Fosroc Nitoseal MS100
One-part, primerless, non-staining MS polymer facade sealant with high 50% movement accommodation and fast neutral cure
What is it?
A one-part, gun-grade (non-sag) joint sealant based on hybrid silyl-modified polyether (MS polymer) chemistry. It cures by reaction with atmospheric moisture into a tough, low-modulus elastomeric seal and is engineered specifically for non-staining facade work.
Where is it used?
Movement and perimeter joints on building facades, precast and stone cladding, masonry, brickwork, fibre-cement sheeting, and around window and door frames, on both external and internal elevations.
Why use it?
It combines a high 50% movement accommodation factor with primerless adhesion to most substrates, a damp-tolerant application window, and genuinely non-staining behaviour on marble, stone and concrete, which removes the dark oily bleed associated with cheaper polyurethanes and silicones.
How is it applied?
Gun-applied from 380ml cartridges or 600ml sausages into a designed joint over a backer rod or bond-breaker tape at roughly a 2:1 width-to-depth ratio, then tooled to a smooth concave profile while still wet.
About Fosroc Nitoseal MS100
Fosroc Nitoseal MS100 is a premium single-component facade joint sealant built on hybrid silyl-modified polyether (MS polymer) technology, the same chemistry family that has largely displaced older polyurethanes and silicones in demanding architectural sealing. It sits within Fosroc’s wider Nitoseal MS range (MS60, MS100, MS300 and MS600), and MS100 is the variant tuned for stain-free sealing of natural stone, marble, precast and masonry facades. Supplied ready to use, it cures by reaction with atmospheric moisture to form a tough, flexible, low-modulus rubber seal that moves with the building rather than resisting it.
For Indian projects, MS100 answers a recurring site problem: conventional polyurethane and low-grade silicone sealants frequently bleed plasticiser into porous stone and concrete, leaving permanent dark haloes along cladding joints that are almost impossible to clean off a finished elevation. MS100 is formulated to be genuinely non-staining on marble, granite, sandstone and concrete, while still bonding without a primer to most common substrates. It tolerates damp (though not visibly wet) surfaces during application, which is valuable in monsoon-affected schedules and on freshly cured concrete, and it is isocyanate-free and low-odour, making it more comfortable for applicators and more suitable for occupied or sensitive interiors.
The headline technical property is its movement accommodation. MS100 carries a 50% Movement Accommodation Factor (MAF) and is classified to BS EN ISO 11600 as Class F25LM (a facade sealant, Class 25, Low Modulus), and to ASTM C920 as Type S, Grade NS, Class 25. It also complies with EN 15651-1 for facade-element sealants and carries an EN 140-3 acoustic rating, so it contributes to the airtightness and sound performance of the building envelope, not just water exclusion. In practical terms a high MAF means a narrower designed joint can absorb the same thermal and structural movement, which simplifies detailing on long cladding runs.
Space Arc Engineering supplies Nitoseal MS100 as an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India, and can support specification, joint design and on-site application for facade, cladding and curtain-walling packages.
The technical insight
The defining number on Nitoseal MS100 is its 50% MAF, which is double the 25% MAF of the other members of the Nitoseal MS range (MS60, MS300, MS600). That distinction matters when sizing joints. Because MAF is expressed as a percentage of the minimum design joint width, a sealant that accommodates 50% movement lets a designer achieve the same absolute movement capacity in roughly half the joint width a 25% product would need, or alternatively gives a large safety margin in a generously sized joint. For a facade with significant thermal cycling, that is the difference between a clean, narrow architectural joint and an unsightly wide one. The trade-off is that, like all MS polymers, MS100 is a non-sag elastic sealant intended for moving butt and perimeter joints, not a self-levelling pouring grade for horizontal trafficked joints, and not a structural adhesive. Its low-modulus character (the LM in F25LM) is deliberate: low stress is transferred back into weak or brittle substrates such as natural stone and aerated/precast units, reducing the risk of cohesive failure at the bond line. The neutral, isocyanate-free cure also explains the non-staining and over-paintability advantages, but means cure is moisture- and temperature-dependent, so deep joints cure progressively from the surface inward over days rather than instantly.
Where it is used
- Movement and expansion joints between precast concrete cladding panels
- Perimeter sealing around window and door frames (external and internal)
- Joints in and around natural stone and marble cladding where staining must be avoided
- Brickwork, blockwork and masonry control/movement joints
- Joints in fibre-cement and cement-board sheeting and rainscreen systems
- Curtain walling and infill panel perimeter joints
- Construction and day-work joints in facade and external wall elements
- Internal partition and dry-lining perimeter joints requiring acoustic sealing
- General weatherproofing of building-envelope joints subject to thermal movement
Key advantages
- High 50% Movement Accommodation Factor allows narrower, cleaner architectural joints for a given movement
- Genuinely non-staining on marble, granite, stone and concrete, eliminating plasticiser bleed haloes
- Primerless adhesion to most common substrates (concrete, masonry, metals, timber, many coatings), speeding application
- Single-component and ready to use, no on-site mixing or ratio errors
- Damp-tolerant during application, suiting monsoon schedules and freshly cured concrete
- Fast neutral cure, typically touch-dry within about two hours depending on conditions
- Isocyanate-free, low-odour and over-paintable, better for applicators and interiors
- Carries an EN 140-3 acoustic rating, contributing to envelope airtightness and sound control
- Compatible with residual contamination from previous PU, polysulphide and silicone sealants in remedial work
- Excellent UV and weather durability for long-life external exposure
Limitations & considerations
- Non-sag gun grade only, not a self-levelling pouring grade for horizontal floor or pavement joints
- Not intended for continuous trafficking or high hydrostatic/immersed duty, where Nitoseal MS300 or a polysulphide is more appropriate
- Not a structural or load-bearing adhesive and not a substitute for a waterstop in water-retaining structures
- Moisture- and temperature-dependent cure means deep joints cure slowly from the surface inward
- Requires a correctly designed joint with backer rod or bond-breaker to achieve the right width-to-depth ratio and prevent three-sided adhesion
- Porous substrates such as GRC may still need a primer for optimal adhesion despite the primerless claim
- Should not be applied over visibly wet, frozen or contaminated surfaces
- Colour range, while broad, is limited to standard facade tones unless minimum-quantity custom colours are ordered
Selection & best practice
Design the joint before specifying the sealant. Aim for a width-to-depth ratio of about 2:1 for facade joints (the optimum for elastic sealants), with a typical applied joint width in the 5-35mm range. Use a closed-cell polyethylene backer rod (such as Fosroc Expandafoam or Hydrocell) or a self-adhesive bond-breaker tape at the back of the joint so the sealant bonds to only two faces and is free to stretch; never allow three-sided adhesion, which causes early cohesive tearing. Size the joint width from the structure’s calculated total movement and the 50% MAF, then add margin. Ensure substrates are sound, clean, dry to damp (not wet) and free of laitance, oil and old loose sealant. Prime porous or marginal substrates such as GRC where recommended, but most concrete, masonry, metal and timber needs no primer. Apply by gun, fully fill the joint without entrapping air, then tool to a smooth concave profile while the sealant is still wet to consolidate adhesion to both faces. Mask adjacent stone for a crisp line and respect the recoat/curing window before exposure to standing water.
Specifications
| Product type | One-part, gun-grade (non-sag) elastomeric joint sealant |
| Chemistry | Hybrid silyl-modified polyether (MS polymer) |
| Cure mechanism | Neutral cure by reaction with atmospheric moisture |
| Movement Accommodation Factor (MAF) | 50% |
| ISO 11600 classification | Class F25LM (facade, Class 25, Low Modulus) |
| ASTM C920 classification | Type S, Grade NS, Class 25 |
| European facade standard | EN 15651-1 (sealants for facade elements) |
| Acoustic rating | EN 140-3 acoustic rated |
| Primer | Not required on most substrates; recommended on porous surfaces such as GRC |
| Joint width range | 5 – 35 mm |
| Width-to-depth ratio | Approx. 2:1 (facade optimum) |
| Touch-dry / skin time | Up to approx. 2 hours, depending on ambient conditions |
| Substrate condition | Dry to damp (not wet); damp-tolerant during application |
| Colours | White, Grey, Light Grey, Black, Buff, Brown, Portland Stone and others; custom colours to minimum order |
| Pack sizes | 380 ml cartridge / tube and 600 ml sausage (foil) |
| Shelf life | Approx. 12 months from manufacture in unopened packaging, stored cool and dry |
| Key features | Non-staining, primerless, isocyanate-free, low-odour, UV resistant, low modulus |
Industry use cases
Commercial and IT park facades
Sealing movement and panel joints on stone, precast and glazed elevations of office and IT-park buildings across Delhi NCR, where a non-staining seal on premium cladding is essential to the finished look.
Luxury residential and hospitality
Perimeter and cladding joints on marble and granite-clad apartment towers and hotels, where plasticiser bleed from conventional sealants would permanently mark the natural stone.
Institutional and healthcare
Window-perimeter and partition joints in hospitals, schools and laboratories that benefit from the low-odour, isocyanate-free formulation and the EN 140-3 acoustic rating.
Facade remediation and retrofit
Re-sealing existing facades where old PU, polysulphide or silicone residue remains, exploiting MS100’s tolerance of residual contamination to avoid full substrate stripping.
Curtain walling and rainscreen
Infill-panel and rainscreen perimeter joints on metal, composite and fibre-cement systems needing weatherproofing combined with high movement capacity.
Precast concrete construction
Stack and movement joints between precast panels on industrial, retail and infrastructure buildings, where the 50% MAF allows tighter joint detailing over long runs.
Frequently asked questions
What type of sealant is Fosroc Nitoseal MS100?
Does Nitoseal MS100 need a primer?
How much movement can it accommodate?
Is it really non-staining on marble and stone?
Can it be used for floor or trafficked joints, or in water tanks?
What colours and pack sizes are available?
Can I get Nitoseal MS100 in Delhi NCR and across India?
How we position Fosroc Nitoseal MS100
Within Fosroc’s own range, Nitoseal MS100 is the high-movement, non-staining facade specialist: its 50% MAF sets it apart from its 25% MAF siblings, the general-purpose MS600, the floor/trafficked MS300 and the entry MS60, so MS100 is the right pick wherever premium stone or precast cladding meets significant thermal movement. For horizontal floor and pavement joints, immersed water-retaining structures or heavy engineering joints, the two-part polysulphide and polyurethane systems such as Thioflex 600 (and the airport-grade Thioflex 555) or the Colpor pavement-grade sealants are the more suitable Fosroc choices, often paired with a PVC or hydrophilic waterstop. Against the wider market in India, MS100 competes directly with other MS-polymer and hybrid facade sealants such as Sika Sikaflex (for example Sikaflex-11 FC+ / Sikaflex-AT Facade) and BASF/MBS MasterSeal NP and SL ranges, while STP Limited offers indigenous hybrid and polysulphide alternatives at competitive price points. MS100’s strongest differentiators in that field are its genuine non-staining performance on natural stone, its primerless damp-tolerant application and its high movement class, which together make it a sound specification where finished-facade appearance and longevity are non-negotiable rather than where lowest first cost drives the decision.
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