Tile Adhesive Specifications: What to Write Into the BOQ

A bill of quantities line that reads “supply and fix tiles with approved tile adhesive” is not a specification. It is an invitation to substitute, and it is the single most common reason a project ends up with an interior-grade product on a facade or a Type 1 adhesive under vitrified tiles. The contractor is not usually at fault. Given a line with no performance requirement in it, the cheapest compliant product is the rational choice, and almost everything is compliant with a line that specifies nothing. Writing proper tile adhesive specifications takes a few extra lines and removes that ambiguity entirely. This guide sets out what those lines should contain and why each one matters.

Key Takeaways

• Write tile adhesive specifications by performance class, not brand alone, so the requirement survives substitution.

• Name the IS 15477:2019 type and the ISO 13007 / EN 12004 code for every application area.

• Write a separate line for each condition: interior floor, wet area, exterior, large format, difficult substrate.

• State substrate preparation and flatness tolerance, since adhesive cannot correct a bad base.

• Specify joint widths and movement joints in the same section, not in a separate trade.

• Require TDS, MSDS and test certificates as submittals before material is ordered.

• Include a site verification step so compliance is checked during work, not after.

Why vague tile adhesive specifications cost money

Everything is “approved” when nothing is specified

Tile adhesive specifications that name no class leave approval as the only test. Without a class or a standard in the line, the only test a product has to pass is that someone approves it. Approval on site is usually granted under time pressure by whoever is available, and the result is a product chosen on availability and price rather than suitability.

Substitution happens at the worst moment

Material substitution requests tend to arrive late, when the programme is tight and the original grade is out of stock locally. A specification with a performance class in it gives the reviewer an objective test. A specification without one gives them nothing to say no with.

The failure surfaces years later

Adhesive failures rarely appear during the defect liability period. Hollow floors, debonded cladding and cracked large formats typically surface after two or three seasons of thermal cycling, by which point establishing responsibility is difficult. The specification is the cheapest point at which to prevent all of that.

Classifications your tile adhesive specifications must reference

IS 15477:2019

The Indian standard sorts adhesives into types. Type 1 is the basic cementitious adhesive for interior ceramic work. Type 2 is improved and suited to low-porosity tiles such as vitrified, including wet areas. Type 3 is a high-polymer adhesive for demanding conditions such as exteriors and tile-on-tile. Type 4 covers highly deformable adhesives for large slabs and substrates that move.

Suffixes matter too. A “T” indicates slip resistance, “S1” and “S2” indicate deformability, with S2 being the more flexible.

ISO 13007 / EN 12004

The international code reads like C2TES1: C for cementitious, 2 for improved performance, T for slip resistance, E for extended open time, and S1 or S2 for deformability. Quoting both the Indian and international classification makes the requirement unambiguous for any bidder.

Worked examples from a real range

For reference, VX-2 confirms to IS 15477:2019 Type 2T and to EN 12004 / ISO 13007 as C2TE. EX-5 is classified C2TES1 and exceeds IS 15477:2019 Type 3TS1. LX-7 Super Flex S2 is IS 15477:2019 Type 4TS2 and C2TES2 per EN 12004:2017. Those are the kinds of statements tile adhesive specifications should be able to test a submittal against.

Writing tile adhesive specifications area by area

Give each condition its own line. A single global line cannot serve all of them.

Interior ceramic, dry areas

Polymer-modified cementitious adhesive to IS 15477:2019 Type 1 or better. Grey acceptable; white where tile is light-coloured or translucent. Typical products: CX-1 grey, CX-2 white.

Vitrified tiles and wet areas

Polymer-modified cementitious adhesive to IS 15477:2019 Type 2T minimum, ISO 13007 class C2TE, suitable for showers, wet areas and submerged applications. Typical products: VX-1 grey, VX-2 white. Note that VX-2 is not recommended for direct use onto gypsum plaster wall finishes, paint or metal, and is not suitable for tiles and stones with mesh backing — worth writing into the substrate clause.

Exteriors, facades and tile-on-tile

High-polymer adhesive exceeding IS 15477:2019 Type 3TS1, ISO 13007 class C2TES1 minimum, with stated deformability. Typical product: EX-5. Our exterior wall tile and stone cladding guide covers the additional facade requirements.

Large format tiles and slabs

Highly deformable adhesive to IS 15477:2019 Type 4TS2, ISO 13007 class C2TES2, sag and slump resistant. Typical products: LX-7 S1 and LX-7 Super Flex S2. Specify back-buttering and a 10 to 12 mm notch on floors, 8 to 10 mm on walls.

Metal, plywood and drywall substrates

Two-component polyurethane adhesive suitable for non-cementitious substrates. Typical product: PUA-100. Cementitious adhesives should be expressly excluded for these substrates.

Clauses tile adhesive specifications commonly leave out

Substrate preparation and tolerance

State that substrates must be fully cured, structurally sound, clean and free of dust, oil, curing compound, laitance and loose material. Give a flatness tolerance appropriate to the tile size, since the tolerance that passes for small ceramic will not serve a large slab. Make clear that levelling is a screed operation, not an adhesive one, and that maximum bed thickness per the manufacturer’s TDS must be observed.

Joint width and movement joints

Specify joint widths per area and require movement joints at floor levels, changes of substrate, internal corners, and to break large uninterrupted areas into panels. Interior slab joints are typically 2 to 3 mm; exterior joints should be more generous. Specify that tile spacers are used, and a tile levelling system for large formats.

Grout, as part of the same system

Specify the joint filler alongside the adhesive rather than in a separate section, including stain and chemical resistance requirements for wet and commercial areas, the joint width range the grout is formulated for, and UV resistance where joints are in direct sun. See the grouts range and our epoxy grout versus cement grout comparison.

Structural support for heavy cladding

For heavy stone or work at height, state that the substrate must be verified as capable of carrying the weight of the covering, and that additional mechanical support or fasteners are to be provided where the site engineer requires them. Adhesive fixing has limits, and the specification should say who decides where they lie.

Submittals and site verification

• Require, before any material is ordered:

• Technical Data Sheet for each proposed product

• Material Safety Data Sheet

• Test certificates supporting the stated IS and ISO classifications

• Published coverage or consumption data in kg per square metre per millimetre

• Confirmation of substrate suitability and any stated limitations

During installation, require periodic verification that adhesive transfer across the back of a lifted tile is complete, since that is the only practical on-site test of bed quality, and it catches problems while they are still cheap to fix.

Reference data can be pulled from the TDS library and the standards and certifications page, and the laying instructions page sets out the application method a specification can cite.