Technique · Catalonia
Hearting: the part of the wall nobody sees and everybody depends on
Every visitor to a repair day looks at the face of the wall, because the face is where the craft shows. The first thing I was taught in Scotland, and the thing I most often have to explain in Catalonia, is that the face is only as good as whatever is packed behind it.
Laid 16 March 2025Checked again 10 August 20257 min on the hill
Lift 1 of 4
A lesson from a wet field in Galloway
The first dyke I ever worked on was a field wall about a metre and a half high that had fallen in a winter storm and lay across a sheep track in a long grey spill. The waller I carried for made me spend the whole of the first morning sorting the fallen stone into piles by size and doing nothing else. The biggest went for the foundation, the long ones for the throughs, the good-faced ones for the two faces, and everything smaller than a fist into a heap he called the hearting. By lunch the hearting heap was the biggest of all, and I remember being faintly insulted that it was my job.
What he wanted me to understand, and what took most of that summer to sink in, was that a double dyke is really two thin walls leaning on each other, and the hearting is what makes them lean on each other rather than fall away from each other. Each face stone is set with its length running into the wall and a slight fall towards the outside so that rain runs off. Behind it there is a gap between its tail and the tail of the stone on the other face, and that gap has to be filled solid, stone against stone, or the face stones will rock and eventually walk out of the wall.
Lift 2 of 4
Placed, not thrown
The single habit that separates a lasting wall from a short-lived one is how the hearting goes in. A beginner, and I was one, tends to lay a course of face stones and then tip a bucket of small stones into the middle and move on. It looks full. It is not, because tipped stones land at random, bridge across voids and leave pockets of air that settle over the following winters. Settling hearting lets the face stones drop at the tail, which tilts them outward, which is the start of a belly in the wall and, a few years later, a collapse.
Properly placed hearting is slow. Each piece is chosen to fit a particular gap behind a particular face stone, set by hand so that it wedges against the tail and cannot move, and the next piece is chosen to lock the first one. The hearting is brought up with every course, never left to catch up later, and the top of each course should be flat enough to take the next face stone without rocking. On a good day in Scotland I could build about a metre of dyke to full height, and roughly half the time went on hearting.
Lift 3 of 4
Reble on a Catalan terrace
The terrace walls in the hills west of Barcelona are not double walls. A marge, as the volunteers call a terrace wall, has one face, and behind it is the hillside itself, cut back and levelled so that vines, olives or almonds can be planted on the flat above. The equivalent of hearting is called reble, and on my first repair day I assumed it did the same job. It does part of the same job, and one other job that a Scottish field dyke never has to do.
The reble behind a terrace wall is a layer of broken stone between the back of the face stones and the earth of the hill. It supports the tails of the face stones exactly as hearting does. It also drains the terrace, because when heavy autumn rain soaks the soil above, the water has to go somewhere, and if it cannot pass freely through the wall it builds up pressure behind it and pushes it over. The older volunteers are strict about keeping earth out of the reble for this reason. A layer clogged with soil holds water like a sponge.
Lift 4 of 4
What I now do differently on both sides
Working on terraces has made me more careful with hearting at home, not less. On the few occasions I have been back in Scotland and helped on a wall, I have noticed how often dykes fail from water as well as from settling, especially where they cross a slope and the uphill side is permanently wet. The Catalan habit of treating the space behind the face as a drain as much as a filling seems to me good sense for any wall on a hillside.
In the other direction, I have brought the placed-not-thrown habit to the reble, and on the last three repair days the section leader has let me work the back of the wall rather than the face, which I take as a compliment. The reble there is usually thrown by the bucket, because the terraces are long and the volunteers are few and the older walls built that way have mostly stood. My own sections go more slowly. Whether they stand longer, the next thirty autumns will decide, and I will not be the one writing that entry.
Measurements in this note were taken with a folding rule and a level on the day and copied up the same evening. It is a hobbyist's record, not a specification, and any wall that holds up a path or a field deserves a proper builder.