Top Mistakes Builders Make When Specifying Tiles

Most tile failures on a construction site are not installation failures. A crew that lays tile every day rarely gets the actual laying wrong. What goes wrong far more often is the specification that reached them in the first place, a tile chosen for its finish and price without the technical checks that decide whether it survives the space it is going into.

The gap usually shows up months after handover, as cracked tiles over a slab joint, a slippery entrance lobby, or a batch mismatch that a client notices immediately and a contractor cannot fully explain. Almost all of these trace back to one of the same ten specification mistakes, repeated across projects of every size.

Mistake 1: Specifying by Look Alone, Not by Water Absorption Group

A tile catalogue photo tells you nothing about how the tile performs once water is involved. Every ceramic and vitrified tile falls into a water absorption group, from Group BIa at 0.5% or lower up to higher-absorption groups suited only to dry interior walls.

A specification that simply says vitrified floor tile, 600x600mm leaves the door open for a contractor to supply whatever fits that description at the lowest price, including a tile with far higher absorption than the space needs. Naming the water absorption group explicitly, and asking for it on the supplier's test certificate, closes that gap.

Mistake 2: Treating PEI Rating as Optional Paperwork

PEI rating measures surface abrasion resistance, essentially how well a tile's glaze holds up against foot traffic over years of use. It has nothing to do with strength or water resistance, which is exactly why it gets skipped so often, it does not show up as an obvious defect on day one.

A PEI Class II tile can look identical to a PEI Class IV tile in a showroom sample. Used on a busy lobby or corridor floor, the lower-rated tile visibly dulls and scratches within a couple of years while the higher-rated one does not. Match PEI rating to actual foot traffic, not to whichever tile the client liked in the showroom.

Mistake 3: Confusing Wall Tile Specifications with Floor Tile Loads

Wall tiles are manufactured thinner and are not rated to carry foot traffic or point loads. This sounds obvious stated directly, yet it remains one of the most common site substitutions, usually made under time pressure when a matching floor tile from the same range is out of stock, and the wall variant looks close enough.

The result is cracking under normal walking load within months. If a design calls for a unified look across wall and floor, confirm both a floor-rated and wall-rated version exist in that exact design before finalising the specification, not after the wall tile has already been ordered.

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Mistake 4: Skipping Slip Resistance Ratings for Wet and Outdoor Zones

Slip resistance is tested and rated separately from every other tile property, commonly expressed as an R rating from a wet ramp test. Bathrooms, pool decks, entrance lobbies exposed to rain, and any sloped or outdoor surface all need a minimum R rating specified in writing, not left to the tile's general description as anti-skid.

Anti-skid printed on a box has no fixed technical meaning on its own. Always ask for the specific R value and the test standard it was measured against before approving a tile for a wet or outdoor zone.

Mistake 5: Leaving Out Movement Joints in Large Tiled Fields

Tile assemblies are rigid, but the slab beneath them expands and contracts with temperature and moisture. Without movement joints at regular intervals, especially across large uninterrupted floor fields exposed to direct sun, that stress has nowhere to go and transfers straight into the tile and grout.

This shows up as cracking, or in worse cases, as tiles lifting off the substrate entirely in a phenomenon installers call tenting. Movement joints should be placed at the perimeter, at every change of plane, directly over any existing joint in the substrate, and at set intervals across large open fields, not added as an afterthought once cracks appear.

Mistake 6: Ignoring Batch and Calibre Variation on Bulk Orders

Every production run of tile carries some variation in shade and exact size, referred to as batch and calibre. A specification that does not require single-batch supply for a continuous area invites visible shade mismatches once tiles from two different runs end up side by side.

This risk grows with order size and timeline. A project phased over several months is far more likely to need a repeat order after the original batch has sold out, so it is worth ordering a small buffer stock upfront specifically to cover future repairs and phase two work from the same batch.

Mistake 7: Under-Specifying Thickness for Load-Bearing Areas

Thickness requirements differ sharply by end use, and a specification written for one area sometimes gets copied across an entire project without adjustment. A 7 to 9mm tile suited to a bedroom floor is not suited to a driveway or a loading area that regularly carries vehicle weight.

Vehicle-accessible areas typically need tiles in the 12 to 20mm range depending on expected load. Confirm thickness against actual use, not against whatever thickness happened to be in stock for the rest of the project.

Mistake 8: Leaving Grout and Adhesive Choice to the Contractor

Grout and adhesive are frequently treated as minor line items decided on site rather than specified upfront, yet they directly affect how well the tile performs. Standard cement grout stains and supports algae growth in wet or outdoor areas where epoxy grout would resist both.

Similarly, large format tiles need a polymer-modified adhesive with full coverage, not a standard thin-set intended for smaller tiles, or the tile risks hollow spots that crack under point load later. Specify both explicitly rather than leaving them to whatever the contractor has on hand.

Mistake 9: Not Budgeting Wastage or Batch Discontinuation Risk in the BOQ

A Bill of Quantities calculated on exact area coverage, with no wastage allowance, routinely runs short mid-project once cutting losses around corners, doors, and pattern layouts are accounted for. A standard 8 to 10% wastage margin should be built into every tile line item from the outset.

A second, less obvious risk is batch discontinuation. If a project is phased or likely to need future repairs, ordering enough surplus stock at the outset, and storing it properly, is far cheaper than trying to source a matching batch a year later once the original run is no longer in production.

Mistake 10: Approving Tile Selection Without a Written Specification

The single mistake that makes all the others more likely is skipping a written specification document altogether. A verbal agreement on a tile choice, or an approval based on a single showroom sample, leaves no enforceable reference point if the wrong batch, wrong PEI class, or wrong water absorption group shows up on site.

A written specification does not need to be long. It needs to name the exact tile code, the standard it complies with, and the technical values that matter for that specific location, so that any dispute later has something concrete to check against.

A Quick Reference for What Every Tile Specification Should State

Regardless of project size, a tile specification line item is only enforceable if it states the following, rather than describing the tile by appearance alone.

Getting the Specification Right the First Time

A tile specification is a technical document, not a design mood board. Treating it that way, with named standards, exact values, and a written record, is what actually prevents the failures that show up months after a project is handed over.

If you are sourcing tiles for a project and need supplier documentation on water absorption, PEI rating, or IS compliance, TilesFinders connects builders and contractors with verified dealers on tilesfinders.com who can provide these certificates upfront.