UltraTech Weather Pro Flex
A flexible, brush-applied cementitious coating that seals wet-area concrete and bridges the fine cracks a rigid render would split alongside.
What is it?
A two-component, polymer-modified cementitious coating – styrene-acrylic liquid mixed with cement-based powder into a brushable, flexible paste.
Where is it used?
Bathrooms, sunken slabs, terraces, balconies, chajjas, water sumps, overhead tanks, swimming pools, and internal wet areas of hotels and hospitals.
Why use it?
It bridges fine shrinkage cracks that plain cementitious waterproofing can’t, while still handling and curing like a cement-based system contractors already know.
How is it applied?
Powder is mixed into liquid at a 2:1 ratio by weight and brushed or rolled on in two coats, with an 8-hour gap between coats and a 2-hour pot life.
About UltraTech Weather Pro Flex
UltraTech Weather Pro Flex is a two-component, polymer-modified cementitious waterproofing coating from UltraTech’s building products range. It pairs a styrene-acrylic liquid polymer with a specially graded cement-based powder, site-mixed in a 2:1 powder-to-liquid ratio by weight into a paste applied with a brush or roller in two coats.
What separates it from an ordinary cement-polymer slurry is elongation. Once cured, the film stretches more than 50 percent at a 1 mm dry film thickness, so it moves with the hairline shrinkage cracking that concrete throws up in its first year rather than splitting alongside it. That flexibility, combined with roughly 0.8 MPa pull-off adhesion to concrete, masonry and plaster, is why it turns up on sunken bathroom slabs, terraces, balconies, chajjas, water sumps, overhead tanks and swimming pool shells across the projects Space Arc supplies in Delhi NCR and pan-India.
It is a positive-side system, built to resist water pushing against the coated face, with a stated resistance up to 7 bar of hydrostatic pressure. On a typical wet-area slab job it is specified together with fillet cove treatment at wall-floor junctions and drain collars, then protected with a screed or tile bed rather than left as the final wearing surface.
The technical insight
The two-hour pot life governs site planning more than any single strength value on the sheet. The acrylic liquid and cement powder begin cross-linking the moment they’re stirred, so crews should mix only what can be laid in that window – batching a full 30 kg pack for a four-hour job wastes material. The 0.65-0.74 sq.m/kg coverage (about 7-8 sq.ft/kg) is for the complete two-coat, 1 mm build; treat the eight-hour recoat gap as a floor, not a target, in humid or shaded conditions.
Also worth flagging: ‘positive side’ waterproofing means the coating relies on water pressing it into the substrate. Specify it on the wrong face – inside a retaining wall pushed by water from outside, say – and it can be forced off under load however well it was applied.
Where it is used
- Sunken bathroom and kitchen slabs before screeding
- Terraces, balconies and chajjas exposed to weathering
- Water sumps and underground/overhead water tanks
- Swimming pool shells and water-retaining RCC structures
- Internal wet areas of hotels, hospitals and IT parks
- Sloping roofs and domes on positive-side application
- Repair and re-waterproofing of old, sound concrete surfaces
Key advantages
- Elongates over 50% at 1 mm DFT, bridging fine shrinkage cracks a rigid coating would split along
- Roughly 0.8 MPa pull-off adhesion (ASTM D 4541) to concrete, masonry and plaster
- Rated for positive-side hydrostatic pressure up to 7 bar, suiting tanks, sumps and pools
- Simple two-coat brush or roller application – no specialist spray or torch equipment
- Supplied in 3 kg, 15 kg and 30 kg packs, sized for patch repairs and full-slab jobs
Limitations & considerations
- Two-hour pot life demands disciplined batching – mixed material can’t be held over or reused later
- A positive-side coating only, not designed for negative-side or below-grade tanking work
- Bridges fine shrinkage cracks, not active structural cracks or moving expansion joints
- Needs an 8-hour gap between coats and 3-5 days’ final cure before water contact – schedules must allow for it
Selection & best practice
Prepare the substrate to sound, contamination-free concrete or masonry – remove laitance, oil and loose material, and dampen (not flood) the surface before application. Treat wall-to-floor junctions, pipe penetrations and drain outlets with a fillet cove and, where movement is expected, a reinforcing mesh strip before the field coats go on. Apply the two coats in alternating directions to close pinholes and even out film thickness, respecting the eight-hour minimum recoat gap. Keep the finished membrane protected from foot traffic and rain through its 3-5 day final cure, and lay a protective screed or tile bed over it rather than leaving it exposed.
Specifications
| Product type | Two-component, polymer-modified cementitious waterproofing coating |
| Composition | Styrene-acrylic liquid polymer + specially graded cementitious powder |
| Mixing ratio | 2 parts powder : 1 part liquid, by weight |
| Elongation | >50% at 1 mm DFT |
| Tensile strength | ~1.2 MPa |
| Pull-off adhesion | ~0.8 MPa (ASTM D 4541) |
| Hydrostatic resistance | Up to 7 bar, positive side |
| Coverage | 0.65-0.74 sq.m/kg (~7-8 sq.ft/kg) for 2 coats @ 1 mm DFT |
| Number of coats | 2 coats, brush or roller applied |
| Recoat interval | Minimum 8 hours between coats |
| Pot life | ~2 hours after mixing |
| Final cure | 3-5 days before water contact/service |
| Pack sizes | 3 kg, 15 kg, 30 kg |
| Substrates | Concrete, masonry, plaster (new and sound old surfaces) |
Industry use cases
Residential
Sunken bathroom and kitchen slabs, balconies and chajjas before tiling or screeding.
Hospitality & healthcare
Internal wet areas and kitchens in hotels and hospitals where downtime for re-work is costly.
Water retaining structures
Water sumps, overhead tanks and pool shells, using the coating’s positive-side hydrostatic rating.
Terraces & roofs
Exposed terraces and sloping roofs needing a flexible coating ahead of tiling or a protective screed.
Frequently asked questions
Does UltraTech Weather Pro Flex need a primer before application?
Can it be left as the final, exposed surface on a terrace?
What’s the difference between Weather Pro Flex and Hi-Flex?
How soon can a treated water tank or sump be filled?
Can it be used on the outside of a basement wall, below ground?
How we position UltraTech Weather Pro Flex
Within Space Arc’s UltraTech range, Weather Pro Flex is the standard flexible cementitious coating – specified ahead of Weather Pro Hi-Flex when the substrate isn’t expected to move much beyond ordinary shrinkage, and usually the more economical choice for routine bathroom, terrace and tank work. Where a BOQ names a Fosroc equivalent instead, Brushbond RFX occupies the same slot, and the choice often comes down to brand preference or project approvals rather than a real performance gap.
Fosroc Brushbond RFX — A specifier already standardised on Fosroc, or working to a BOQ that names it, would reach for Brushbond RFX – a comparable two-component acrylic-modified cementitious coating for the same wet-area and tanking scope.
Related Waterproofing products
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