Tile Pattern Layout Planner

Nobody looks at the middle of a tiled floor. The eye goes to the edges, where the last row meets the wall, and it finds one of two things there: cuts of a decent, even width on both sides of the room, or a full tile at one wall and a strip the width of a finger at the other.

Both floors used the same tiles and nearly the same number of them. The difference was made before any adhesive was mixed, by deciding where the pattern starts. That decision is the layout, and it is the cheapest part of a tiling job to get right and the most expensive to get wrong, because it cannot be changed once the first tiles have set.

What the standards actually ask for

The US installation standard for tile, ANSI A108.02, treats layout as workmanship and says so in very few words. As the Ceramic Tile Education Foundation quotes it, section 4.3.1 reads “Center and balance areas of tile, if possible”, and section 4.3.2 reads “Usually, no cuts smaller than half size should be made. Make all cuts on the outer edges of the field.” The Tile Association in Britain gives its members the same advice in plainer language: avoid small cuts, as they can be difficult and do not look professional.

Notice the hedges. “If possible.” “Usually.” The foundation that trains US installers admits that a room’s size and shape and the size of the tile can make it impossible to center the layout in all aspects. A rule of half a tile is a target, and a room with five walls and a hearth will not always let you hit it everywhere. What the standard demands is that you look first.

Looking first has a traditional form. The British guide tells a floor tiler to mark a chalk line down the centre of the room, parallel to the most suitable wall, and it adds that this is normally judged by viewing the room from the doorway. The tiles are then laid down that line and worked out towards the walls, which is where whatever is left over shows.

Professionals go further and grid the whole floor in chalk before setting anything, so that every tile has a marked place. The point, in the foundation’s words, is that you can calculate the exact size of every cut in the installation before you start. A layout drawn to scale does the same job without the chalk, and it lets you try three starting points in the time it takes to snap one line.

One room, two honest answers

Take a floor 3 m by 2 m and square tiles of 300 mm, laid in a straight grid with tight joints. The area is 6 square metres and each tile covers 0.09, so arithmetic says 66.7 tiles, call it 67. No layout of that room uses 67 tiles.

Put a joint on both center lines. Ten tiles fit the 3 m exactly, so there are no cuts at the short walls. Across the 2 m, six full rows take 1.8 m and leave 100 mm at each long wall. The count is 60 full, 20 cut, 80 tiles in all, and every one of the 20 cuts is a strip 300 by 100 mm: a third of a tile, well under the half the standard asks for.

Now put a tile on the center lines instead, which moves the whole pattern by half a tile each way. The room takes 45 full tiles and 32 cuts, 77 in all. There are more cuts, on all four walls, but the narrowest is 150 mm, exactly half a tile, and the four corner pieces are 250 by 150. Moving the start by half a tile is all it took to turn a third of a tile at the long walls into a half.

You can reproduce both in the planner above: millimeters, a rectangle 3000 by 2000, a 300 by 300 tile, joint 0, the straight pattern, start at the center, then switch between Joint and Tile. The second layout needs three fewer tiles and has twelve more cuts. Which is better is a judgment about labor and looks, and it is yours. What matters is that the choice is visible before the floor is.

The joint is part of the tile

Tiles are sold by a nominal size, and the standards measure joints against the actual one. ANSI requires the joint to be at least three times the actual variation in the facial dimensions of the tile supplied, and never less than 1/16 inch. The standard’s own example, as the foundation quotes it, is a tile that varies by 1/16 inch, which needs a joint of at least 3/16 inch. The joint is where the differences between one tile and the next are taken up. In Britain, BS 5385-3 as summarized by The Tile Association gives 3 mm as the least width for a floor joint.

Those few millimeters accumulate. Each tile occupies its own size plus one joint, and a layout is a lattice of those modules, not of bare tiles. Give the 3 m by 2 m room a 3 mm joint and keep a joint on the center lines. The module is now 303 mm, the tenth tile no longer fits across the 3 m, and the count changes from 60 full and 20 cut to 48 full and 32 cut. The total is still 80, but twelve tiles that were whole now meet the saw, and the strips at the long walls shrink to 89.5 mm.

That is why a count taken from area, or from a sketch without joints, drifts on a real floor. It is also why the planner asks for the joint and for a measured tile, and why its sizes are offered by dimension only.

Two joints are deliberately left out of its grout total. The foundation’s trainers keep a movement joint of 1/4 inch around the perimeter, covered afterwards by a shoe mold or quarter round, and The Tile Association gives 6 mm as the British minimum for one. That gap is filled with something flexible, not grout, so the length reported is the joints between tiles only.

What a pattern costs

Patterns are sold as looks, but each one is also a way of meeting the walls. Only three regular shapes tile a plane on their own: the triangle, the square and the hexagon. Everything else on a tile showroom wall is a rectangle arranged in a lattice. Herringbone is the old one, an arrangement of rectangles named for the bones of a fish, usually cut 2:1 and sometimes 3:1, though the ratio need not be even.

Consider an L-shaped room 14 by 11 feet with a 5 by 4 foot corner taken out, 134 square feet, and a 6 by 24 inch plank with a 1/8 inch joint. Each plank covers one square foot, so area says 134. Laid out and counted with one whole tile for every cut piece, a straight grid needs 152, a half-offset brick bond 156, herringbone square to the walls 158, and the same plank on the diagonal 175. So the honest range for that room is 152 to 175 tiles, and nothing in the area figure hints at it.

The reason is the cut share. In the straight grid 37 percent of the tiles in that room are cut; on the diagonal it is 47 percent, because every tile that meets a wall meets it at an angle. Diagonal layouts also produce the smallest pieces: little triangles in the corners.

Offset patterns bring a constraint that has nothing to do with counting. Long tiles are rarely perfectly flat, and a half offset puts the high middle of one tile beside the low end of the next. The trade calls the resulting step between neighboring edges lippage. ANSI A108.02 therefore limits the offset to a maximum of 33 percent wherever the side being offset is longer than 15 inches, unless the tile’s manufacturer says otherwise.

That rule collides with the others. The foundation points out that with a third offset it becomes hard to keep every cut above half a tile and keep the cuts equal on both sides, and that the owner should approve the compromise. A third-offset layout is worth drawing for exactly that reason.

Buying, and what a plan cannot know

The count from a layout is conservative when each cut piece is charged a whole tile. A setter who gets two wall pieces from one tile will have tiles left over. That is the right direction to err in.

How much to add on top is less settled than the internet suggests. None of the trade body pages consulted for this essay gives a percentage. The planner offers a button for 10 percent as a round figure of its own, with no standard behind it, and leaves the field empty until you press it or type a number.

A plan has limits, and they are worth saying plainly. It assumes walls that are straight and corners that are where you measured them, and real rooms have neither. It treats every tile as exactly the size you typed, when the foundation puts the size tolerance for calibrated porcelain tile at just over 5/32 inch. It measures a notched piece by its overall width, so a thin leg around a door casing can escape the sliver warning. It knows nothing about the substrate, the adhesive or movement joints across a large floor.

Historic tile floors were laid by people who understood this. The US National Park Service’s guide to preserving them remarks that the modularity of tile, as standardized units, is what made it easy to fit into different sized spaces. Modularity is still the whole game. Print the plan, carry it into the room, measure from the two walls it names to the starting point, and snap that line first. Then check the first dry row against the drawing before anything is stuck down.