Fosroc Nitoseal PU40 N
Single-component, low-modulus gun-grade polyurethane sealant for building and expansion joints — 25% movement accommodation, primerless on most substrates, ISO 11600 Type F 25LM.
What is it?
A one-part, low-modulus, gun-grade (non-sag) elastomeric joint sealant based on moisture-curing polyurethane technology, designated by Fosroc India as Nitoseal PU40 IN.
Where is it used?
Vertical and slightly inclined movement and construction joints in concrete, brickwork, blockwork, precast panels and stone cladding, plus perimeter sealing around doors and windows and non-trafficked floor joints.
Why use it?
Accommodates 25% joint movement without cracking or losing adhesion, cures fast from a single cartridge with no on-site mixing, bonds to most building substrates primerless, and resists UV and weathering — ideal for facades and superstructures.
How is it applied?
Gun-applied from 600 ml sachets via the Fosroc GX gun into a clean, dry joint over a backer rod or bond breaker, then tooled off to a 2:1 width-to-depth profile; primerless on most substrates, with Fosroc Primer 4 / Primer 7 only for high-movement or immersed joints.
About Fosroc Nitoseal PU40 N
Fosroc Nitoseal PU40 N is the non-sag, gun-grade member of the Nitoseal PU40 family — a single-component sealant built on moisture-curing polyurethane chemistry and supplied across India by Fosroc Chemicals (India) Pvt. Ltd. In the Indian catalogue it appears as Nitoseal PU40 IN, and the “N” designation flags the non-slumping paste form intended for vertical and overhead joints, as distinct from any self-levelling pouring variants used for horizontal floor work. Out of the cartridge it is a smooth, non-slumping paste that is gunned straight into the joint, tooled to profile, and then left to skin and cure on contact with atmospheric moisture. Because it is a one-part product, there is no base-and-activator mixing, no pot-life clock, and no batch-to-batch ratio error on site — a practical advantage on Indian projects where joint sealing is often done by labour crews under time pressure on scaffolding or at height. It is a low-modulus formulation, meaning it stays soft and stretchy and transfers only low stress back into the joint arrises as the structure moves, which is exactly what facade panels, masonry and lightweight cladding need. Fosroc classifies it as ISO 11600:2002 Type F (facade) Class 25 Low Modulus, with parallel compliance to ASTM C920 Type S Grade NS Class 25 and US Federal Specification TT-S-00230a Type II Grade NS Class 25. The product is positioned by Fosroc for sealing joints in concrete, brickwork, blockwork, precast panels and stone cladding, for perimeter sealing around door and window frames, and for non-trafficked floor joints — a broad general-purpose building and expansion-joint sealant rather than a specialist trafficked or pavement product. For Space Arc’s customers across Delhi NCR and Pan-India, it is the everyday workhorse PU sealant: a step up in movement capability and durability from acrylic and many silicone gap-fillers, and a more convenient single-component alternative to two-part polysulphides like Fosroc Thioflex 600 where the heavy-duty performance of a polysulphide is not strictly required.
The technical insight
The engineering value of Nitoseal PU40 N sits in three linked properties: low modulus, a 25% movement accommodation factor (MAF), and moisture-cure polyurethane chemistry. Low modulus (Shore A hardness around 25) means the cured sealant develops low internal stress at a given strain, so it pulls less hard on the joint edges — critical on weaker substrates such as render, lightweight block or thin stone, where a high-modulus sealant could peel the arris or fail cohesively. The 25% MAF defines the design envelope: the joint can open and close by up to a quarter of its installed width over its life and the sealant should still bridge it. That single number drives joint design — for a structure that will move, say, 6 mm, the designer needs a joint of at least roughly 24 mm so 6 mm is within 25% of width. Movement is referenced to the as-installed width, which is why sealing at the right time of day and temperature matters. The third property, moisture cure, explains the behaviour on site: skinning in about 2 hours and a cure rate near 3 mm per 24 hours at 20°C / 50% RH — fast in humid conditions but slower in dry winter air, so deep joints take days, not hours, to cure fully through. Two-part PU and polysulphide systems cure chemically throughout the section and are less depth- and humidity-dependent, which is the trade-off against the one-part convenience of PU40 N. Adhesion is the other technical lever: PU40 N is primerless on most clean, sound substrates, but Fosroc specifies Primer 7 on porous surfaces and Primer 4 on non-porous surfaces wherever the joint sees high movement or intermittent immersion, because PU bonds are vulnerable to hydrolysis at the interface under standing water.
Where it is used
- Vertical and inclined movement (expansion) joints in concrete superstructures, facades and parapets
- Construction and contraction joints in cast in-situ concrete, blockwork and brickwork (over a bond breaker)
- Perimeter sealing of door and window frames against concrete, masonry or stone reveals
- Joints between precast concrete panels and around precast cladding units
- Stone and natural-stone cladding joints on elevations
- Connection and movement joints in blockwork and brickwork in commercial and residential buildings
- Non-trafficked floor joints in plant rooms, terraces and similar areas not exposed to vehicular traffic
- Weather sealing of joints in basements, subways and similar civil structures (with priming where intermittently immersed)
Key advantages
- Single component — gunned straight from the sachet with no mixing, no pot life and no on-site mix-ratio error
- Low modulus with 25% movement accommodation factor, so it absorbs joint movement without cracking or de-bonding while imposing low stress on joint edges
- Primerless adhesion to most common building substrates, speeding up application
- Fast moisture cure — skins in roughly 2 hours, allowing early protection against weather and contamination
- Good UV and weathering resistance, suited to exposed facades and parapets in Indian sun
- ISO 11600 Type F 25LM, ASTM C920 and US Fed Spec compliant — easy to specify against international standards
- Smooth, non-slumping paste that holds shape in vertical and overhead joints and tools cleanly
- Wide service temperature range of -40°C to +70°C, covering Indian climatic extremes from hill stations to peak summer surfaces
- Available in a range of colours to suit architectural finishes (current range from Fosroc)
Limitations & considerations
- Not recommended for unprimed joints subject to continuous water immersion — these require priming and, for permanently wet conditions, a different chemistry
- Not suitable for horizontal floor or deck joints where vehicular traffic or mechanical abuse is encountered (use a trafficable system such as a pouring-grade or polysulphide sealant)
- Joint widths are limited to 5–35 mm; widths above 35 mm need Fosroc Technical Service advice
- Must not be applied to frost-bearing surfaces, or where the temperature will stay below freezing for more than 24 hours
- Cure is depth- and humidity-dependent (about 3 mm per 24 hours), so deep joints and dry winter conditions extend full-cure time
- Cannot be applied over joints contaminated with grease, wax, corrosion, bitumen or cement laitance without thorough cleaning
- Special architectural finishes (e.g. certain natural stones prone to staining) require adhesion and compatibility testing before acceptance
- Contains a small amount of isocyanate and low-flash-point solvent, so standard PPE and ventilation precautions apply
Selection & best practice
Design moving joints to an optimum width-to-depth ratio of 2:1, with an overriding minimum sealant depth of 5 mm on non-porous substrates and 10 mm on porous substrates, and keep the joint width inside the 5–35 mm working range (consult Fosroc above 35 mm). Always control sealant depth with a closed-cell backer rod (such as Fosroc Hydrocell XL, Backing Rod or Expandafoam) sized about 25% larger than the joint width; in construction or contraction joints with no cellular filler, use a bond-breaker tape so the sealant bonds on two faces only and is free to stretch. Prepare joint faces to be clean, dry and frost-free — remove dirt, laitance, loose material, rust, scale and old sealant back to sound concrete or clean substrate. Rely on the primerless capability for most general joints, but apply Fosroc Primer 7 (porous) or Primer 4 (non-porous) on high-movement or intermittently immersed joints, brushing thinly to avoid puddling, and re-prime if a primed porous joint is left open beyond 4 hours. Gun the sealant in firmly to avoid air entrapment, tool off promptly to a slightly concave profile for full edge contact, and mask arrises for a neat line where finish matters. Apply only between 5°C and 50°C, and where possible seal at a moderate, stable temperature so the joint is near mid-position rather than fully open or closed. Always confirm adhesion on the actual project substrate before bulk application.
Specifications
| Product type / chemistry | Single-component, low-modulus polyurethane (PU), moisture-curing elastomeric sealant |
| Grade / form | Gun grade, non-sag (smooth, non-slumping paste) |
| Movement Accommodation Factor (MAF) | 25% |
| Standards compliance | ISO 11600:2002 Type F 25LM; ASTM C920-95 Type S, Grade NS, Class 25; US Fed Spec TT-S-00230a Type II, Grade NS, Class 25 |
| Joint width range | 5 mm to 35 mm (above 35 mm consult Fosroc Technical Service) |
| Width-to-depth ratio | 2:1 optimum; min depth 5 mm (non-porous) / 10 mm (porous) |
| Hardness at 20°C | Shore A approx. 25 (low modulus) |
| Skinning time | Approx. 2 hours at 20°C / 50% RH |
| Cure rate | Approx. 3 mm per 24 hours at 20°C / 50% RH |
| Primer requirement | Primerless on most substrates; Primer 7 (porous) / Primer 4 (non-porous) for high-movement or intermittently immersed joints |
| Application temperature | 5°C to 50°C |
| Service temperature range | -40°C to +70°C |
| UV resistance | Very good |
| Colours | Range of colours (current range from Fosroc) |
| Pack size | 600 ml sachets (applied with Fosroc GX gun) |
| Shelf life | 12 months in original unopened sachets, stored cool, dry and out of direct sunlight |
Industry use cases
Commercial & high-rise facades
Sealing movement and panel joints between precast concrete, masonry infill and stone cladding on elevations and parapets, where low modulus and 25% MAF keep the seal intact as the facade expands and contracts in Delhi NCR’s wide seasonal temperature swing.
Residential & institutional buildings
Perimeter sealing of door and window frames and brick/block movement joints, giving a fast single-component weather seal that resists UV and rain ingress without specialist mixing equipment.
Precast concrete construction
Weather and movement sealing of joints between precast wall panels and cladding units in factory-built and modular projects, using a non-sag paste that holds line in vertical joints.
Civil & infrastructure structures
Sealing weather and movement joints in basements, subways and similar concrete structures, with Primer 4/7 applied where joints are intermittently immersed.
Industrial buildings & plant rooms
Non-trafficked floor and wall joints in plant rooms, terraces and service areas where the joint sees movement and weather but no vehicle traffic, as an economical alternative to two-part systems.
Frequently asked questions
Is Fosroc Nitoseal PU40 N a polyurethane or polysulphide sealant?
Does Nitoseal PU40 N need a primer?
How much movement can the joint take?
What joint widths and depths does it suit?
Can it be used on floors or trafficked areas?
How long does it take to skin and cure?
How we position Fosroc Nitoseal PU40 N
Within the Fosroc sealant range, Nitoseal PU40 N is the convenient, single-component, low-modulus PU workhorse for general building and expansion joints on facades, masonry, precast and around openings. Step up to a two-part polysulphide such as Fosroc Thioflex 600 (gun and pouring grades) where you need heavier-duty performance, trafficked floor joints, or fuel/chemical exposure, and to Fosroc Colpor 200PF — a cold-applied pouring-grade sealant — for pavement, road, runway and hardstanding joints subject to traffic, fuel and oil spillage. For self-levelling horizontal floor joints, Fosroc’s pouring-grade Nitoseal/PU280-type products are the right call rather than the non-sag PU40 N. Against the wider market, PU40 N competes directly with Sika Sikaflex (e.g. Sikaflex-PRO and Sikaflex-11 FC for general building and facade joints), BASF/MBCC MasterSeal (MasterSeal NP/SL polyurethane grades) and STP/Choksey polyurethane and polysulphide sealants widely used on Indian projects. The choice usually comes down to required movement class, whether the joint is trafficked or immersed, single- versus two-part convenience, and approved-vendor lists on the project. As an authorised Fosroc distributor and applicator covering Delhi NCR and Pan-India, Space Arc Engineering supplies Nitoseal PU40 N alongside the matching Fosroc primers, backer rods and application equipment, and can advise on joint design, MAF, primer selection and the right grade for trafficked or immersed conditions.
Related Sealants & Joint Treatment products
Source Fosroc Nitoseal PU40 N for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.