Large format tiles have become the default choice for a clean, modern floor or wall, and for good reason: fewer grout lines make a room look bigger and calmer. But they are also the least forgiving format to fit. Get the substrate or the adhesive wrong and you will see every high spot as a raised tile edge. This guide explains what counts as a large format tile, the real pros and cons, and how the job should be done to meet the relevant British Standards.
As a Bromley tiling firm we fit these every week, so this is written from the working side of the trowel rather than a showroom brochure.
What counts as a large format tile?
The Tile Association treats a tile as large format when at least one side is over 600mm. In practice the fitting challenges start earlier: once a tile passes about 450mm on one edge, and especially with dense porcelain, you need to change how you prepare and bed it. Common sizes now run from 600 x 600mm through 600 x 1200mm and up to panel-style slabs of 1200 x 2400mm and larger.
The appeal is straightforward. A 600 x 1200mm porcelain covers the same area as eight 300 x 300mm tiles with a fraction of the grout, so a bathroom or kitchen reads as one continuous surface. The trade-off is weight, handling and the flatness the format demands.
The pros of large format tiles
- Fewer grout joints. Less grout means a cleaner look and less to keep clean. Grout is the part of a tiled surface that stains and needs sealing, so cutting the amount of it is a genuine maintenance win.
- A sense of space. In a small Bromley bathroom, running one tile size up the wall and across the floor makes the room feel larger and less busy.
- Fast coverage on sound floors. On a large, flat, solid floor a big tile covers ground quickly once the preparation is done.
- Rectified edges. Most large format porcelain is rectified, meaning the edges are machined dead straight, so you can run tight, uniform joints.
- Strong, low-porosity surface. Porcelain in these sizes is hard-wearing and water-resistant, which suits wet rooms, kitchens and hallways.
The cons you should know before you buy
- They expose an uneven base. A big rigid tile cannot follow a wavy floor. Any dip or hump shows up as lippage, the trade word for a height difference between neighbouring tiles.
- Handling and cutting are harder. Slabs are heavy and can flex or snap if lifted wrongly. Cutting usually needs a proper rail cutter or a wet saw with a continuous-rim blade, not a small hand cutter.
- Labour costs more. The preparation, levelling and two-person handling mean the labour rate per square metre is higher than for standard tiles, even though there are fewer to lay.
- Waste is dearer. A cracked large slab wastes far more material and money than a broken 300mm tile.
Substrate preparation is where the job is won or lost
British Standard BS 5385 sets the flatness a tiled surface should be laid to. For large format work the background should not deviate by more than 3mm under a 2 metre straight edge. That is a tight tolerance, and few floors meet it out of the box.
On a screed or concrete floor that means using a self-levelling compound to take out the dips. On a timber floor it means over-boarding with a suitable tile backer board and, where there is movement or underfloor heating, an uncoupling (anti-fracture) membrane. Skipping this stage is the single most common cause of cracked or drummy large format tiles.
Adhesive, coverage and beating lippage
Large tiles must be bedded solidly. BS 5385 calls for a minimum of 80% adhesive coverage in dry internal areas and 95% in wet areas, externally, and under heavy-duty or large format tiles, with no voids under corners where a foot or a dropped object could crack the tile.
Achieving that under a big slab means the “double bond” or back-buttering method: comb adhesive onto the floor with the correct notched trowel and also skim the back of the tile, then lay it and beat it in. Use a good quality cement-based adhesive rated at least C2 (an improved adhesive), and choose a flexible S1 grade over underfloor heating, timber or anywhere with movement.
To hold adjacent tiles in the same plane while the adhesive sets, fit a tile levelling system, the clips-and-wedges jigs that clamp tile edges level. On large formats it is close to impossible to meet the BS 5385 lippage tolerance (1mm on joints under 6mm wide, 2mm on wider joints) by eye alone. Levelling clips are not a gimmick here, they are how the standard gets met.
One more detail buyers often miss: the 2018 revision of BS 5385 increased minimum grout joint widths for larger tiles. A hairline joint on a 1200mm tile invites problems, so plan for a joint of at least 3mm and follow the tile maker’s stated minimum.
Should you DIY or hire a tiler?
A confident DIYer can tile a small splashback in standard tiles. Large format floors and walls are a different job. The weight, the flatness tolerance, the solid-bed coverage and the cutting all raise the stakes, and a mistake is expensive because the materials are dear. If you are set on big-format porcelain in a bathroom, wet room or kitchen, it is usually worth getting a professional to at least prepare the base and set out the first course.
If you are planning a project in Bromley or south east London, you can see the range of work we cover on the Bromley Tilers homepage, and the industry guidance referenced here comes from The Tile Association.
Frequently asked questions
What size is classed as a large format tile?
The Tile Association classes a tile as large format when at least one side is longer than 600mm. Fitting challenges tend to begin once a tile is over about 450mm, particularly with dense porcelain.
Do large format tiles need a levelling system?
In practice, yes. To meet the BS 5385 lippage limits of 1mm to 2mm across the surface, a clip-and-wedge levelling system holds neighbouring tiles in the same plane while the adhesive cures. Working by eye alone rarely achieves it on big tiles.
Can you lay large format tiles on a timber floor?
Yes, but the floor must be made rigid and flat first, usually by over-boarding with tile backer board and adding an uncoupling membrane where there is any movement or underfloor heating, then bedding the tiles in a flexible S1 adhesive.
How flat does the floor need to be?
For large format tiling BS 5385 recommends the background deviates by no more than 3mm under a 2 metre straight edge. Most floors need a self-levelling compound or over-boarding to reach that.
Why did my large tiles crack after fitting?
The usual causes are an uneven or moving substrate, voids under the tile from poor adhesive coverage, or a rigid adhesive over underfloor heating. Solid bedding, a flat base and a flexible adhesive prevent it.
Are large format tiles more expensive to fit?
The labour per square metre is higher because of the extra preparation, levelling and two-person handling, even though there are fewer tiles to lay. Material waste from a broken slab also costs more than a broken small tile.