STP ShaliPrime WP SB
A solvent-borne coal-tar primer that grips damp concrete, seals porosity and locks liquid waterproofing membranes to the deck, with built-in root resistance for terrace gardens.
What is it?
A black, solvent-based anti-root primer built on coal-tar pitch and polyamide resin, formulated to prepare surfaces before liquid-applied waterproofing membranes.
Where is it used?
Concrete terraces, podium slabs, basements, metal and asbestos roofs, and terrace-garden decks where a membrane will follow.
Why use it?
It penetrates and tacks up even on slightly damp or porous substrates, giving the membrane a clean, bonded base and resisting root ingress on green roofs.
How is it applied?
Stir, then apply a single thin coat by brush, roller or spray at roughly 5-7 sq.m per litre; overcoat with the membrane once the primer is tack-free (about 20 minutes).
About STP ShaliPrime WP SB
STP ShaliPrime WP SB sits at the very first step of a liquid-membrane waterproofing system, and it is the step most site teams underestimate. Before any APP membrane, PU coating or acrylic topping goes down, the deck has to be sealed and made receptive; a raw concrete slab is dusty, porous and chemically indifferent to whatever is laid over it. ShaliPrime WP SB is the coat that changes that. It is a solvent-borne primer whose thin, low-viscosity film soaks into the surface, binds loose fines, and leaves behind a tacky, membrane-friendly skin that the subsequent coat can key into.
What sets this grade apart from an ordinary bituminous primer is the anti-root character carried in its coal-tar pitch and polyamide-resin chemistry. On terrace gardens, planter boxes and landscaped podiums, root penetration is a slow but relentless threat to any waterproofing layer. By priming with an anti-root grade, the specifier builds root resistance into the substrate itself rather than relying on the membrane alone. Because it is solvent-based, it also stays workable on substrates that are cool, shaded or not bone-dry, which is precisely where a water-based primer tends to struggle. For Space Arc’s contractor and consultant clients across Delhi NCR and Pan-India, it is a dependable, no-drama primer for the jobs where the membrane simply must hold.
The technical insight
The primer works on two fronts at once, and both come from its formulation. The coal-tar pitch and xylene carrier keep the viscosity low (around 40 seconds, B4 cup) so the liquid wicks into surface pores instead of sitting on top. As the xylene flashes off, the pitch and polyamide resin are left behind as an 8-10 micron film that is chemically compatible with bituminous and pitch-modified membranes laid over it. That thin film is the bond bridge: it dries tack-free in about 20 minutes yet stays adhesive enough for the membrane to fuse into, which is why it grips where a glossy sealed slab would delaminate. The polyamide component adds flexibility and helps span hairline shrinkage cracks, while the coal-tar backbone brings the root-resistance and moisture tolerance that let it be applied on damp, shaded decks without whitening or lifting.
Where it is used
- Priming RCC terrace and roof slabs before APP/SBS torch-applied membranes
- Base coat under liquid-applied PU and bituminous waterproofing membranes
- Anti-root priming for terrace gardens, planters and landscaped podium decks
- Sealing porous or slightly damp basement and retaining-wall concrete
- Priming metal roof sheets and asbestos sheets ahead of membrane application
- Preparing sunken slabs, chajjas and parapet junctions before waterproofing
- Priming timber and wooden substrates that will receive a membrane
- Binding surface dust and laitance on green, freshly cured concrete decks
Key advantages
- Highly penetrative, low-viscosity film that anchors into porous concrete
- Built-in root resistance for terrace-garden and podium waterproofing
- Tolerates damp and shaded substrates where water-based primers struggle
- Fast surface dry, tack-free in about 20 minutes for quicker overcoating
- Helps bridge hairline shrinkage cracks thanks to its flexible resin base
- Multi-substrate: bonds on concrete, metal, asbestos and wood
- Brush, roller or spray application with no special site equipment
- Chemically matched to bituminous and pitch-modified membranes
Limitations & considerations
- Solvent-based and flammable (flash point above 23 degrees C); keep away from ignition sources and provide ventilation
- Contains xylene and coal-tar pitch, so it carries a strong odour and needs PPE and cross-ventilation in enclosed areas
- A primer only, not a standalone waterproofing layer; it must be overcoated with a membrane
- Not intended for potable-water tanks or food-contact surfaces
- Should not be applied over standing water, oily or contaminated surfaces
- Solvent carrier means it is less eco-friendly than the water-based ShaliPrime WP WB where low-VOC is a requirement
Selection & best practice
Start with a sound, clean deck: remove loose gravel, dirt, oil and grease with a jet of dry air, and mechanically grind or wire-brush the surface smooth before priming. Stir the primer with a slow-speed paddle to a homogeneous mix and let it stand briefly so entrapped air escapes. Apply one thin, even coat by brush, roller or spray at roughly 5-7 sq.m per litre, taking special care to wet parapet junctions, drains and corners. Do not flood the surface; a thin, well-worked coat penetrates better than a thick puddled one. Once the film is tack-free (around 20 minutes at 30 degrees C), lay the waterproofing membrane while the primer is still fresh so the two bond as one system. Work with adequate ventilation, keep the pack sealed and away from heat and open flame, and wear gloves and eye protection throughout.
Specifications
| Product Type | Solvent-based anti-root primer for waterproofing membranes |
| Base Chemistry | Coal-tar pitch with polyamide resin, xylene carrier |
| Appearance | Black liquid, characteristic odour |
| Density at 25 degrees C | 1.00 plus/minus 0.02 gm/cc |
| Viscosity (B4 Cup, 25 degrees C) | 40 plus/minus 5 sec |
| Theoretical Coverage | 5-7 sq.m per litre (surface dependent) |
| Surface Drying Time (30 degrees C, 55% RH) | Max 20 minutes |
| Dry Film Thickness | 8-10 micron |
| Flash Point (Abel’s Closed Cup) | Above 23 degrees C |
| Pack Size / Shelf Life | 20 L pack; 12 months unopened |
Industry use cases
Terrace Gardens & Podiums
Anti-root priming under liquid membranes on landscaped decks, planters and green roofs, adding a root barrier at the substrate level.
Residential & Commercial Roofing
Priming RCC terraces and slabs before APP/SBS or PU membranes on apartments, offices and institutional buildings.
Basements & Below-Grade
Sealing porous, slightly damp basement and retaining-wall concrete ahead of a waterproofing membrane.
Industrial & Metal Roofs
Priming metal and asbestos roof sheets in factories and warehouses to key liquid membranes to otherwise slick surfaces.
Repair & Refurbishment
Re-priming aged decks during waterproofing overhauls where a fast-drying, damp-tolerant primer keeps the programme moving.
Frequently asked questions
What is the coverage of ShaliPrime WP SB?
How is it different from ShaliPrime WP WB?
Can I apply it on a slightly damp surface?
How long before I can lay the membrane over it?
Is ShaliPrime WP SB a waterproofing coat on its own?
What pack size and shelf life does it come in?
How we position STP ShaliPrime WP SB
ShaliPrime WP SB is the first coat in an STP liquid-membrane system, so it pairs naturally with STP’s own membranes such as the ShaliBitumen / Super Thermolay APP membrane range and liquid PU and acrylic waterproofing coatings from the ShaliSeal and ShaliUrethane families. Where a project needs a low-odour, low-VOC primer for enclosed or occupied spaces, point the specifier to its water-based sibling, ShaliPrime WP WB, which offers the same anti-root function without the solvent. Space Arc also carries equivalent membrane-priming solutions across our other principals, so for Dr. Fixit or Fosroc-based systems we can supply the matching primer and membrane from within the same brand family to keep the specification consistent and warranty-clean.
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