Frequently asked questions

The primary purpose of foundation waterproofing is to protect the building from the effects of water and moisture. Properly applied waterproofing ensures the foundation's longevity and prevents corrosion of both the concrete and the reinforcement. The absence of waterproofing, or a poorly installed one, allows moisture or water to penetrate into the building, leading to the growth of fungi and mould, deterioration of plaster and paint, or even flooding of the basement.

The term “soil and water conditions” refers to a combination of factors that describe the ground's properties and the local groundwater level. These conditions are crucial for designing, selecting products for, and carrying out construction projects. The appropriate waterproofing solution is chosen based on the type of soil, water conditions, potential presence of aggressive substances in the groundwater, and the landscape, which affects how water drains. Before you choose and begin foundation waterproofing work, you need to answer three key questions: 1. Does groundwater regularly or occasionally appear at or above the building's foundation? 2. Are there impermeable soils, such as clays, that could cause water to temporarily stagnate? 3. Does the building have a basement? Only after answering these questions can you determine the type of waterproofing needed (either damp-proofing or full waterproofing) and select the right solutions for the project.

For NEXLER Disperbit to be used for foundation waterproofing, all of the following conditions must be met: - Rainwater must be able to freely drain into layers of well-permeable soil, such as sand or gravel, below the foundation. - The highest potential groundwater level must be at least 30 cm lower than the bottom edge of the foundation. - The building must not have a basement and must be situated less than 3 meters below ground level. If any of these conditions are not met, a waterproofing compound from the NEXLER BITFLEX series, which are KMB-type masses, should be used instead.

If the foundation walls are constructed from small elements like concrete blocks, you can use NEXLER Fundament or a weldable bituminous felt, such as NEXLER PREMIUM PYE PV200 S40, for the horizontal footing waterproofing. The number and type of layers needed will depend on the specific waterproofing method you are using. However, if the foundation walls will be monolithically connected to the footing, you should not use roll materials like weldable bituminous felt for the horizontal waterproofing on the footing. The reinforcing bars extending from the footing will interrupt the continuity of the felt. In this case, horizontal waterproofing must be created using a seamless material, such as a single-component micro particle sealing mortar like NEXLER AQUAMINERAL 1K Ultra. A coating made from this material is strong enough to withstand the loads transferred from the building's foundation walls.

No, NEXLER Fundament felt should be laid loosely on the concrete base. The overlapping felt seams must have a minimum width of 8 cm. It is particularly recommended for use on foundations for masonry load-bearing and partition walls. The felt is available in rolls that are 25 cm, 33 cm, and 50 cm wide.

NEXLER BITFLEX products are divided into single-component masses (NEXLER BITFLEX 1K, NEXLER BITFLEX 1KP) and two-component masses (NEXLER BITFLEX 2K, NEXLER BITFLEX 2KP). Single-component masses are ready to use. The reduced preparation time allows you to begin work faster, and since it can be stored properly after being opened, one package can be used over a longer period of time. Two-component products also include a powder component. The two components must be thoroughly mixed before application. The powder component causes the mixture to set not only through physical evaporation but also hydraulically, which significantly accelerates the process. This speeds up the formation of the coating by about four hours, and it becomes resistant to rain after approximately three hours. Unlike single-component products, two-component products must be used within a certain amount of time after they are mixed. Two-component masses are recommended for variable weather conditions, especially in early spring and late autumn, when there is a risk of precipitation or drops in temperature. Products with a "P" at the end of their name (NEXLER BITFLEX 1KP and NEXLER BITFLEX 2KP) contain a polystyrene filler, which improves efficiency by making application easier and faster. The polystyrene filler allows you to achieve the required layer thickness in a single application.

These are materials designed to protect buildings from the infiltration of radon and the alpha particles it emits. At high enough concentrations, these emissions due to radioactivity can negatively affect human health and increase the risk of cancer. NEXLER BITFLEX 1KP is a mass that provides an effective barrier against radon, as confirmed by tests from the Institute of Nuclear Physics. Additionally, bituminous felts from our product line, such as NEXLER Alu S40, NEXLER Alu Aquastoper SP, and NEXLER PREMIUM PYE G200 S40, offer effective protection against radon radiation.

This question must be answered on a case-by-case basis, depending on the materials used for the walls and the weather. In some situations, it may be possible to start after just two days. However, you must remember that the surface for the application must be continuous, bonded, properly cured, and able to bear a load. Waterproofing should only be applied to a substrate that has reached its full performance parameters. The time it takes for a substrate to achieve its full properties depends on its type, characteristics, and the conditions during the curing process.

Priming is a crucial step in preparing the substrate, as it plays a significant role in ensuring the waterproofing coating adheres properly and the entire protection system is effective. The purpose of priming is to: - Increase the adhesion of the waterproofing. - Prevent the substrate from dusting. - Equalize and reduce the absorbency of the substrate. Priming allows for the uniformity of the substrate's parameters. This lets the product dry evenly and achieve the same parameters everywhere.

The NEXLER Penetrator G7, a solvent-based bituminous mass, works very well as a primer for weldable felt. Like weldable roofing felt, it is modified with SBS (Styrene-Butadiene-Styrene), penetrates deeply into the substrate, and dries very quickly — in about 30 minutes at 23°C. Please note that solvent-based bitumen masses must not be used indoors. For waterproofing floors where weldable bitumen felts are used, it is recommended to use dispersion bitumen masses such as NEXLER BITFLEX Primer.

You should perform each step only after the previous layer has dried. Before proceeding to the next task, ensure that the layer is completely dry across its entire surface and throughout its cross-section. The time required between applying individual layers is specified in the product's data sheet. For single-component masses such as NEXLER BITFLEX 1K and NEXLER BITFLEX 1KP, the waiting time is approximately 6-8 hours, and for two-component masses like NEXLER BITFLEX 2K and NEXLER BITFLEX 2KP, it is approximately 4-5 hours.

Based on the soil and water conditions and the depth of the foundation, you should choose the appropriate thickness for the insulating layer. An adequate layer of NEXLER BITFLEX series mass is applied to a properly prepared and primed substrate using a trowel or a suitable spraying device (when spraying, a single layer should not exceed 3 mm in thickness). It's recommended to apply the waterproofing in at least two separate operations. Detailed instructions on preparing the substrate, preparing the product, and executing the work are available in the product's technical data sheet.

The layer thickness should be verified by checking the material consumption on a specific surface area. Additionally, it's a good practice to measure the thickness of the freshly applied sealing layer with special depth gauge plates, and the spot where the measurement was taken should be filled in immediately afterward. Once dry, a properly applied coating should form a uniform, clean layer without any flaking or other defects. The coating should adhere tightly to the primed substrate.

It depends on whether the coating is freshly applied and still completely wet, as well as how heavy the rainfall is. This risk should be considered when planning the work, and the area where the coating is to be applied should be appropriately protected. The coating achieves its full properties only after it has set. A freshly applied coating must be protected from intense sunlight (e.g., by shading), flooding, rain, and freezing temperatures. Rainwater must not be allowed to penetrate the partition and get underneath the waterproofing layer from the ground side. Rain can destroy the coating's structure, cause inconsistencies, disrupt the drying process, and reduce the final coating's overall effectiveness.

NEXLER offers a wide range of products for gluing polystyrene boards. To adhere polystyrene boards to waterproofing made of dispersion bituminous compounds, you can use the following bituminous adhesives: * NEXLER WL (for expanded polystyrene, or EPS) * NEXLER Styrbit 2000, NEXLER WK, NEXLER BITFLEX 1KP, NEXLER BITFLEX 2K, and NEXLER BITFLEX 2KP (for both EPS and extruded polystyrene, or XPS) * NEXLER STYROPUK Foundation polyurethane foam (for both EPS and extruded polystyrene, or XPS) However, be aware that polyurethane foams should only be used in ideal ground and water conditions, where the groundwater level never rises above the building's foundation. You should not glue polystyrene boards directly onto mineral adhesives for bituminous waterproofing, as they will not adhere properly to the coating and could cause damage.

Backfilling the trench is permitted 2-3 days after the waterproofing is complete, but no later than 3 months after that. If thermal insulation has been glued on, the trench can be backfilled after 3-7 days, once the mass has achieved its full adhesive properties.

We do not recommend leaving the waterproofing uncovered over the winter, as prolonged exposure to harsh weather conditions, including rain, snow, frost, and UV rays, could lead to the degradation of the waterproofing.

No, you should not use any solvent-based asphalt products indoors. Depending on the application location and use, we offer products for interior applications, such as our water-based bitumen products Water-based products are a safer option for enclosed spaces because they don't emit harmful fumes or strong odours.

NEXLER PREMIUM PYE PV250 S53H NEXLER PREMIUM: The brand name, indicating a high-quality product line. PYE: Identifies the type of bitumen used. This indicates a polymer-modified bitumen that has been enhanced with SBS (styrene-butadiene-styrene). This makes the felt highly flexible and durable, especially in low temperature. PV: Specifies polyester reinforcement with the weight of the polyester fabric in grams per square meter [g/m²], which determines its strength. S53: Denotes the thickness of the felt. The number represents the thickness in millimetres multiplied by 10. For example, S53 means the felt is 5.3 mm thick. H: A marking for a top-layer membrane. This felt is designed to be the final, uppermost layer of a multi-layer roofing system. BIT: Refers to oxidized felt. This type of felt is more rigid and less flexible than polymer-modified felts and is typically rated for a minimum flexibility of 0°C. V60: This felt is reinforced with a 60 g/m² glass fibre base, which provides stability and dimensional strength. G200: This felt is reinforced with a 200 g/m² glass fabric base. SP: Indicates a self-adhesive roofing felt. This means it can be installed without a torch, which simplifies the application process. Al: Signifies that the felt has a composite core that includes an aluminium foil layer.

Priming ensures the felt adheres properly to the substrate. It works by binding any remaining dust, penetrating the surface, and accelerating the heat-welding process for a stronger, more reliable bond.

The recommended solution depends on the roof's slope and intended use: - For roofs with a slope of 2–15%: Use a self-adhesive backing felt (e.g., NEXLER Plan PYE G200 S30 SP) that is also mechanically fastened at the seams, followed by a torch-on top-layer bituminous felt (e.g., NEXLER PREMIUM PYE PV250 S53H). - For roofs with a slope greater than 15%: Use a self-adhesive backing felt(e.g., NEXLER stick) that is mechanically fastened on the seams, followed by a torch-on top-layer bituminous felt (e.g., NEXLER PJ PYE PV250 S52H) that is also mechanically fixed at the seams. - For roofs with a slope greater than 5°: A self-adhesive top-layer felt (e.g., NEXLER top S42 SP) that is mechanically fixed at the seams is recommended. - For roofs with a slope above 12.5° (22%): Use NEXLER membrane Optimax PV as a base layer for shingles, roof tiles, or metal roof tiles. - For roofs with a slope above 20° (36.4%): A single-layer NEXLER asphalt roofing felt (Super Roof 20) can be used.

No, direct welding of felt to wooden boards is not permitted. When installing roofing felt on a wooden deck, the felt is laid loosely and mechanically fastened at the seams. These seams must then be sealed. You can do this either by gluing them with a roofing sealant or by using self-adhesive felt. For weldable roofing felt, the seams must be heat-welded. This makes it essential to protect the surface of the boards from the torch’s flame. To do this, the boards can be protected by installing a traditional felt with a glass fibre base (e.g., NEXLER P64/1200) or by using a protective strip like NEXLER Fundament 33 cm specifically under the seams.

When you choose pre-felted polystyrene boards, it's important to remember that the felt layer glued to them at the factory is not a waterproofing layer. It's only meant to provide a base for welding the final waterproofing membrane. This factory-applied felt is usually an oxidized felt with poor properties, and the installation method typically prevents a proper seal at the joints between the boards. To create a two-layer roof covering — which is recommended for residential buildings, for example — you would still need to add two additional layers of roofing felt. We believe a more effective and often cheaper solution is to start with clean polystyrene boards. You can then cover them with a self-adhesive underlayment (like NEXLER Stick) and a weldable top-layer roofing felt (like NEXLER PREMIUM PYE PV250 S53H).

Like all types of felt, self-adhesive felts must be installed according to the specifications in the product's Technical Data Sheet. Self-adhesive felts typically require a higher installation temperature than weldable or traditional felts. A higher temperature is required to properly activate the self-adhesive properties. For example, the NEXLER Top S42 SP should be applied at temperatures above +15°C. If the temperature is lower, the felt must be thermally activated with a hot air welder or a torch. It's also especially important to ensure the substrate is completely dry, as self-adhesive felts are more sensitive to moisture than other types of felt.

We do not recommend diluting our products. Using a solvent mixture different from what was used in production can change the product's properties, potentially affecting its performance and durability.

For sealing penetrations like chimneys or ventilation pipes, our main recommendation is a single-component polyurethane-bitumen resin, NEXLER Connect, used together with NEXLER Connect sealing tape. Alternatively, you can also use high-quality weldable and self-adhesive membranes for sealing.

NEXLER Cold Binder is specifically recommended for traditional roofing felts. Weldable felt should be installed by heat-welding without using any additional binder. All seams and connections to the substrate should be sealed using the melted bitumen from the felt itself.

The recommended seam widths are specified in the technical data sheet for each product. Standard felts used in multi-layer systems should have a minimum seam width of 8 cm for longitudinal overlaps and at least 12 cm for transverse overlaps. For single-layer felt, the seams should be wider, with a minimum of 12 cm for a longitudinal overlap and at least 15 cm for a transverse overlap.

Yes, on surfaces without thermal insulation, you can use two layers of self-adhesive felt: a base layer and a top layer. However, they must be installed in suitably high temperatures or with additional thermal activation, such as with a hot air welder or a torch.

The direction you lay the felt depends on the roof's slope: - For slopes less than 10%: Lay the felt across the slope (parallel to the gutter). - For slopes greater than 10%: Lay the felt along the slope (perpendicular to the gutter). Keep in mind that specialty felts often have their own specific guidelines for the laying direction, so always check the product's instructions.

There is no set maximum number of felt layers. If the existing layers are in good condition and firmly adhered to the substrate, you can apply a new layer of felt on top for renovation. Just remember that each new layer adds more weight to the roof structure, though this is generally not a concern with 5–6 layers of felt.

Yes, asphalt roofing felt can provide reliable waterproofing for a roof where you plan to install solar panels. For this kind of project, we recommend using a high-quality, torch-on top-layer bituminous felt, such as NEXLER Protection, NEXLER PREMIUM PYE PV250 S53H, or NEXLER One. These felts can be used with an underlayment to create a two-layer roofing system for both new and existing roofs where solar panels are planned.

A melt that is too wide affects the roof's appearance but should not compromise its watertightness. To improve the aesthetics, the excess asphalt can be sprinkled with grit immediately after welding.

The recommended installation temperature for membranes is 0°C for Styrene-Butadiene-Styrene modified felts and +5°C for low-modification and oxidized felts. This temperature requirement applies to both daytime and nighttime and to the temperature at which the felt was stored for the 24 hours prior to installation. You can apply felt at temperatures lower than recommended, but only if you take precautions. For example, store the felt rolls in a heated room (at least +18°C) for 24 hours before installation. If the felt cracks during application, you must stop the installation, as the cracked felt may not remain watertight. Also, regardless of the ambient temperature, the felt must always be applied to a dry and frost-free surface. You should never install felt during rain, snow, or strong winds, as these conditions prevent proper welding. To ensure better conditions, you can protect the work area with a tarpaulin, for instance.

It's generally impossible to completely eliminate water pooling on roofs with a slope below 3° (5%). However, it is acceptable as long as the stagnant water can evaporate and the pools aren't too deep. For two-layer roofing systems, the maximum allowed depth for water pools is 1 cm.

When properly installed, highly modified roofing felts can guarantee a watertight roof for at least a decade or even several decades. During this time, the felt typically requires no renovation. Older bituminous roofs, such as those made with oxidized felt, may require renovation, but this is less common with modern materials. The parts of the roof that most often need maintenance are the vertical flashings, such as the seals on pressure strips. These typically need to be resealed about every two years.

In mechanically fixed systems, the felt is usually fastened to the structural deck with telescopic connectors, which are placed under the seams of the underlayment. The connector is mounted on the underside of the overlapping felt, about 1 cm away from its edge. It's then covered by the next strip of felt. You must use telescopic connectors to fix the felt to the thermal insulation. Rigid fasteners may cause perforation of the covering. For low-rise roofs up to 12 meters high, an adhesive system can be used instead of mechanical fasteners. This method requires gluing the boards with adhesives designed for that specific insulation type and then bonding the underlayment to the insulation boards—for example, by gluing self-adhesive felt onto EPS boards or welding heat-sealable felt to primed mineral wool.

To maintain old roofing felt, we recommend using the bituminous agent NEXLER Reno Bit or applying a protective and decorative layer of NEXLER Silver Protect or NEXLER Isofol Roof. When using NEXLER Reno Bit, you should apply a layer of grit to the newly laid coating.

A large number of blisters usually indicates that water is trapped between the old felt layers. On hot days, this water heats up, turns into steam, and causes the blisters to form. Welding standard felt directly over these blisters may cause them to reappear on the new felt. Therefore, if your old roof has many blisters, you should consider using a special ventilation felt, such as NEXLER Renovation. This felt has special bitumen strips on the underside that allow for partial welding, creating a network of channels beneath the surface. Water vapour can then migrate through these channels to ventilation openings, allowing the roof to dry out. Before welding the ventilation felt, the old covering must be repaired, primed, and then drilled or cut to facilitate moisture evaporation.

No, you should not install asphalt felts over tar-based materials. It is recommended that you remove the existing tar paper completely and install a new roofing system with asphalt felt.

The smaller strip of foil, located near the top edge of the shingle, is designed to help you more easily remove the larger foil sheet that covers the entire surface. You don't need to remove it. The only time it's recommended to remove the small strip is when you're installing the starting strip of shingles, as they are laid upside down, and removing the foil helps the shingles adhere more effectively.

We do not offer specialized ridge shingles. Instead, they should be cut from standard shingle sheets. A cutting diagram is provided in the shingle installation instructions included in every package of shingles.

There is no vulcanization process involved with these shingles. Instead, they are typically glued together on the roof, which provides extra sealing and a more secure attachment. NEXLER shingles have excellent adhesive properties. However, the gluing process depends on a variety of factors and doesn't always happen. The primary protection for the shingles against wind uplift comes from mechanical fastening with roofing felt nails and using purpose-specific bituminous agents to glue the shingles in the edge and corner zones.

In wet rooms, you should pay close attention to corners, wall edges, pipe penetrations, and where deformable and non-deformable surfaces meet, such as wall-to-wall and wall-to-floor connections. These areas need to be protected by embedding sealing tapes, like NEXLER Sealing Tape 120/120, into the waterproofing under the slab, or by using sealing sleeves for pipe penetrations.

Yes, both NEXLER Izofol Flex and NEXLER Izofol are perfect for underfloor heating systems because of their flexibility and resistance to high temperatures. However, you must follow all the heating manufacturer's recommendations.

Yes, the internal waterproofing created with the semi-liquid NEXLER Isofol Flex film can be painted with acrylic paints. In fact, it serves as an excellent primer for them.

Yes, these products are an excellent base for ceramic tile adhesives. You can begin laying ceramic tiles approximately 24 hours after the final layer of internal insulation has been applied. Ceramic tiles can be laid with any highly elastic adhesive recommended by the tile manufacturer.

NEXLER offers the NEXLER RENOBUD R repair system, which is designed specifically for fixing damaged concrete structures. Before you begin any repairs, you must properly prepare the surface. The extent of this preparation depends on the damage, its location, and your planned repair method. For minor damage, local chipping with chisels and hammers might be enough. If there is surface corrosion, the damaged concrete layers should be ground away (or, less often, milled). After this, thoroughly vacuum or pressure-wash the chipped/sanded surfaces. If the concrete is so deteriorated that rebar is exposed, first clean it (to Sa 2 grade) and then cover it with NEXLER RENOBUD R 102. Once the rebar is protected, you can begin to repair the defects and reprofile the slab. For reprofiling, use the appropriate repair mortar - NEXLER RENOBUD R 103 for defects 10 to 50 mm thick, or NEXLER RENOBUD R 105 for gaps 3 to 10 mm thick. To ensure the repair layer bonds securely and creates a single, solid piece, you must first apply a bonding layer of NEXLER RENOBUD R 102. It's crucial to apply the repair layer to the bonding layer while it's still wet, following the “wet on wet” principle. For a smooth finish, you can complete the repair with a levelling putty — NEXLER RENOBUD R 105 — applied in a layer 3 to 10 mm thick. If the terrace slab lacks a proper slope, you must create one. The terrace slope should be 1.5-2% to ensure water drains freely. When the thickness of the terrace layers is limited, you can use mortars to create the slope. The thinnest point of this profiling layer is limited only by the diameter of the grains in the mortar. However, a concrete slope layer must have a minimum thickness of 3.5 cm at its thinnest point.

A vapour barrier on a terrace is a crucial layer that prevents warm, moist air from the building's interior from reaching a cold surface and condensing. A terrace is a structural element exposed to significant temperature differences, especially during the winter. Warm air from inside the building is constantly trying to move through the terrace slab toward the cold air outside. Without a barrier, this warm vapour would reach the cold waterproofing layer, cool down to its dew point, and turn back into liquid water. This condensation collects under the waterproof membrane, leading to damp spots. This can often create the false impression that the terrace itself is leaking when the real problem is moisture from the inside. Vapour Barriers for Terraces: What We Recommend NEXLER Alu S40.

The waterproofing layer protects the substrate from moisture and, because it's flexible, it can handle thermal displacement without cracking. You can apply ceramic tiles directly to the NEXLER AQUAMINERAL 2K Ultra two-component sealing micro particle mortar. The NEXLER AQUAMINERAL 2K Ultra can be applied using a brush, trowel, or spray device. It's crucial to rub the first thin layer in with a brush to seal any pores in the surface. Wait for a technological break of 3 to 4 hours between coats to allow each layer to dry properly. Each layer should be about 1 mm thick, and no more than 2 mm. After roughly 24 hours, you can lay ceramic tiles using C2 class mineral adhesives. For about 12 hours while it cures, protect the coating from rain, frost, rapid water evaporation, and extreme temperature changes. Special attention is needed when preparing the substrate at the joints between vertical elements and the terrace floor. These surfaces move differently from one another, and the resulting stresses are concentrated in the corners. NEXLER Sealing Tape should be embedded in all corners.

The best way to seal a door threshold depends on a few things – the design of the door, whether it's an interior or exterior wall, the type of waterproofing used, and the kind of door frame. When using a micro particle mortar like NEXLER AQUAMINERAL 2K Ultra for waterproofing, we recommend using a sealing tape that has a self-adhesive butyl strip. If you used roofing felt for your waterproofing, you should seal the threshold with a self-adhesive felt, such as NEXLER Membrana SP. No matter which waterproofing material you used, we suggest a new product from our lineup: NEXLER Connect with NEXLER Connect Tape.

Finishing a balcony with ceramic tiles is one way to create a bonded surface, but a floating system on joists or pads is a great alternative. You can also finish a balcony slab with: - Epoxy or polyurethane resin - Concrete slabs - Micro-screed - Paint and anti-slip coating - Outdoor vinyl tiles - Rubber or PVC granulate mats - Composite or wooden decking on joists

When installing a floating system, the balcony's structural slab should first have a proper slope of 1.5-2% and be waterproofed. We recommend either insulating with a 3 mm layer of NEXLER AQUAMINERAL 2K Ultra micro particle mortar or by applying two layers of NEXLER PREMIUM PYE PV200 S40 and NEXLER PREMIUM PYE PV250 S53H weldable membrane. If you use the membrane, you must first prime the substrate with NEXLER BITFLEX Primer bituminous preparation. For a floating deck, install the joists along the balcony's slope. You can also use structural supports instead of joists, which come in both adjustable and non-adjustable versions. Adjustable supports are especially useful for creating a perfectly level surface. Always remember to protect the waterproofing layer from being damaged by the joists or supports.

The method to use depends on the type of waterproofing. - For micro particle mortar: Place a high-density, non-woven fabric (like Nexgreen Geo Safe 350) under the joists or pads. - For insulating felt: We recommend using protective pads made of top-layer felt. These materials will ensure your insulation is effectively protected and remains durable.

Tiles can be glued to insulation that serves as a mineral-based substrate, such as NEXLER AQUAMINERAL 2K, NEXLER AQUAMINERAL 2K Ultra, or NEXLER Izofol Flex.

The production date and expiration date are located on a sticker on the packaging, typically on the lid.

Weldable roofing felt does not require maintenance throughout its service life.

No, NEXLER solvent products are ready-to-use. We do not recommend diluting these products.