UltraTech Weather Pro Hi-Flex
A two-component elastomeric coating engineered for India’s punishing roof and wall exposure, brush-applied and rated to 5 bar positive-side pressure.
What is it?
A two-component, cement-based, styrene-acrylic elastomeric waterproof coating, supplied as a grey powder plus liquid polymer that’s mixed on site.
Where is it used?
Exposed roof slabs, terraces, balconies, domes, external walls, sunken slabs, bathrooms and swimming pools, on the positive (water-facing) side.
Why use it?
Elongation beyond 100% lets the cured film stretch and bridge hairline movement cracks instead of cracking with them, while holding back water to 5 bar.
How is it applied?
Powder is stirred into the liquid at a fixed 1.4:1 ratio and brushed on in two coats, each roughly perpendicular to the last, inside a 2-hour pot life.
About UltraTech Weather Pro Hi-Flex
UltraTech Weather Pro Hi-Flex is the higher-elongation member of UltraTech’s Weather Pro range, built for surfaces that genuinely move — exposed RCC roofs, parapets, domes and sun-facing walls that expand through a Delhi NCR summer and contract once the monsoon cools them. It ships as two components: a grey cementitious powder carrying styrene-acrylic polymer and fillers, and a liquid polymer, combined on site at a fixed 1.4 parts powder to 1 part liquid ratio. Brushed on in two coats, roughly perpendicular to each other, it cures into a continuous elastomeric skin that stretches past 100% elongation without losing its water seal — the property that separates it from an ordinary cementitious coating, which stays rigid and cracks wherever the substrate does. The cured film also breathes, letting vapour escape from the slab while keeping liquid water out, which matters on occupied terraces that soak every monsoon and need to dry out afterward.
The technical insight
The chemistry is fairly direct. The powder component is a modified Portland cement blended with fine fillers; the liquid is a styrene-acrylic polymer emulsion at roughly 50% solids. Brushed together at around 1 mm combined dry film thickness across two coats, the acrylic phase forms a continuous flexible matrix around the cement particles, so the cured film behaves more like a rubberised skin than a mineral render. That’s what lets it stretch beyond 100% elongation under a 50 kg/sq.cm tensile pull, tested to ASTM D 412, while holding a pull-out bond strength above 0.3 N/mm² to concrete under ASTM D 4541 — enough to resist delamination as the substrate expands and contracts through the day, without a separate primer coat. Water resistance is rated to 5 bar positive-side pressure under DIN 1048, which is why UltraTech pitches it for pool shells and sump tanks as much as roofs. The 2-hour pot life is short by design; batches mixed ahead of that window lose workability before they’re brushed out.
Where it is used
- Exposed RCC roof slabs and terraces, ahead of a screed or tiling
- Domes, sloped roofs and curved surfaces, topped with UltraTech Super Stucco under 6 mm
- External walls and high-rise facade bands exposed to thermal cycling
- Balconies, sunken slabs, bathrooms and kitchens, positive side only
- Swimming pool shells, sump tanks and water-retaining structures
- Old and new concrete of any geometry, positive-side waterproofing only
Key advantages
- Elongation beyond 100% lets the membrane bridge hairline and thermal cracks instead of splitting with them
- 5 bar positive-side water resistance, verified to DIN 1048
- Breathable film — vapour escapes while liquid water is kept out, cutting blistering risk
- Self-curing and brush-applied, with no membrane sheets, torches or spray rigs to hire
- Negligible wastage, since only the quantity needed for the 2-hour pot life gets mixed
- Resists occasional foot traffic once cured, useful on accessible terraces
Limitations & considerations
- Positive-side use only — not rated for negative-side or below-grade hydrostatic pressure
- Two-hour pot life demands disciplined batching on larger roof pours
- Needs a sound, saturated-surface-dry substrate; won’t bridge active leaks or structural cracks on its own
- Exposed roofs need a protective screed such as Floorkrete or Super Stucco for long-term durability
Selection & best practice
Treat surface preparation as half the job. Grind or wire-brush the slab back to sound concrete and jet-wash off dust and laitance, fill non-structural cracks, and pressure-grout honeycombed patches with UltraTech Mykrofill before starting. Pre-wet the substrate to a saturated-surface-dry condition — a thirsty slab pulls water out of the mix and starves the film. Mix only what can be brushed out inside the 2-hour pot life, apply each 0.5-0.6 mm coat with a stiff nylon brush, and hold a minimum 8-hour gap before the second, perpendicular coat. On exposed roofs, always run a sandwich system with a protective screed over the cured membrane rather than leaving it exposed long-term.
Specifications
| Chemistry / Type | Two-component, cement-based, styrene-acrylic polymer elastomeric coating |
| Mix Ratio | 1.4 parts powder : 1 part liquid, by weight |
| Elongation | >100% at a tensile pull of 50 kg/sq.cm, @ 1 mm DFT (ASTM D 412) |
| Pull-out Adhesion | >0.3 N/mm² to concrete (ASTM D 4541) |
| Water Resistance | Up to 5 bar positive-side pressure (DIN 1048) |
| Pot Life | 2 hours |
| Coat Thickness | 0.5-0.6 mm DFT per coat, applied in 2 coats |
| Coverage | 5-6 sq.ft (approx. 0.46-0.56 sq.m) per kg of combined mixed product @ 1 mm DFT in 2 coats |
| Application Method | Brush; 2 coats applied perpendicular to each other, min. 8-hour gap between coats |
| Finish / Colour | Smooth, breathable grey coating |
| Shelf Life | 12 months from date of manufacture, stored cool and dry |
| Pack Sizes | 12 kg and 24 kg |
Industry use cases
Residential terraces & roofs
Applied under a Floorkrete or tile screed on exposed RCC roofs to stop monsoon ingress while tolerating daily thermal movement.
High-rise facades
Used on parapets and wall bands where thermal cycling would crack a rigid cementitious coating.
Water-retaining structures
Applied inside sump tanks and pool shells for its 5 bar rating and non-toxic, chemical-resistant film.
Domes & sloped roofs
Specified with a Super Stucco topping under 6 mm, where a standard screed can’t be laid.
Frequently asked questions
What’s the difference between Weather Pro Flex and Weather Pro Hi-Flex?
Can it be used below grade or on the negative side of a wall?
How much does one 12 kg pack cover?
How soon can the area be tested for leaks after application?
How we position UltraTech Weather Pro Hi-Flex
Within Space Arc’s UltraTech range, Weather Pro Hi-Flex sits above Weather Pro Flex as the coating to specify wherever elongation matters more than raw film build — exposed roofs, domes and facades with real thermal cycling, rather than static below-grade work suited to a rigid or crystalline system. Against fully bonded sheet membranes, it’s the faster, contractor-friendly route: no torching, no lapped joints, just brush, cure and screed — which is why it shows up so often on occupied residential roofs across Delhi NCR.
Fosroc Brushbond UltraFlex — Specifiers already standardised on Fosroc systems, or projects wanting elongation beyond 150% with an international elastomeric membrane pedigree, may prefer Brushbond UltraFlex, though it typically costs more per kg than Weather Pro Hi-Flex.
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