Fosroc Brushbond
A two-component acrylic polymer-modified cementitious waterproofing membrane that bonds directly to damp concrete and masonry — breathable, non-toxic and trusted on water tanks, basements, roofs and wet areas across India.
What is it?
A two-component, acrylic polymer-modified cementitious waterproofing membrane coating — a Brushbond powder blended with a Nitobond BB acrylic emulsion — that cures to a seamless, flexible, breathable waterproof skin on concrete and masonry.
Where is it used?
Water tanks and reservoirs, swimming pools, basements and retaining walls, RCC roofs and terraces, toilets, bathrooms and balconies, and atmospherically exposed RCC in coastal and aggressive environments.
Why use it?
It needs minimal surface preparation, bonds to damp porous and non-porous surfaces, is non-toxic (suitable for potable water tanks), lets water vapour escape so it will not blister, and forms an effective barrier to carbon dioxide and chloride-ion diffusion that drive rebar corrosion.
How is it applied?
Add clean water to the powder/emulsion mix, stir with a slow-speed drill, then apply by stiff brush, roller or trowel in two coats to a typical 1 mm thickness — the second coat going on as soon as the first is touch-dry; 2 mm with a protective screed is used under hydrostatic or trafficked conditions.
About Fosroc Brushbond
Fosroc Brushbond is one of the longest-serving names in the Indian waterproofing market — a cementitious coating system that distributors and applicators reach for when a project needs a tank, basement or roof made watertight without the cost and rigidity of a fully liquid-applied membrane. Technically it is a two-component, acrylic polymer-modified cementitious waterproofing membrane. The first component is the Brushbond powder, a factory blend of selected cements, graded hard-wearing aggregates and performance additives. The second is Nitobond BB, a liquid component of blended acrylic copolymers. On site you add only clean water, and once mixed in the correct proportions the two parts react to give a tough, flexible coating that keys deep into the substrate. The acrylic polymer is what separates Brushbond from a plain cement slurry: it delivers the adhesion, the elasticity that allows it to bridge static shrinkage cracks, and the durability that lets the coating shrug off weathering and light foot traffic. Because the cured film is breathable, water vapour from inside the structure can still escape, so the coating does not trap moisture or blow off the wall — a recurring failure mode with non-breathable paints and bituminous coats. Fosroc supplies the system in India in two main forms relevant to specifiers: the original Brushbond, an acrylic polymer-modified elastomeric membrane shown to resist positive hydrostatic pressure up to about a 7-metre head, and Brushbond RFX, a higher-performance elastomeric cementitious version paired with Nitobond BBX emulsion and declared compliant with ASTM C836. Both are grey (Brushbond is also offered in white), both are non-toxic and certified-suitable for potable water tanks, and both are designed to reface and even out surface variations while sealing the structure. For contractors, consultants, architects and procurement teams in India, Brushbond occupies a practical middle ground — more robust and crack-accommodating than a basic cementitious slurry, yet simpler and more forgiving to apply than torch-on or fully liquid PU membranes.
The technical insight
The defining characteristic to understand is the polymer-to-cement chemistry. Brushbond is not a paint and not a pure cement slurry — it is a polymer-modified cementitious (PMC) system, where the acrylic emulsion forms a continuous polymer film interlaced through the hydrating cement matrix. This dual structure is why it can do two things a plain cement coat cannot: bond tenaciously to a damp substrate (adhesion to concrete is greater than 1 N/mm²) and accommodate movement, with the standard product rated for static crack accommodation of around 1 mm. Mixed density runs about 1.85–1.95 g/cc for the original Brushbond and 1.68 g/cc for the brushable RFX grade, with a working pot life of roughly 30 minutes at 27°C — short enough that you mix only what can be used quickly and never re-temper with water. The coating is applied damp-on-damp: surfaces should be moistened first, then two coats are laid to reach the recommended 1 mm dry thickness for general waterproofing, building to a minimum 2 mm with a sand-broadcast and protective screed where moderate-to-heavy loads or hydrostatic pressure apply. RFX is the more technically pedigreed grade for exposed RCC protection, carrying ASTM C836 compliance and being tested to ASTM D4060 (abrasion), ASTM D4541 (pull-off adhesion) and ASTM D638 (tensile). Crucially, Brushbond is a coating, not a crack-injection product — its job is to waterproof and protect a sound, repaired substrate, not to plug an active leak.
Where it is used
- Internal and external waterproofing of overhead and underground water tanks and reservoirs (potable-water safe)
- Damp-proofing of basements, retaining walls and below-ground structures against positive water pressure
- Waterproofing of RCC roofs, terraces, chajjas and parapets
- Sealing of toilets, bathrooms, kitchens, balconies and other wet areas before tiling
- Protective anti-carbonation / anti-chloride coating for atmospherically exposed RCC in coastal and industrial zones
- Lining of swimming pools, drainage culverts, sumps and water-retaining civil structures
- Refacing and evening out of honeycombed or imperfect concrete and masonry surfaces
Key advantages
- Bonds directly to damp concrete and masonry, porous or non-porous, with adhesion greater than 1 N/mm²
- Minimal surface preparation and low labour cost compared with torch-on or fully liquid membranes
- Breathable — allows internal water vapour to escape, avoiding blistering and debonding
- Non-toxic and certified-suitable for potable water tanks
- Polymer modification gives flexibility and bridging of static shrinkage cracks (about 1 mm)
- Effective barrier to carbon dioxide, chloride and sulphate ions that drive reinforcement corrosion
- Seamless, jointless finish that withstands weathering, UV and light pedestrian traffic
- RFX grade carries ASTM C836 compliance for specification-grade projects
Limitations & considerations
- It is a coating, not a crack-injection or leak-sealing product — active leaks and moving cracks must be addressed first (e.g. with the Fosroc Nitofill injection range)
- Accommodates only static cracks (around 1 mm); for high-movement joints or dynamic cracking an elastomeric grade such as Brushbond UltraFlex or a PU membrane is more appropriate
- Short pot life of about 30 minutes at 27°C; material cannot be re-tempered with water once it stiffens
- Must not be applied when substrate temperature is below 10°C; hot substrates (over ~40°C) need a primer/slurry coat or dampening
- Requires proper curing and protection from rain, strong wind and traffic during early set
- Exposed-trafficked or hydrostatic-pressure areas need a minimum 2 mm build plus a protective screed
- Shelf life is limited to about 9 months, dropping to under 6 months in high-humidity storage; the Nitobond emulsion must be protected from freezing
Selection & best practice
Treat the substrate, not just the coating, as the waterproofing system. Cut out and repair honeycombing, blowholes and spalled areas with a Fosroc Renderoc repair mortar, and pre-seal any active water ingress with a Renderoc Plug rapid-setting mortar or the Nitofill injection range before Brushbond is applied — Brushbond will protect a sound surface but will not hold back a live leak. Pour the Nitobond emulsion into the mixing drum first, add the powder gradually to the liquid (and the prescribed water) to avoid lumps, and mix with a slow-speed drill for 2–4 minutes; mix only what the crew can use within the 30-minute pot life and never re-temper. Dampen the surface to a saturated-surface-dry condition, then apply two coats with a 100–150 mm stiff brush, putting the second coat on as soon as the first is touch-dry and at right angles to it for full, pinhole-free cover to a 1 mm minimum. For tanks, trafficked roofs or hydrostatic conditions, build to 2 mm, broadcast coarse sand into the wet final coat for mechanical key, and protect with a screed. Cure by keeping the coating moist and shielded from rain, strong wind and traffic during early set, and always confirm coverage against the current Fosroc TDS for the exact grade, since pack sizes and consumption differ between Brushbond and Brushbond RFX.
Specifications
| Product type | Two-component acrylic polymer-modified elastomeric cementitious waterproofing membrane coating |
| Components | Brushbond powder + Nitobond BB acrylic emulsion (RFX grade uses Nitobond BBX); water added on site |
| Colour | Grey (Brushbond also available in white); RFX grey |
| Mixed density | 1.85–1.95 g/cc (Brushbond); approx. 1.68 g/cc (Brushbond RFX, brushable consistency) |
| Pot life | Approx. 30 minutes at 27°C |
| Adhesion to concrete | Greater than 1 N/mm² |
| Static crack accommodation | Approx. 1 mm (RFX) |
| Hydrostatic resistance | Resists positive hydrostatic pressure up to ~7 m head (depends on coating thickness) |
| Application / DFT | Two coats to 1 mm typical; 1–2 mm general; minimum 2 mm with protective screed for heavy load / hydrostatic areas |
| Application method | Stiff brush (100–150 mm), roller or trowel; surfaces should be damp |
| Application temperature | Substrate not below 10°C; prime/dampen hot substrates above ~40°C |
| Standards (RFX) | ASTM C836 compliant; tested to ASTM D4060, ASTM D4541, ASTM D638 |
| Mixing ratio (Brushbond, indl/small) | Powder 23 kg / 6 kg : Nitobond BB 4 L / 1 L : Water 4 L / 1 L |
| Mixing ratio (RFX, indl/small) | Powder 15 kg / 5 kg : Nitobond BBX 4.8 L / 1.63 L : Water 3 L / 1 L |
| Pack sizes | Brushbond: 23 kg powder + 4 L & 1 L emulsion; Brushbond RFX: 15 kg & 5 kg packs |
| Shelf life | 9 months in unopened packs in a dry store (under 6 months in high humidity); protect emulsion from freezing |
| Toxicity | Non-toxic; suitable for potable water tanks (alkaline when wet — use gloves and goggles) |
Industry use cases
Water supply & storage
Internal lining of overhead and underground RCC water tanks and reservoirs where a non-toxic, potable-water-safe waterproof coating is mandatory, applied damp-on-damp to a 1–2 mm build.
Residential & commercial buildings
Waterproofing of toilets, bathrooms, balconies and terraces before tiling, and damp-proofing of basements and lift pits against ground-water pressure.
Infrastructure & civil
Lining of drainage culverts, sumps, swimming pools and water-retaining structures, and seamless protection of RCC roofs on large-footprint buildings.
Coastal & industrial RCC protection
Brushbond RFX applied as an anti-carbonation, anti-chloride barrier coat on atmospherically exposed reinforced concrete in coastal and aggressive industrial environments to slow rebar corrosion.
Repair & rehabilitation
Refacing honeycombed or weathered concrete and masonry after Renderoc mortar repairs, restoring a uniform, durable, waterproof surface on ageing structures.
Frequently asked questions
Is Fosroc Brushbond a real Fosroc product?
What exactly is Brushbond and how does it work?
How much Brushbond do I need and how thick should it be?
Can Brushbond be used inside potable water tanks?
Will Brushbond stop an active leak or seal a moving crack?
What is the difference between Brushbond and Brushbond RFX?
How we position Fosroc Brushbond
Within the Fosroc waterproofing range, the standard Brushbond is the workhorse cementitious membrane for tanks, basements and wet areas, while Brushbond RFX is the specification-grade, ASTM C836-compliant upgrade for protecting exposed RCC. For genuinely flexible, high-movement situations Fosroc itself offers Brushbond UltraFlex (around 150% elongation, ASTM D412) and Brushbond Roofguard (fibre-reinforced, around 100% elongation) — better suited to dynamic cracking than the static-crack-rated base Brushbond. Brushbond is typically paired with Fosroc Renderoc repair mortars for substrate reinstatement and the Nitofill injection range for active leaks, so it rarely works alone. Against the wider Indian market, Brushbond competes with two-component PMC systems such as Sika’s SikaTop Seal / Sika MonoTop range, MBS coatings, Dr. Fixit’s polymer-modified slurries (e.g. Pidicrete URP-based systems and Fastflex), and STP’s products. Brushbond’s strengths are its long track record, potable-water clearance and breathable, easy-brush application; where designers need very high elongation or true dynamic-crack bridging, an elastomeric grade or a liquid-applied PU/acrylic membrane from these alternatives may be the better fit. As an authorised Fosroc distributor and applicator serving Delhi NCR and Pan-India, Space Arc Engineering supplies the correct Brushbond grade and the matching Nitobond emulsion, primer and repair products for the substrate and exposure in question.
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