STP ShaliPrime AC WB
Water-based emulsified resin primer that anchors acrylic and other liquid-applied waterproofing membranes to concrete and masonry, with a fast 1 to 3 hour recoat window and low-odour, water-cleanup application.
What is it?
A milky-white, single-component emulsified resin primer with 43% solids that seals concrete and masonry pores and creates the adhesion bridge for water-based liquid waterproofing membranes.
Where is it used?
Terrace and roof slabs, exterior and interior concrete, plastered masonry, parapets and plinths, wherever an acrylic membrane, another liquid-applied system or even decorative paint follows.
Why use it?
It penetrates porous substrates deeply, binds surface dust, and is moisture insensitive, so it works on the slightly damp slabs that Indian terrace jobs actually present after cleaning.
How is it applied?
Stir well and apply by brush, roller or spray at about 100 g/m² per coat; give porous substrates two coats and overcoat with the membrane once the film is tack free, typically in 1 to 3 hours.
About STP ShaliPrime AC WB
ShaliPrime AC WB is STP Limited’s water-based primer for the acrylic and liquid-applied waterproofing family. It is an emulsified resin dispersion, milky white in the bucket and drying to a thin matt white film, formulated to prepare concrete and masonry before a water-based liquid membrane goes on. On a cleaned slab it soaks into open capillaries, consolidates the dusty top layer and evens out suction, so the membrane that follows wets the surface uniformly instead of losing water into a thirsty substrate.
For contractors the practical appeal is speed and site friendliness. The primer is touch dry in 30 to 60 minutes at 30°C and ready for the next coat in 1 to 3 hours, which keeps a prime-plus-membrane sequence within a single working day. Because it is water based there is no solvent odour, making it suitable for occupied residential societies, schools and hospitals, and tools clean up with plain water. Space Arc supplies genuine STP material in 20 kg buckets across Delhi NCR and Pan-India.
The technical insight
The mechanism is film formation by coalescence. Fine resin particles are carried in water at 43 ± 1% solids; the low-viscosity emulsion wicks into capillary pores far more readily than a full-bodied coating would. As the water evaporates and partly absorbs into the substrate, the particles pack together and fuse into a continuous film of roughly 25 microns dry thickness that is mechanically keyed into the concrete. This film does two jobs at once: it locks down laitance and fine dust that would otherwise become a weak boundary layer under the membrane, and it throttles substrate suction so the acrylic topcoat can coalesce properly instead of drying too fast and pinholing. Because curing needs water to leave rather than solvent, the primer tolerates residual dampness in the slab, though the same physics means drying slows in cool, humid weather.
Where it is used
- Priming terrace and roof slabs before acrylic elastomeric waterproofing membranes
- Exterior and interior concrete surfaces ahead of any liquid-applied membrane
- Masonry and plastered walls before water-based waterproof coatings
- Parapets, chhajjas and plinth bands prior to elastomeric treatment
- Balconies, podium slabs and utility areas receiving brush-applied liquid systems
- Primer coat under decorative paints on concrete and masonry
- Consolidating porous, dusty slabs during pre-monsoon terrace refurbishment
Key advantages
- Highly penetrative, binding surface dust and laitance for stronger membrane adhesion
- Adds adhesion plus flexibility at the primer line, supporting elastomeric movement above
- Moisture insensitive, so it accepts slightly damp (not wet) concrete after cleaning
- Water based and low odour, safe for occupied buildings and enclosed areas
- Fast turnaround with 30 to 60 minute touch dry and a 1 to 3 hour recoat window
- Single component, applied by brush, roller or spray with plain-water tool cleanup
- Economical at roughly 100 g/m² per coat, about 200 m² theoretical from one 20 kg bucket
Limitations & considerations
- Not for bituminous or solvent-based systems; STP ShaliTex Primer is the correct primer there
- Application window is 10°C to 40°C, and rain before the film dries will wash out fresh primer
- Standing water must be removed first, even though damp substrates are acceptable
- Porous substrates need two coats, so practical consumption can exceed the theoretical figure
- It is only an adhesion layer, never a waterproofing coat on its own, and must be overcoated
- Shelf life is 6 months unopened, shorter than many primers, so order against near-term use
Selection & best practice
Surface preparation decides how well any primer performs. Remove loose gravel, dirt, oil, grease and foreign matter, blow the slab down with dry air, and grind high spots or friable patches smooth before starting. Roll the bucket three to four times and stir the material thoroughly, because emulsions settle in storage. Apply by brush, roller or airless spray at about 100 g/m² per coat, working it into the surface rather than flooding it; on porous or absorbent substrates apply a second coat once the first will take it. The critical timing rule: apply the waterproofing membrane only after the primer is fully tack free, normally within 1 to 3 hours at 30°C, and allow longer in humid or cool conditions. Wear gloves and eye protection, and keep the area ventilated.
Specifications
| Form and finish | Milky white liquid; dries to a white matt film |
| Solids content | 43 ± 1.0% |
| Density at 25°C | 1.30 ± 0.03 g/cc |
| Theoretical coverage | 100 g/m² per coat (surface-condition dependent) |
| Dry film thickness | 25 microns per coat |
| Touch dry (30°C, 60% RH) | 30 to 60 minutes |
| Recoat time | 1 to 3 hours |
| Hard dry | 12 to 24 hours |
| Application temperature | 10°C to 40°C |
Industry use cases
Residential Societies
Pre-monsoon terrace waterproofing in occupied towers, where the low-odour, water-based chemistry avoids complaints and the fast recoat keeps scaffold time short.
Commercial & Institutional
Roofs of offices, schools and hospitals ahead of acrylic elastomeric systems, where low-VOC materials are increasingly a specification requirement.
Real Estate Developers
New towers and podiums where terraces receive liquid-applied membranes before handover, with priming and first membrane coat achievable in one shift.
Waterproofing Applicators
Contract teams standardising on one primer for concrete, plaster and masonry across acrylic and other water-based liquid membrane jobs.
Industrial Facilities
Concrete roofs of plants and warehouses being upgraded with elastomeric coatings, where damp-tolerant priming shortens weather-dependent schedules.
Frequently asked questions
Can ShaliPrime AC WB be used under bituminous coatings or APP membranes?
Can it be applied on damp concrete?
How soon can the waterproofing membrane go on?
How much primer does a 1,000 sq ft terrace need?
Is ShaliPrime AC WB a waterproofing coat by itself?
What pack size and shelf life should I plan around?
How we position STP ShaliPrime AC WB
Within the STP range, ShaliPrime AC WB is the standard first coat under ShaliCryl acrylic elastomeric membranes and other Shali water-based liquid systems; where the topcoat is bituminous, switch to STP ShaliTex Primer. As authorised distributors for multiple brands, Space Arc can also supply Fosroc Nitoproof WB Primer when a project is specified around Fosroc liquid membranes, or Dr. Fixit terrace systems where the consultant has standardised on that family, so the primer always matches the membrane manufacturer’s warranty conditions.
Fosroc Nitoproof WB Primer — Specifiers running a Fosroc Nitoproof liquid-membrane system typically choose Nitoproof WB Primer so the primer and membrane sit within a single manufacturer’s system warranty.
Related Waterproofing products
Source STP ShaliPrime AC WB for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.