Soudal Silirub 2 - Premium Low Modulus Neutral Silicone

Health & Safety Recommendations

Read the product label and Safety Data Sheet before use and follow normal site hygiene and safe working practices. Keep the area well ventilated during application and throughout curing, particularly in enclosed spaces such as bathrooms, plant rooms and glazing workshops.

Wear suitable gloves and eye protection and avoid prolonged skin contact, especially when smoothing or cleaning. If sealant contacts skin, wash with soap and water. If it contacts eyes, rinse carefully with clean water and seek medical advice if irritation persists. Keep cartridges out of reach of children and away from food preparation areas, and dispose of empty cartridges, masking tape and contaminated wipes in accordance with local regulations

Substrate Suitability

Soudal Silirub 2 is a low modulus, neutral cure silicone sealant designed for building joints and glazing where high movement and reliable weather sealing are required. It adheres well to many common construction materials including glass, ceramic tiles, concrete, metals, anodised aluminium, stainless steel, lacquered wood and many PVC profiles.

For glazing and façade work it is widely used for perimeter sealing between uPVC, treated timber or metal frames and glass, and for general construction joints subject to temperature cycling, wind load and vibration. Silirub 2 is not suitable for PE, PP, PTFE (Teflon®) or bituminous substrates, and it must not be used on natural stone such as marble or granite where staining can occur.

It must not be used on polycarbonate, where Silirub PC should be used instead, and it is not suitable for aquarium bonding where Silirub AQ is required. It is also not intended as a structural glazing adhesive.

Surface Preparation

Correct preparation is essential for long-lasting silicone joint performance. The joint edges must be rigid, clean, dry and free from dust, laitance, loose coatings, oil, grease and release agents. Non-porous substrates such as glass, metals and many plastics should be cleaned and degreased using Soudal Cleaner & Degreaser, then wiped dry with a clean, lint-free cloth before sealing.

Porous substrates should be sound and stable, with weak material removed; where improved adhesion is required, prime porous surfaces using Soudal Primer 150 in line with primer guidance and site conditions. Because substrate finishes and coatings vary widely, an adhesion and compatibility test should always be carried out before full application, particularly on painted or powder-coated metals, coated glass, unusual plastics, or where the joint will be exposed to extreme weather, high water loading or aggressive cleaning regimes.

Application Method

Mask the joint edges with Masking Tape if a crisp finish is required, then ensure the joint is correctly designed and backed to control depth. Cut the nozzle to suit the bead size and fit the cartridge into a caulking gun.

Apply Silirub 2 steadily, keeping the nozzle in contact with the joint and filling the cavity evenly to avoid air inclusions. For best results, apply in one continuous pass and maintain a consistent bead profile along the full joint length, paying close attention at corners, mitres, terminations and frame junctions where movement is often concentrated.

Tool the sealant before skin formation to compact it against the joint flanks and create a smooth, weather-shedding surface. Use a suitable spatula and a light soapy solution to aid finishing, but prevent the soapy solution from contacting the adhesion surfaces, as this can cause local loss of adhesion.

Only dip the finishing tool into the soapy solution rather than spraying it into the joint. Avoid finishing in full sunlight where the soapy solution can dry too quickly and mark the surface. Remove masking tape immediately after tooling, while the sealant is still workable, to avoid tearing the bead edge.

Joint Dimensions

Silirub 2 is suitable for joints designed to accommodate movement, with a maximum allowed joint movement of ±25% when correctly specified. Joint dimensions should be maintained within the practical limits of the product and the construction detail: a minimum joint width of 5mm, a maximum joint width of 30mm, and a minimum joint depth of 5mm.

As a general rule for sealant joints, the recommended relationship is joint width = 2 x joint depth, helping maintain the correct bead geometry for movement, durability and adhesion. Use a PE backer rod in deeper joints to control depth and prevent three-sided adhesion, which can restrict movement and increase stress on the bond line.

Coverage

Coverage depends on joint width and depth, and on the consistency of the bead applied. For a reliable estimate of how many cartridges are required for a given joint size and total run length, use the Platinum Chemicals Sealant Estimate Calculator, which provides guidance based on typical joint dimensions and standard cartridge volumes.

Curing Time

Silirub 2 cures by moisture curing. Skin formation occurs in approximately 9 minutes, and curing proceeds at approximately 2mm per 24 hours, with the exact rate influenced by temperature, humidity, ventilation and joint geometry.

Lower temperatures, low humidity, limited airflow and deep joints will slow curing, while warmer, well-ventilated conditions usually accelerate it. Protect freshly applied joints from rain and contamination during the early curing stage, and avoid stressing the joint, washing the area, or exposing it to aggressive cleaners until the sealant has cured sufficiently through its thickness.

Cleaning

Clean up immediately after application. Uncured Silirub 2 can be removed from tools and adjacent non-porous surfaces using Soudal Swipex Wipes. Once cured, silicone cannot be dissolved and must be removed mechanically, with residue and smear removal supported using Soudal Silicone Remover Gel or Soudal Sealant Remover Spray in accordance with their instructions.

Keep cleaning materials and finishing aids away from the joint edges before sealing, as any contamination of the adhesion surfaces can reduce bond strength. Always test cleaners on sensitive finishes, plastics and coatings before wider use.

Limitations

Silirub 2 is not paintable, so it should be specified where a permanent silicone finish is acceptable. Do not use on natural stone due to staining risk. Do not use on bituminous substrates or on PE, PP and PTFE (Teflon®).

Do not use where continuous water immersion is possible, and do not use as a structural glazing adhesive. Avoid contact with bitumen, tar and plasticiser-releasing materials such as EPDM, neoprene and butyl, as this can lead to discolouration and loss of adhesion; where sealing to EPDM is required, use Silirub EPDM.

Do not use on polycarbonate, where Silirub PC is required. When applying multiple reactive sealants in one area, ensure the first sealant is completely hardened before applying the next. Any colour change, discolouration or surface ageing can be influenced by chemicals, heat and prolonged UV exposure, and a total absence of UV can cause colour change in some environments.

Other Information

Silirub 2 is a thick-bodied, neutral cure silicone with very low modulus behaviour, supporting durable weather seals and movement joints in glazing, façade and general building applications. Because curing is moisture-driven, maintain ventilation during curing and avoid sealing over wet, unstable or contaminated surfaces.

Mask adjacent areas where appearance matters and avoid spilling sealant onto visible finishes; using tape beside the joint is an effective way to prevent smearing on surrounding substrates. Once opened, the product has a limited shelf life, so store cartridges properly and use opened product promptly to maintain consistent gunning and curing behaviour.

Q) What is Soudal Silirub 2 and what is it designed to do?

A) Soudal Silirub 2 is a premium, low modulus, neutral cure silicone sealant designed for professional building and glazing work where long term elasticity and weather resistance are essential. It is a 100% silicone, so it cures without shrinkage and stays permanently flexible, making it suitable for high movement perimeter joints and expansion joints. It is independently tested to ISO11600 F&G 25LM and offers ±25% movement capability, which is the key reason it is specified on façades and glazing lines. It guns cleanly, tools well, and often adheres without primer to many common substrates such as glass, metals, masonry and timber.

Q) What does low modulus mean on Soudal Silirub 2, and why does it matter?

A) Low modulus means the cured sealant remains softer and more elastic, so it can stretch with joint movement while putting less stress on the joint edges. That matters on frames, façade junctions and expansion joints because building materials move differently with heat, wind load and settlement. A higher modulus sealant can pull harder on the bond line, which increases the risk of edge tearing or de bonding over time. Soudal Silirub 2 is designed for movement, with ±25% capability and very high elasticity, so it is better suited to joints that cycle repeatedly rather than joints that stay largely static. Correct joint design still matters for durability.

Q) Where is Soudal Silirub 2 most commonly used on buildings?

A) Soudal Silirub 2 is commonly used for perimeter sealing around window and door frames, façade panel junctions, and high movement construction joints where a durable weather seal is needed. It is also used in glazing related sealing, including many professional building and glazing applications where the joint must remain watertight and airtight for years. Because it resists UV and weathering extremely well and stays flexible over a wide temperature range, it suits exposed exterior joints where lesser sealants can chalk, crack or harden. It is also used on roofline and drainage related sealing details, and on building services joints where vibration and thermal change are common.

Q) Can Soudal Silirub 2 be used for glazing and window frame perimeter sealing?

A) Yes, Soudal Silirub 2 is designed for glazing and perimeter sealing where long term elasticity and weather resistance are required. It adheres well to glass and is widely used to seal between glass and frame materials such as aluminium, uPVC and treated timber, as well as to adjacent masonry where joint movement and exposure are expected. Its ISO11600 G 25LM classification supports its suitability for glazing joints, and the low modulus behaviour helps cope with seasonal movement without stressing the bond line. Always follow good glazing practice, ensure correct joint dimensions and depth control, and carry out compatibility checks when the silicone will be close to insulating glass edge seals or laminated glass components.

Q) What substrates does Soudal Silirub 2 typically bond to without primer?

A) Soudal Silirub 2 is designed to offer primerless adhesion to many common substrates, which can simplify installation on site. Typical examples include glass, many metals, masonry, and timber, plus many plastics used in building profiles. Actual primer need depends on surface condition, coating type and exposure level, so a small adhesion test is sensible when working on painted or powder coated metals, unusual plastics, coated glass, or repaired masonry with variable absorbency. Cleanliness is critical, especially on non porous surfaces where release agents, polish or airborne contamination can cause edge failure. If adhesion is uncertain or the substrate is porous and inconsistent, using Soudal Primer 150 can improve reliability.

Q) Is Soudal Silirub 2 compatible with double glazed units and laminated glass?

A) Soudal Silirub 2 is intended for glazing and building joints and can be used with most types of glass, but it is not suitable for self cleaning glass. Internal testing indicates compatibility with most insulating glass unit edge seals and conventional PVB films used in laminated glass, which is helpful for wet glazing and perimeter sealing. However, there is no universal guarantee because glass manufacturers change edge seal systems and laminated constructions over time. For that reason, a project specific compatibility test is recommended whenever the silicone will be close to edge seals or laminate interlayers, especially where appearance, warranty and long term performance are critical. This is normal best practice in professional glazing work.

Q) What is the movement capability of Soudal Silirub 2 in real terms?

A) Soudal Silirub 2 offers ±25% movement capability when correctly designed and installed, meaning the joint can expand or contract significantly relative to its original width without the seal tearing or losing adhesion. This is why it suits high movement perimeter joints and expansion joints on façades and frames. It also has very high elasticity, with elongation at break greater than 800%, which helps it cope with repeated cycles of movement and vibration. Movement performance depends heavily on joint geometry, correct depth control and proper two sided adhesion. Using a backer rod to prevent three sided adhesion and maintaining the right bead shape makes a practical difference to long term durability.

Q) How quickly does Soudal Silirub 2 skin and how fast does it cure?

A) Soudal Silirub 2 has fast skin formation at around 9 minutes, which supports quick tooling and helps reduce early contamination from dust and airborne dirt on exposed joints. It cures by moisture, and the typical curing rate is around 2mm per 24 hours, but this varies with temperature, humidity, airflow and joint dimensions. Deep joints cure more slowly, and cold or very dry conditions can delay through cure. The sealant should be protected from heavy rain, washing and early mechanical stress during the initial curing period. For critical external joints, allow adequate curing time before exposing the joint to aggressive cleaning, water loading or movement.

Q) What joint sizes are suitable for Soudal Silirub 2?

A) Soudal Silirub 2 is typically used in joints with a minimum width of 5mm and a maximum width of 30mm, with a minimum depth of 5mm. For movement joints, bead geometry matters as much as width, because too deep a bead can restrict movement and slow curing, while too shallow a bead can tear at the edges. A common approach is to design joint width around twice the joint depth, then control depth using a PE backer rod so the sealant bonds to two sides only. This encourages correct movement behaviour and reduces stress on the bond line. Always follow the joint design within the construction detail and exposure requirements.

Q) How should surfaces be prepared before applying Soudal Silirub 2?

A) Joint edges must be clean, dry, rigid and free from dust, loose coatings, oil, grease, release agents and weak surface layers. On non porous substrates such as glass and metals, clean and degrease properly, then wipe dry with a lint free cloth so you are not leaving a solvent film behind. On porous substrates such as masonry, remove friable material and ensure the edge is stable, because the sealant will only perform as well as the surface it is bonded to. Masking the joint edges helps produce a crisp finish. If a primer is required, apply Soudal Primer 150 to the bonding faces only and allow it to dry as instructed before sealing.

Q) What is the best application method for Soudal Silirub 2 on a façade or frame joint?

A) Use masking tape if a clean line is required and ensure a backer rod is installed where depth needs controlling. Cut the nozzle to suit the joint size and gun the sealant in a steady, continuous bead, keeping the nozzle in contact with the joint so the sealant wets both sides fully and avoids trapped air. Aim for consistent bead shape along the full run and take extra care at corners, mitres and terminations where movement and stress often concentrate. Tool before skin formation to compact the sealant against the flanks and create a smooth weather shedding profile. If using a light soapy solution to aid tooling, keep it off the adhesion surfaces and remove tape immediately.

Q) Do you need a backer rod when using Soudal Silirub 2?

A) A backer rod is strongly recommended for deeper joints because it controls sealant depth and prevents three sided adhesion, which can restrict movement and increase stress on the bond line. With high movement sealants like Soudal Silirub 2, correct joint design is essential to get the full benefit of ±25% movement capability. The backer rod also helps you achieve a consistent bead profile and can reduce product usage by avoiding excessive depth. Use a suitable closed cell PE backer rod sized so it sits firmly without being compressed too aggressively. The goal is to support a two sided bond with a flexible, correctly proportioned bead that can stretch and recover during movement cycles.

Q) Is Soudal Silirub 2 paintable once cured?

A) No, Soudal Silirub 2 is not paintable in a reliable way, which is typical for high performance silicones. Many paints will not adhere properly to silicone, and even if a paint film appears to stick, it can crack or peel as the sealant moves. If you need a paintable joint, you should select a sealant type designed for painting rather than relying on overcoating silicone. With Silirub 2, the best approach is to choose the correct sealant colour for the application and focus on neat finishing, masking and consistent tooling. On visible glazing lines and façade joints, a crisp bead and correct joint profile usually gives the best long term appearance.

Q) What weather and UV resistance can you expect from Soudal Silirub 2?

A) Soudal Silirub 2 offers excellent resistance to UV and weathering, which is one of the main reasons 100% silicone is specified for exposed exterior joints. It remains stable in rain, snow and typical building exposure conditions and is designed to resist ageing that can cause cheaper sealants to harden, chalk or crack. It also has a very wide service temperature range from -60°C to +180°C once cured, so it copes well with intense solar gain, cold snaps and repeated temperature cycling. Good performance still depends on correct application, as poor surface preparation, incorrect joint geometry or contamination during tooling can undermine durability regardless of the sealant grade.

Q) What are the key technical points people should know about Soudal Silirub 2?

A) The key technical points are that Soudal Silirub 2 is a neutral cure, low modulus, 100% silicone that cures without shrinkage and remains permanently elastic. It is independently tested to ISO11600 F&G 25LM and offers ±25% joint movement capability. It skins fast at around 9 minutes and cures at roughly 2mm per 24 hours, with curing influenced by moisture, temperature and airflow. It has very high elasticity with elongation at break above 800%, helping it cope with repeated movement. It is MEKO free, which supports modern specification requirements. It is not paintable and is not intended for natural stone due to staining risk.

Q) Can Soudal Silirub 2 be used for roofing, lead and fibre cement sealing?

A) Soudal Silirub 2 is commonly used for durable exterior sealing in roofline and weather exposed details where flexibility and UV resistance are important, and it is listed as suitable for sealing interfaces involving lead and fibre cement in roofing type applications. The benefit is that it stays elastic and resists weathering over time, which helps prevent cracking at joints that experience thermal cycling and vibration. As with any roofing detail, success depends on correct joint design and sound substrates. Ensure surfaces are clean and stable, and avoid sealing onto bituminous materials or contaminated edges. If the joint is subject to constant water immersion or is part of a specialist roofing system, follow the system guidance and carry out suitability checks.

Q) What should you avoid bonding or sealing with Soudal Silirub 2?

A) Avoid PE, PP and PTFE because adhesion is unreliable. Avoid bituminous substrates and any surface that is oily, dusty or unstable, because the sealant will only hold as well as the layer beneath. Do not use Soudal Silirub 2 on natural stone such as marble or granite due to staining risk, and do not use it on polycarbonate where a dedicated polycarbonate silicone is required. It is not suitable as a structural glazing adhesive, so it should not be used where the sealant line is expected to carry structural loads. Also be careful where the silicone could contact materials that can cause discolouration or adhesion loss, such as some rubber types and plasticiser releasing products.

Q) Is Soudal Silirub 2 suitable for bathrooms and kitchens?

A) Soudal Silirub 2 can be used in wet areas where a neutral cure, high movement silicone is useful, such as around frames, trims or glazing in bathrooms and kitchens, but it is not a dedicated sanitary mould resistant product. If the priority is strong mould resistance around baths, showers and sinks, a sanitary grade silicone designed for that purpose is typically the better choice. Silirub 2 is more commonly selected for building envelope and glazing type joints where weathering, movement and long term elasticity are critical. In wet rooms, preparation still matters, and the joint should be left to cure properly before exposure to water. Choose the product based on the real demand of the joint rather than using one sealant for every scenario.

Q) How do you calculate coverage for Soudal Silirub 2?

A) Coverage depends on joint width and depth, and the total metres you can seal per cartridge changes significantly between a slim perimeter bead and a deeper expansion joint. A practical way to estimate is to measure the joint dimensions you intend to use, then use a sealant calculator based on cartridge volume to convert cross sectional area into metres of run. On site, also allow for waste from nozzle trimming, bedding, and any over tooling. If the joint edges are irregular, consumption increases because more sealant is needed to fill voids properly. Avoid under filling to stretch coverage, because thin sections reduce movement capability and can lead to early edge tearing or failure.

Q) What is the best way to clean up Soudal Silirub 2 during and after use?

A) Clean up is simplest while the sealant is uncured. Use suitable wipes for fresh residues and keep cleaning cloths away from the adhesion faces before gunning, because contamination can compromise bond quality. Masking tape is one of the easiest ways to prevent smearing on adjacent finishes, especially on glass, aluminium and coated panels. Once cured, silicone must be removed mechanically, and removers can help soften residues and improve clean-up, but you still need scraping to fully remove material. If you are re-sealing, remove all old silicone fully because new silicone will not bond reliably to cured silicone. Work in manageable lengths so tooling and clean-up happen before skin formation.

Q) What practical tips help get the best finish with Soudal Silirub 2?

A) The simplest way to get a crisp professional finish is to mask both sides of the joint, use the correct backer rod to control depth, and gun a steady continuous bead without gaps. Tool within the workable window before skin formation and aim for a smooth profile that sheds water, especially on exterior joints. Use a light soapy solution only on the tooling tool, not on the joint edges, because wetting the adhesion surfaces can cause local loss of adhesion. Remove masking tape immediately after tooling for a clean edge. Keep the joint protected from dust and rain during early cure and avoid stressing the joint until sufficient cure has developed, especially on deeper movement joints where through cure takes longer.

Technical Data Sheet

Declaration of Performance (DoP)

Safety Data Sheet