Adhesives and Tile Grout Types

Most tile failures in Indian homes have nothing to do with the tile. A floor that sounds hollow when tapped, a wall tile that pops off in the second summer, a vitrified floor that lifts into a tent along the middle of a room, grout that turns black in a year in the bathroom, a shower wall that leaks into the bedroom behind it — almost all of these come from the material under and between the tiles, and from the way it was applied. The tile is usually the most expensive and most carefully chosen part of the job; the adhesive and grout are chosen by the contractor, often on price, and rarely discussed with the owner.

That made sense when Indian tiles were porous ceramic and floors were laid on a thick bed of cement mortar. It does not make sense today. Vitrified and porcelain tiles absorb almost no water, slabs of 1200 × 2400 mm are common, tiles are laid on old tiles during renovations, and kitchens and bathrooms are expected to stay spotless for years. Each of these needs a specific adhesive and a specific grout, and the bag labels — C1, C2TE, S1, CG2WA, RG — are a code that very few homeowners, and not all contractors, can read.

This article decodes that label. It explains why cement mortar no longer works for modern tiles, sets out the adhesive classes used in India and internationally, compares cement, polymer-modified and epoxy grouts, gives trowel sizes, joint widths, coverage and movement-joint rules, and ends with indicative October 2026 costs and a checklist for a tiling quotation. It complements Aaditya Interior's articles on tile laying cost and on grout cleaning and repair.

From mortar bed to thin-bed adhesive

For most of the twentieth century, Indian floors were tiled the same way they had been laid with stone and mosaic: a bed of cement and sand mortar, typically about 20–40 mm thick, spread on the slab or a base course, with a cement slurry poured over it and the tile tapped into place. Joints were filled with white or grey cement, sometimes tinted with pigment to match the tile. Wall tiles were fixed with a similar mortar dab. The method worked because the tiles — red oxide, mosaic, ceramic and natural stone — were porous. The cement paste soaked into the back of the tile, crystallised in its pores and locked it in place mechanically.

Vitrified tiles broke that system. A vitrified or porcelain tile is fired until its body becomes glass-like, and its water absorption is typically 0.5 per cent or less. Cement paste cannot soak into it, so a vitrified tile laid on cement mortar is held mainly by friction and suction. It may feel solid for a while, but differential movement between the tile, the mortar and the slab — from temperature, moisture and the building settling — eventually breaks the weak bond. The result is the hollow sound that so many owners of flats built in the 2000s know well, followed by cracks and lifting.

The answer, developed in Europe and now standard in India, is the thin-bed tile adhesive: a factory-made powder of cement, graded fine sand and polymers, mixed with water and spread with a notched trowel in a bed of about 3–6 mm on a flat, prepared surface. The polymers give the adhesive genuine chemical and film adhesion to dense tile backs, flexibility to absorb small movements, and water retention so that the cement cures properly in a thin layer. Laying on adhesive needs a flat substrate — the screed or plaster now does the levelling that the thick mortar bed used to do — but it is faster, uses less material and, when done properly, gives a far stronger and more durable bond.

Reading the adhesive bag: C1, C2 and the extra letters

Tile adhesives are classified by an international system set out in EN 12004 and ISO 13007, and many Indian brands print these classes on their bags alongside their type under the Indian standard IS 15477, the specification for adhesives for ceramic tiles and mosaics. The first letter tells you the chemistry. C means cementitious — the powder adhesives used on almost all Indian sites. D means dispersion, a ready-mixed paste adhesive used mainly for wall tiles in dry interiors. R means reaction resin, usually epoxy or polyurethane, used for special substrates such as metal, wood or chemically exposed floors.

The number after the letter tells you the strength. A C1 adhesive is a normal adhesive with a minimum tensile adhesion strength of 0.5 N/mm² in the standard tests. A C2 adhesive is an improved adhesive, with a minimum of 1.0 N/mm² — twice the bond — after normal curing, water immersion, heat ageing and freeze-thaw cycles. For dense vitrified tiles, wall tiles and anything outdoors or in wet areas, C2 is the sensible minimum.

The letters after that describe special behaviour. F means fast-setting, useful where floors must be back in use within hours. T means reduced slip: a tile on a wall will not slide down more than 0.5 mm, so wall tiling can start from the top without spacers taking all the weight. E means extended open time: the spread adhesive stays workable for at least 30 minutes, which helps in hot, dry conditions — an Indian summer on a terrace or a west-facing wall can skin over a normal adhesive in minutes. S1 and S2 describe deformability: an S1 adhesive is deformable, with a transverse deformation of at least 2.5 mm in the standard test, and S2 is highly deformable, at least 5 mm. Deformable adhesives absorb movement from heat, shrinkage and flexible substrates, and they are the specification for large slabs, external facades, floors in direct sun, underfloor heating and tile-on-tile renovation.

Choosing the right adhesive for the job

The right adhesive depends on four things: the tile (its absorption, size and weight), the substrate (concrete, plaster, gypsum, old tile, board or membrane), the location (indoor dry, indoor wet, exterior, sun-exposed) and the expected movement. A simple way to choose is to start at C2T for any vitrified tile, and then go up a step for each extra demand: add E for hot conditions and large areas, add S1 for large formats, exteriors, sun, heat or tile-on-tile, and consider S2 or a resin adhesive for flexible substrates.

Substrates deserve as much attention as tiles. New cement plaster or screed must be cured, sound, clean and reasonably flat — tolerances of about 3 mm under a 2 m straightedge are commonly specified for large formats. Gypsum plaster usually needs a primer before cement-based adhesives. Old tiles must be firmly bonded, degreased and abraded, and need a C2 S1 adhesive, often with a primer. Waterproofing membranes in bathrooms and terraces must be compatible with the adhesive and fully cured; the waterproofing and adhesive should ideally come from the same system. Painted walls should be stripped back to plaster — tiling over paint is a common cause of wall tiles falling.

Laying it right: trowel, bed and coverage

Even the best adhesive fails if it is applied badly. The most common fault on Indian sites is spot-bonding: dabs of adhesive at the corners and centre of the tile, leaving voids underneath. It is quick and uses less material, but it leaves the tile hollow, prone to cracking under point loads and, in wet areas, full of cavities where water collects. Proper practice is to comb the adhesive onto the substrate with a notched trowel in straight parallel lines, press the tile in with a sliding motion across the ridges to collapse them, and for large tiles, also butter the back of the tile with a thin coat — the double-spread or back-buttering method.

The notch size sets the bed thickness. Small tiles up to about 300 mm are commonly laid with a 6 mm notch; tiles around 600 × 600 mm with an 8–10 mm notch; and 600 × 1200 mm tiles and slabs with a 10–12 mm notch plus back-buttering. Industry guidance commonly cites at least 80 per cent contact for interior dry floors and 95 per cent or more for wet areas, exteriors and large formats; the simple site check is to lift a freshly laid tile occasionally and look at the back. Bed thickness after pressing should normally stay within the maker's range — about 3–6 mm for thin-bed products; adhesive is not a levelling compound.

Consumption figures are typical for flat substrates and vary with the substrate's flatness, the tile's back profile and the product; uneven floors consume much more. The practical lesson for budgeting is that large-format tiles use roughly twice the adhesive per square foot of small tiles, which is one reason slab work is quoted separately.

Grout types: what goes between the tiles

Grout fills the joints between tiles. It locks the edges, keeps dirt and water out of the joint and completes the look of the surface. Like adhesives, grouts are classified internationally, in EN 13888 and ISO 13007-3. Cementitious grouts are CG: CG1 is a normal grout, and CG2 is an improved grout that can carry extra letters — W for reduced water absorption and A for high abrasion resistance. A CG2WA grout is therefore an improved cement grout that absorbs less water and resists wear better. Reaction resin grouts, usually epoxy, are classed RG.

Cement grout

Traditional cement grout is white or grey cement, sometimes with pigment, mixed with water and pressed into the joints. Modern factory-made cementitious grouts add fine graded fillers, polymers and pigments for better colour consistency, lower shrinkage and lower absorption. Cement grout is cheap, easy to apply and easy to clean off the tile face, but it is porous: in bathrooms and kitchens it absorbs water, soap, oil and turmeric, darkens, and can grow mould. Sanded cement grouts, with fine sand, are used for wider joints of about 3 mm and above; unsanded or fine grouts for narrow joints. Sealing a cement grout after it cures improves its stain resistance but must be repeated periodically.

Epoxy grout

Epoxy grout is a two- or three-part system of epoxy resin, hardener and coloured filler. Once cured, it is effectively waterproof, stain-proof, chemically resistant and very hard. It is the right grout for kitchens, bathrooms, shower areas, swimming pools, commercial kitchens, hospitals and anywhere hygiene matters. It is also more demanding to apply: it has a short working time, sticks stubbornly to the tile face if not cleaned off within the maker's window, and leaves a permanent haze if done badly. Its material cost is several times that of cement grout, but on a typical bathroom it is still a small fraction of the cost of the tiles. Epoxy grouts in light colours can yellow in strong sunlight unless they are UV-stable; exterior use needs a grade made for it.

Other grouts and fillers

Ready-mixed grouts, based on acrylic, urethane or hybrid resins, come in tubs and need no mixing; they are convenient for small repairs and some walls. Metallic and glitter grouts are epoxy grouts with decorative fillers, used for feature walls. Silicone sealant is not a grout: it belongs only in movement joints — at wall-to-floor junctions, around sanitaryware, at changes of plane and in field movement joints — where the surface must flex. Grout in these places cracks within months.

Joint widths and movement joints

Tile joints are not just cosmetic. They absorb the small size variations between tiles, accommodate small movements and give grout enough body to hold. Rectified tiles, which are ground to precise sizes, can be laid with narrow joints of about 2–3 mm, and slabs with about 1.5–2 mm. Non-rectified tiles need about 3–5 mm. Outdoor tiles, terraces and areas in direct sun need wider joints — about 3–6 mm or more — to accommodate thermal movement. Zero-joint or butt-jointed tiling, often requested for a seamless look, is a common cause of tenting and edge chipping and is not recommended by tile and adhesive manufacturers.

Movement joints are the other half of the story. A tiled floor expands and contracts with temperature and moisture, and the building itself moves. Without somewhere for that movement to go, stresses build up until tiles crack or lift — the familiar tenting of a vitrified floor along the middle of a room, often after a hot spell. Perimeter joints of about 5–10 mm should be left at every wall and column and hidden under the skirting. Field movement joints, filled with a flexible sealant or a profile, are commonly placed at about 6–7.5 m intervals in interior floors and about 2.5–3.6 m outdoors or in direct sun, following typical industry guidance; they should also follow any structural joints in the slab. The tile designer or adhesive maker's specification should set the exact layout.

What adhesive and grout cost

For budgeting, adhesive and grout are small items compared with tiles and labour, but they are where false economies hurt most. The figures below are indicative October 2026 ranges in Surat and similar cities; branded products and specialist grades cost more. They are consistent with the tile laying rates used across this site: standard laying labour of about ₹25–40 per sq ft, with slab laying at about ₹40–80 per sq ft and slab-grade C2 S1 adhesive at about ₹20–35 per sq ft.

A worked example shows the scale. A bathroom with about 150 sq ft of wall and floor tiles in 300 × 600 mm format might use three or four bags of C2TE adhesive, about ₹1,800–4,000, and cement grout worth a few hundred rupees. Switching to epoxy grout adds about ₹1,200–3,750 in material and ₹1,500–3,750 in skilled labour — a few thousand rupees in all, on a bathroom whose tiles, waterproofing and fittings cost many times that. In wet areas, the upgrade almost always pays for itself in cleaning time and appearance.

Where tile fixing is heading

The direction is clear: thinner, larger and more engineered. Tiles and slabs keep getting bigger and thinner, which pushes adhesives towards higher deformability and better wetting, and pushes installers towards levelling systems, suction lifters and specialised trowels. Low-dust adhesives, lighter adhesives with lightweight fillers, rapid-setting systems for quick renovations, and adhesives with lower embodied carbon are all now offered by major manufacturers. Waterproofing, adhesive and grout increasingly come as matched systems with a single warranty. For homeowners, the change that matters most is simpler: tile fixing is now a specified material system, and it should be written into the quotation by name and class rather than left as cement and labour.

Rules for a tiling specification

• Never lay vitrified tiles on plain cement mortar or slurry; specify a polymer-modified adhesive of at least C2T.
• Specify C2TE S1 for tiles 600 × 1200 mm and larger, slabs, terraces, exteriors, sun-exposed floors and tile-on-tile work.
• Write the adhesive and grout brand and class into the quotation, not just ‘adhesive’.
• Insist on combed full-bed application and back-buttering for large tiles — no spot-bonding.
• Use epoxy grout in kitchens, bathrooms and showers; CG2 cementitious grout is fine in dry rooms.
• Keep joints of about 2–3 mm for rectified tiles and wider outdoors; avoid zero-joint tiling.
• Leave a 5–10 mm perimeter gap under skirtings and plan field movement joints; use silicone, not grout, at junctions.
• Let the substrate cure and check its flatness before tiling; prime gypsum and old tiles as the maker specifies.

Frequently asked questions

Which tile adhesive is best for vitrified tiles?

A polymer-modified cementitious adhesive of class C2T or C2TE for normal sizes up to about 600 × 600 mm, and C2TE S1 for 600 × 1200 mm, slabs, outdoor areas and tile-on-tile. Plain cement mortar does not bond reliably to dense vitrified tiles.

What is the difference between C1 and C2 tile adhesive?

C1 is a normal adhesive with a minimum tensile adhesion of 0.5 N/mm²; C2 is an improved adhesive with at least 1.0 N/mm² after all the standard ageing tests. C2 is the safe choice for vitrified tiles, walls, wet areas and exteriors.

Is epoxy grout better than cement grout?

In wet and stain-prone areas, yes: epoxy grout is effectively waterproof and stain-proof, while cement grout absorbs water and stains. In dry rooms, a good CG2 cement grout is adequate and much cheaper. Epoxy needs skilled application to avoid haze.

How many square feet does a 20 kg bag of tile adhesive cover?

Roughly 40–55 sq ft for wall tiles and small floor tiles with a 6–8 mm notch, about 35–45 sq ft for 600 × 600 mm tiles, and about 25–35 sq ft for 600 × 1200 mm tiles with back-buttering, on a flat substrate. Uneven floors use more.

Can I lay new tiles over old tiles?

Often, yes, if the old tiles are firmly bonded, level and free of grease. Use a primer and a deformable C2 S1 adhesive, and check that the raised floor level still clears doors, thresholds and drains. Hollow or cracked old tiles must be removed first.