What repairing our French farmhouse taught me about tiling

The typical roof-tile of southern France, and west and east of the Massif Central, is the semi-cylindrical tuile canal. 

In English it goes by a number of names: you may hear it called a monk-and-nun, mission, or barrel tile. 

From ancient times until a hundred years ago, these terracotta tiles were made from local clay, which was moulded on a log, or very often a person’s thigh, and then baked to make them water resistant. 

They are typically 45-50cm long and taper from 22cm at the broader end to 15cm.

An old roof made of such tiles is a thing of beauty, even if it is only covering a pigsty, and it is almost a miracle that it stays in place against all the storms thrown at it because there is not much holding it together. 

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Tiles form complex patterns

The ridge line will be made of a row of tiles fixed with lime mortar but beneath that the tiles are mostly laid loose, with their weight and friction as the only forces overcoming gravity to keep them in place. 

For this reason tuiles canal only suit roofs with a gentle pitch and are invariably found in regions of lower rainfall and no snow.

If they were laid on a steeply pitched roof they would quickly slide off. 

Two layers of tiles are needed, with tiles being used both ways around: concave beneath and convex above. 

In theory, at least, the rain has nowhere to get through and runs down the channels created by the concave tiles to fall away over the eaves.

Inevitably, a tuile canal roof will develop problems sooner or later. Storms and frosts work away at them. Tiles will slip out of place or else crack and even break altogether. 

Some of these problems can be anticipated and it is worth tackling them before they get worse.

Sky-high problems

If you need to sort out a roof, remember that it is quite a fragile structure. Use scaffolding to get up there and a roof ladder to distribute your weight. 

Walk with hobnailed boots on the tiles and you risk not only breaking them but losing your footing as they shift about.

At best, repairing such a roof involves shoving tiles that have migrated out of place back where they belong. You might even be able to do this with a long bamboo pole. 

At worst – short of replacing the entire roof – you are going to have to improvise repairs. 

It is worth keeping a stock of old tiles to slot in where a broken one has to be removed.

Where tiles are seriously slipping about you can sort them out with the judicious use of special roofing hooks (crochets).

If you do decide to replace a whole roof you might want to combine modern and ancient techniques. 

When stripping the old roof, keep as many of the unbroken tiles as possible. 

Ideally, fit a waterproof membrane but at least make sure the battens (liteaux) are in a good shape. 

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Use newly-bought tuiles canal à talon for the bottom row. 

These have feet to sit on the battens and holes to pass wires or hooks (crochets) through ensuring they will never go anywhere. On top of them you can then lay (convex side up) the antique tiles that you put aside during demolition. 

You can buy new, old-looking tuiles canal that come in variegated colours but to my mind they never look as convincing as the real thing. 

Either way, you will get the old-fashioned effect without the headaches of the old roof.