STP ShaliFlex PU T
Two-component, 100% solid polyurethane adhesive rated R2T for fixing marble, natural stone and large-format tiles where the substrate moves, vibrates or stays damp.
What is it?
A two-part, 100% solid polyurethane tile adhesive from STP, classified R2T and IS 15477-2019 Type 5 – the highest deformability grade for reaction-cured adhesives.
Where is it used?
Indoor and outdoor floors and walls: marble and natural stone, large-format and low-thickness slabs, porcelain, and tiles over difficult substrates like wood, metal, PVC or existing resin floors.
Why use it?
It flexes with the substrate instead of cracking, has zero shrinkage or solvent, holds tiles vertically with almost no slip, and bonds to surfaces cement adhesives cannot grip.
How is it applied?
Mix the pre-batched 3.2 kg + 0.8 kg packs (4:1 by weight) with a slow helicoidal stirrer, comb onto the substrate with the right notched trowel, and bed the tile within the 50-minute open time.
About STP ShaliFlex PU T
STP ShaliFlex PU T sits at the top of the tile-fixing ladder. It is a two-component, 100% solid polyurethane adhesive – meaning there is no water and no solvent to evaporate, so the bed does not shrink as it cures. That single property is what lets it hold heavy marble and large slabs on surfaces that would defeat an ordinary cement-based adhesive. STP classifies it as R2T under EN 12004 and as IS 15477-2019 Type 5, the categories reserved for improved, deformable, non-slip reaction adhesives. In plain terms, it is engineered for the jobs where movement, moisture or an awkward substrate is the real problem, not just the tile.
Where cementitious adhesives depend on a stable, porous, fully-cured masonry background, ShaliFlex PU T is comfortable on the surfaces that give tilers trouble – timber and plywood, metal, rubber, PVC, linoleum, glass, and existing resin or glazed floors. It is particularly valued for marble and light natural stone that stain or sag when a water-based adhesive keeps them damp, because the PU chemistry carries no water into the stone. Supplied by Space Arc Engineering as an authorised STP distributor across Delhi NCR and pan-India, it is a specialist product: for routine ceramic on a sound screed, STP’s own cement-based ShaliTile Fix range is the more economical choice.
The technical insight
The performance comes from the polyurethane network itself. Once parts A and B react, they form a cured film that stays elastic rather than setting rigid like a cement mortar. When the substrate expands, contracts or vibrates, that elastic bed absorbs the differential movement and shears internally instead of transmitting stress into the tile or the bond line – which is exactly what the R2T “deformable” rating certifies. Being 100% solids, nothing leaves the adhesive during cure, so there is no drying shrinkage to pull the tile off-line and no solvent to attack sensitive stone. The 4:1 fixed ratio is not a suggestion: the crosslink density depends on getting parts A and B correct, which is why STP pre-batches the 3.2 + 0.8 kg packs and warns against using partial quantities. The result is a bond that pulls off concrete at over 3 MPa (failing in the concrete, not the glue) and retains around 2.0 N/mm2 shear strength even after water immersion.
Where it is used
- Fixing marble, granite and light natural stone that stains or sags with water-based adhesives
- Large-format and low-thickness porcelain slabs on floors and facades
- Tiling over vibrating or deflecting substrates such as timber, plywood and metal decks
- External floors and walls exposed to thermal movement and weather cycling
- Tile-over-tile and tile-over-resin renovation without hacking out the old surface
- Bonding to non-absorbent backgrounds – PVC, rubber, linoleum and glass surfaces
- High-traffic commercial and industrial floors needing an elastic, high-adhesion bed
- Wet and humidity-prone areas where cement adhesives risk staining natural stone
Key advantages
- R2T deformable grade – flexes with substrate movement instead of cracking the tile
- 100% solid PU with no water or solvent, so zero shrinkage and no staining of stone
- Bonds to difficult non-porous substrates that cement adhesives cannot grip
- Vertical slip of 0.5 mm or less holds tiles in position on walls without sagging
- Generous working window: 50-minute open time and over 40 minutes adjustability
- High bond strength – over 3 MPa pull-off on concrete, with concrete failure
- Retains strong shear adhesion (about 2.0 N/mm2) even after water immersion
- Pre-batched 4 kg packs remove the guesswork from the critical mix ratio
Limitations & considerations
- Premium-priced specialist product – overkill for routine ceramic on a sound screed, where cement-based ShaliTile Fix is more economical
- Fixed 4:1 mix ratio must be respected in full; partial quantities lead to incorrect cure and failure
- Cannot be used on polystyrene, on transparent glass tiles, or over surfaces subject to rising damp or not fully cured
- Short usable pot of about 1 hour at 27 C means only mix what the crew can lay quickly
- Flammable during application and requires good ventilation, gloves, goggles and a mask
- Only supplied in a 4 kg unit pack, so bulk floor areas need careful quantity planning
Selection & best practice
Start with a substrate that is compact, clean and fully cured – free of dust, oil, laitance and any rising damp, with hygrometric shrinkage complete and uneven areas already levelled. Mix parts A and B from the bottom up with a low-speed (around 400 rpm) helicoidal stirrer at the full 3.2 : 0.8 ratio until the colour is uniform, and never split the pack. Only prepare what the team can consume within an hour at 27 C. Apply with the smooth edge first to key the product to the background, then comb with a notched trowel sized to the tile – trowel no. 4 for mosaic and small formats, no. 5 for normal tiles, larger notches for slabs and stone. For external work, heavy traffic or any high-elasticity requirement, back-butter with the double-spread technique to achieve full contact behind the tile. Work between +10 C and +40 C substrate and ambient, keep relative humidity at 80% or below, and clean fresh residue off tools with STP Thinner before it cures.
Specifications
| Chemistry / Type | Two-component 100% solid polyurethane reaction adhesive |
| Classification | R2T (EN 12004) & IS 15477-2019 Type 5 |
| Mixing ratio | Component A : Component B = 4:1 by weight |
| Pack size | 4 kg unit (3.2 kg A + 0.8 kg B) |
| Coverage | 2.5 kg/m2 (small tiles, trowel 4); 3.5 kg/m2 (normal, trowel 5); 5 kg/m2 (large tiles, marble, stone) |
| Open time / Adjustability | 50 minutes / greater than 40 minutes |
| Adhesive thickness | 2 – 10 mm |
| Pull-off adhesion on concrete | Greater than 3 MPa (concrete failure) |
| Set to light foot traffic / Ready to use | 12 – 24 hours / 7 days |
| Shelf life | 12 months unopened at 5 – 38 C |
Industry use cases
Luxury Residential & Hospitality
Fixing imported marble and large-format porcelain slabs in lobbies, bathrooms and facades where water-based adhesives would stain the stone or fail to bond low-thickness slabs.
Commercial & Industrial Floors
Elastic, high-adhesion bedding for tiles on vibrating or high-traffic floors where a rigid cement bond would crack under repeated dynamic loading.
Renovation & Retrofit
Tile-over-tile and tile-over-resin overlays that avoid the cost and disruption of hacking out an existing floor, bonding directly to the old surface.
External Cladding & Facades
Outdoor walls and floors subject to thermal cycling and weather, where R2T deformability absorbs movement between substrate and tile.
Difficult Substrates
Tiling onto timber, plywood, metal decks, PVC and other non-absorbent backgrounds that cement adhesives simply cannot grip reliably.
Frequently asked questions
What does the R2T rating actually mean for my project?
How much ShaliFlex PU T do I need per square metre?
Can I use it to fix marble and light natural stone?
Do I have to use the whole 4 kg pack at once?
Which substrates should I avoid?
Is it a straight swap for cement-based tile adhesive?
How we position STP ShaliFlex PU T
ShaliFlex PU T is the top of STP’s tile-fixing range – reach for it when movement, moisture or an awkward substrate rules out a cement adhesive. For everyday ceramic and vitrified tiling on a sound screed, the more economical cement-based ShaliTile Fix 100, 200, 300 and 400 grades from the same STP family are the right call, with ShaliTile Grout and ShaliTile Grout E to finish the joints. If you prefer a comparable deformable/flex adhesive from another line we stock, Sika SikaCeram-288 Flex S1 and UltraTech Tilefixo X’TRAPLUS are solid alternatives; talk to the Space Arc technical desk and we will match the adhesive to the tile, substrate and exposure.
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