Ceramic Tiles for Walls and Floors

I have not done a lot of ceramic tile laying or setting. I've only done work on my own houses, for myself. Certainly I am not an expert tiler, but I have worked with many excellent ceramic tilers over my years as a builder, so here are some of my thoughts on tiles and tiling.

A portion of mosaic wall tiling, depicting the Empress Theodora in the 1400 years old Basilica of San Vitale in Ravenna. Image thanks to Wikipedia.

Introduction

Ceramic tiles have been around for centuries. They are capable of providing extremely durable hard wearing surfaces from warehouse floors to space shuttle exteriors.

Tiles have long been a medium of artistic expression. It would be very hard to remain unmoved, when viewing the complex geometric patterns of the ceramic tiles of the Alhambra in Spain, or the Byzantine mosaics in the churches of the Italian city of Ravenna

Ceramic tiles - Hand made wall tiles, Alhambra Palace in Granada, Spain. Image thanks to Wikipedia.

Above is a photo of just some of the highly complex geometric patterns in the ceramic tiles covering the walls, ceilings and floors of the Alhambra Palace in Granada, Spain. Built by the moors in the 13th century.

I have a good friend who has told me (more than once after a few beers), that he well remembers going to an archaeological dig in southern England when he was a boy. They were unearthing the floor of a 2000 year old Roman villa, and fifty or more years later he can still remember his amazement at how fresh and perfect those floor mosaics were.

There is a temple in Bangkok, Wat Arun (Temple of the dawn) that under certain light conditions glows with a strange and beautiful light. When you approach it you begin to see that the whole surface of the external stucco has had embedded into it hundreds of thousands of pottery shards. Parts of rice bowls, tea cups, plates and dishes of many different colours arranged in patterns. The builders could not afford the cost of purpose made ceramic tiles, and so the people donated their pottery.

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Tile Manufacture

When I was a kid, my dad was a keen amateur potter. We made our own ceramic tiles.   He bought bags of powdered clay and mixed it with water until it became malleable.   Then he would thump a two or three kilo lump down onto his bench, cut it in half with a wire, bash it together again in a different position and repeat the process.  Again and again, Thump,cut,bash.

This process of thoroughly mixing the clay and removing all the air bubbles was known as wedging.  I have done my share of it I'll tell you, Thumping,cutting,and bashing. A basic machine that took over wedging by hand is the pug mill.

He then rolled the clay with a rolling pin on a sheet of glass (a flat surface), cut it into shapes and left it to dry.   Later the tiles would be painted with a slurry of water and a powdered glaze.   After more drying and more painting they were loaded into a small electric kiln and fired at the appropriate temperature for the type of tile and glaze.

We got a few pleasant and happy results, but the vast majority of our ceramic tiles had some or many defects.   They could bend, twist, crack, stick together with runny glaze, the glaze might run off completely, if we opened to kiln too soon the glaze would craze, (crack all over).   We made some truly terrible tiles.  It was all good fun though and I I still have a regard for hand made pottery. Knowing how hard a thing is to do, increases the admiration and respect for the people who do it well.

So at the most basic level that is how ceramic tiles are made.  I wouldn't begin to guess the complexities of a modern ceramic tile plant, with the differences between wet pressed tiles, dry pressed tiles, extruded tiles or the many types of continuous kilns.

Tiles Used Around the Home

There are so many variations on the theme, I doubt if anyone has a full list, but here is my shot at it, with a few comments.

• Floor ceramic tiles are usually thicker that wall tiles, say 8mm to 12mm with a very hard wearing surface. They come in all shapes and sizes with a trend I think to going larger. It was common to see floors done with 150 square tile, but now they are all larger. It is common to see the same tile cut and used as skirting tiles. Floor tiles almost always have a texture to the surface glaze as an anti-skip measure. It is always a trade off against grip (especially when wet) and ease of cleaning.
• Wall tiles are almost always confined to wet areas in residential construction, bathrooms, toilets and laundries. They are also used for splash backs to kitchen benches and sinks etc. They are invariably thinner and softer than ceramic floor tiles. Quite often they used to have rounded bullnose corners but that is rarely seen now. Also not seen much are the dimples at the edges that were there to help keep a consistent width joint.
• Mosaic floor tiles are groups of smaller tiles laid in sheets, say 300 x 300, onto a mesh backing, to hold them in place while being laid. They were used a lot in bathrooms and shower areas, were there falls to the floor. They were easy to lay on falls and curves, because of the small size of each individual tile, but they have gone out of fashion.
• Quarry tiles, for floors, are either unglazed or very lightly salt glazed, giving them their typical earthy colours. Quite thick they are more often used outside on patios.
• Slate tiles are obviously not ceramic at all, they are made out of natural slate that is split and cut to sizes. I have only ever done one job with slate and it was against my advice, that the lady of the house went ahead with a large bathroom, with slate wall and floor.  I was sure it would look too dark, but in the end it looked stunning. What helped was the fact that we put a skylight in the roof and ceiling, and she had naturally growing pot plants around.  Slate is not recommended for bathrooms, but with a few coats of sealer, that is kept well maintained it is OK. Typically the grout joints are wider than standard tiles because of the irregularity of the slate pieces.
• Italian Monocottura tiles are typically large strong and expensive.   At a guess the Italian manufactures were the first to create large yet strong tiles that resist cracking in use.  Spanish manufacturer's followed with the similar Monoporosa tiles.
• There are a range of ceramic tiles that look like a man made granite in various shades. They have a semi gloss face and the whole thickness of the tile is the same, no separate glaze to the face, so cut edges can be ground and polished if needed. Any small chips to the edges are hard to see. Again these are very strong hard tiles.
• Nosing tiles are purpose made with curved edges and anti slip grooves in them, used for the edge of steps and stairs.  They are thicker than normal and being extremely hard wearing, they are hard to cut. Usually a diamond blade is used.
• Volcanic rock, lava rock are cut slabs of naturally occurring rock, quarried from volcanic slopes in Indonesia.  like slate is not ceramic at all, but I have seen it used to good effect in outdoor areas.   Like slate it needs sealing to keep it's good looks.

Setting Out Ceramic Tiles

Here are a few guideline for setting out a tile job.   I say guidelines and not rules, because every job is different, and a rule that works in one place may look silly in another.

Always try to keep cut tiles at least a half tile or greater. The reason for this is that it just looks better. Also small differences the walls are not seen.  A wall that is 5mm out of plumb or out of square will not be obvious when a 140mm cut tile abuts it, but if the cut tile row is 20mm to 15mm, then the eye will be able to pick this.

Ceramic tiles - Setting out

In the sketch on the right, the grey are is to be tiled.  Lets say it is a bathroom wall.

I mark a center line on the wall and pencil in a row of tiles (top row).   Straight away I can see that I will have a small cut tile at each end.   So I start again, this time with the first tile half way on the center line.  This looks far better.  Note that by doing it this way, I still only use the same number of tiles.

So to start tiling that wall I would find the center of the wall, and half a tile left or right of it I would make a vertical line the full height of the proposed tiles.  This line is my starting line.  I wouldn't start at the side.  By starting at the middle I minimise any creep or discrepancy that may build up as I go along.

Ceramic tiles - A house floor plan

In the house floor plan that I have sketched out above

• The longest run of tiles is going to be in the corridor, That is one that I would want to look good.
• I set up a center line there, parallel to the wall.
• The next longest run is across the living and dining rooms, so I set out another line parallel to the end wall and say centered in the dining room.
• Then comes a very important part, check the two lines for being square, or at right angles to each other.
• You may use a steel square or to be more accurate, use a 3,4,5 set out.
• Any triangle that has sides sides in the ratio of 3,4 and 5 always has a true right angle at the corner opposite the 5 side.
• So in this case I might use 3m x 4m x 5m, whatever fits in as long as the ratio is 3,4,5.

I would most probably find that the two line are square.  If not I would adjust one or even both of them to get a square set out.  The tiles will be laid out on a square grid so I have to start off right, and I also at this stage need to know if the walls are running out of square in any way.

• I would then from the center lines mark out the position of the tiles each way.
• I may even in a complex area like this one lay a few loose tiles on the floor to see the position at a glance.
• Now comes the decision process.  Trying to keep every wall joint looking good is not easy, and will usually take adjustments either way.
• The main thing I try to do is make the first view that a person gets on entering the house the best.
• At this stage quite often a tiler would call me over and ask for my opinion, should we make the corridor perfect at the expense of a small cut in front of one of the double doors, or should we nudge them over a touch?
• There is rarely a full house job that is good at every wall, that's why I think it is good to have a second opinion.
• If one wall is a touch out of square, I give that one a wider cut if possible, at the expense of the opposite one that is parallel to the run of tiles.
• I take into account that that there may be furniture or cupboards against a wall.
• If the floor area is concrete and quite large,* it will probably have construction / expansion joints in it. Arrange you tile expansion joints over them. More on expansion joints below.

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Out Of Square Setout

What to do if a wall or walls are out of square.
I did a job where we built right up to a boundary line, and in a 6m run that end wall was about 300 out of square with the rest of the house.  We used 200 x 200 tiles on a normal square pattern and at that wall the tiles were all cut on an angle. The rest of the walls were OK and the tiles were parallel to them.  You could see the angle on the walls and on the ceiling as well as the floor.  The job looked quite good and and it was just accepted that the wall in question was out of square.

Ceramic tiles - Diagonal set out masks wall that are out of square.

More difficult are the ones that are not obvious, only the tile pattern will show up any discrepancies in the wall layout.  An option is a diagonal set out.

In the sketch above, I have made the bottom wall out of square with the rest and the two middle/corridor walls offset from each other.  The 45 degree pattern lessens the impact of any irregularities.  To do a floor like this, there is more work involved and more tile wastage.

I have seen diagonal floors like this, combined with a border tile that runs parallel with the walls that look very effective.

If you are an owner builder and starting from the ground up, the old saying "measure twice and cut once" is always good to bear in mind.  A small mistake in the foundations can be hidden for ages, the formworkers and concreters have been paid and long gone.   Then at the end of the job the tiler picks it.  Check your setting out!

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When to Lay Tiles On A New Concrete Slab

Easy answer, leave it as long as you can.  The longer the better.

It is ironic that we spend the first four weeks or longer trying to cure the concrete, that is slow down the drying process, by keeping it wet etc.  Then we have to wait for it to dry out before we can tile.

Concrete when it is first poured, shrinks as it dries out.  This is a process that is fairly rapid to start off, most of it happens in the first few hours, then the process slows down gradually.

In the normal construction period of a house, the floor tiles are laid when most of the house is finished, many times this may be over 12 weeks after the slab has been poured.  The slab has to be fully cured and dry before tiles are laid, and in part this depends on the thickness of the slab.  An average house slab is say 100mm (4") thick.  I would never lay tiles on a slab this thick in less than 8 weeks.

I have heard a rule of thumb saying one month drying time for each inch of thickness in the slab.

So if you have a small addition that went up really quickly, hold off on laying the tiles.  One trick that I always do on new jobs, is to tape a small piece of plastic to the concrete, and if after a day or so small beads of moisture show up underneath, then the concrete is still actively drying out and I leave it a week or so and try again.

The BCA states that all concrete floors on the ground, used for a habitable space should have an approved waterproof membrane under the concrete.  This is to stop dampness coming up through the concrete.  I have seen floor tiles separating from damp floors like this, and after being relaid, those coming up again.  Typically a room is later made on a slab that was never intended for a habitable room.  I you want to tile a slab that you are not sure of, then take advice from a good quality tile shop, there are membrane/underlay/isolation type products that will allow you to do this.

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Expansion Joints-Movement Joints-Control Joints

Most materials used in home building move over time.   This can be due to thermal movement or other causes.  Ceramic tiles are no exception, so knowing this, in order to stop unsightly cracks we allow for any movement by using expansion joints. Put expansion joints at the following locations:-

• Around the edges of a floor, leave a clear 5mm gap. By clear I mean definitely no grout, but also don't let adhesive well up between the tile and the wall.
• Quite often a skirting goes over the gap, so no other work is needed, unless it is a ceramic tile skirting.  In this case fill the gap with flexible sealer like "Caulk and Colours"
• On large floors provide a joint about every 5m or so.  That is, say a minimum 4mm joint using flexible sealer.
• If the concrete floor has an existing expansion joint in it, put an expansion joint in the tiles, over the concrete joint.
• If you have an irregular and quite large crack (bigger than an average shrinkage crack) consider putting an expansion joint either side of it and laying the tiles over the crack with flexible adhesive.
• Vertical junctions of walls.
• Junctions of walls and cabinets/bench tops.

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