficiency of the photovoltaic installation.

When to repair a felt roof?

Roof felt repairs using liquid waterproofing membranes are best carried out between April and October, or during favorable weather conditions. When repairing a roof using water-based products like Neoproof PU W -40 , it's crucial to pay attention to the dew point, so even favorable weather conditions allow for short application times. Neoproof Polyurea R become rain-resistant within one hour of application, making them suitable for applications in February or March. If leaks are noticed on a roof covered with roof felt during the fall and winter months, we recommend using Filcoat or Fillcoat Fibres for quick repairs.

Do you want to repair your roof with cold felt, but don't know how to choose the right products?

Choosing the right products for cold-rolled felt roof repair is crucial to the durability and effectiveness of the repair. It's also worth consulting a professional who can help you select the right products for your specific conditions and repair needs. At TrokenTech, we offer technical advice and will carefully select the right set of roof repair products.