terra-cotta-floor

The stultifying heat has finally let up, so yesterday afternoon I strapped on the kneepads and laid clay tiles on the terrace. It got me thinking about how much time I’ve spent on the floor in the last year.

Even at the beginning of this restoration project, when there was still so much to be decided, we knew we wanted terra cotta floors. The price seemed reasonable, the clay is quarried and fired locally, and they look fantastic – nothing would be more appropriate to the house. But the reality was much more complex and it involved a hell of a lot more time, expense, and stress than we imagined.

Admittedly, much of the struggle came from the fact that we were determined to do as much of the work ourselves as possible – a familiar attitude to anyone on a tight budget.

It all started with a square meter rate on our builder’s quotation: €22/m2 so if we did it ourselves we’d save over €5K. But the figure only told part of the story as it was just for laying the tiles. It didn’t cover buying, grouting, sanding, or treating them. Here’s a more complete picture of costs:

Job Rate Do it yourself?
Buy tiles €15 – €20/m2 no
Lay tiles €22 – €25/m2 yes
Grouting €10/m2 yes
Sanding €15/m2 maybe
Treating €5/m2 yes

So now we were looking at something more like €70/m2 although some of that can be saved by omitting or doing it yourself.

Laying the tiles was a big job, especially as we’d opted for a herringbone pattern – suddenly €25/m2 looked like a bargain. But we were very lucky in that we had expertise and a fantastic labour force in Martin, Sundried Steve, and Jason H. Even so, we managed less than 20m2 a day and it took 10 days to lay just two of the three floors.

To sand or not to sand? Terra cotta tiles are often irregular in all dimensions (even the machine made ones) which makes for an uneven surface. By grinding the grouted tiles with an industrial grinder, the floor becomes one smooth plane. In our case, even irregularities of around 4mm disappeared. You don’t have to do it, it just depends on the effect you’re going for: unsanded floors tend to look rough and rustic, sanded floors are uniform and more refined.

The advantages to sanding are that the finished floor is much easier to clean and you can be as sloppy as you like when grouting as any mess will be ground away by the sander.

On the downside, sanding is expensive. We intended to do it ourselves but couldn’t find anyone to rent us the equipment. It’s also a wet-grinding process and leaves a huge amount of water in the floor. This requires a long drying out period before you can apply most treatments, during which you can’t leave anything impermeable on the floor or the trapped water will discolour the surface of the tile in a perfect outline of whatever is covering it. You’d think that a principle as important as this would have been common knowledge among builders but surprisingly it wasn’t. It was a surprise we had to discover on our own.

Right, so now we’d laid, grouted, and sanded our beautiful floor, but it was still very porous. If you took a bucket of water and poured it on the tiles, in a few seconds it was gone. So imagine what happens when someone spills red wine or fries bacon in the kitchen: the floor would slurp it right up. Somehow the tiles had to be sealed.

Our first attempt at sealing was a water-based beeswax. It was fine but it only delayed water or oil soaking into the tiles and anything spilled left a stain unless wiped up immediately.

We could have used linseed oil but I had become precious about the colour of the tiles. We’d gone to a lot of trouble at the furnace choosing pallets of pale tiles: they’re a mix of beautiful light earthy shades – lots of pale yellow and pink and some green. Linseed oil makes the treated tiles significantly darker. In a sense linseed oil simply “pre-stains” the tiles – deliberately soaking them with oil, which then hardens and keeps other stuff out. Whatever stains then occur are also harder to see against a background of oil. I wasn’t keen.

So I ended up using a nasty petrochemical sealant that did a brilliant job without changing the colour of the tiles. Even an industrially-rated mask didn’t stop the fumes from addling my brain (though I found I was quite happy about it) and we had to send Henry out of town until the smell cleared.

I want to emphasise that the decision to use this sealant wasn’t taken lightly and is uncharacteristic of the restoration. We’ve used milk-based paint and earth pigments throughout the house to minimise VOCs and reduce the waste impact (up to 10 tonnes of toxic waste result from the manufacture of 1 tonne of typical interior house paint). The kitchen is FSC maple and finished with tung and linseed oil. We’ve used a natural woodworm repellent rather than insecticide on the beams. And then we go and put this crap on the floor. But it works, and works very well.

Even after the floor was laid, sanded, and sealed, the story wasn’t over. Because in the following months something interesting emerged: cracks from thermal expansion. In some cases these formed in exactly the right places, for example on the grout line in a doorway, but occasionally in the wrong places as well. As with so many aspects of terra cotta behaviour, no one here saw this coming or had a firm strategy on how to deal with it. Absolutely bizarre. I think I’m now the local expert on terra cotta floors, which is not a title I covet.

To deal with thermal expansion, next time I would leave a continuous gap ungrouted in strategic locations. These gaps could then be grouted with a weaker grouting mix. Or maybe the insides of the gap could be treated with a sealant to prevent the grout from gaining much “hold” on the tiles. Needs some experimentation. If you’ve got a strategy, let me know.

So on future projects will we use terra cotta? Maybe, as the end result is gorgeous and in this case it fits perfectly with the house. But I would look long and hard at manufactured tiles first and if there was a satisfactory alternative I would pounce.

disclaimer: every project is different and the information in this post relates to our experience only. Use it at your own risk.