Herringbone Klombratorf Sod Block Cutting & Stacking in Turf Houses

The structural feasibility of building a two-meter-high, multi-ton wall out of soil depends on the tensile reinforcement provided by living botany. Icelandic turf masons recognized that dry hillside topsoil lacked cohesive strength; under compressive load, dry soil fractures and washes away during autumn rains. Consequently, turf was harvested exclusively from saturated wetland bogs (mýri).

These bogs are populated by specialized wetland monocots, primarily common sedge (Carex nigra), bottle sedge (Carex rostrata), and cotton grass (Eriophorum). These species develop extensive horizontal networks of tough, lignin-rich root rhizomes that do not decompose in anaerobic, waterlogged peat. When sliced into blocks, these root fibers act as millions of natural micro-tensile reinforcing fibers (analogous to steel fibers in modern shotcrete), giving the sod block extraordinary shear strength and toughness.

Extracting uniform sod blocks from waterlogged bogs required specialized iron tools developed specifically for the craft. The initial cuts were executed with the torfljár—a massive, crescent-shaped scythe blade mounted to a long wooden shaft with a cross-handle. Standing upright, the cutter pushed the blade vertically into the bog, slicing clean, straight lines through dense root mats that would blunt ordinary axes.

Once the grid was sliced, the craftsman deployed the torfspaði (turf spade). Unlike an ordinary garden spade, the torfspaði featured a wide, heart-shaped blade set at a pronounced forward angle to its socket. Driving the spade beneath the sliced sward, the artisan undercut the block at an angle, carving out the distinctive wedge-shaped profile of the klombratorf with its thick exterior face and long, tapered root tail.

The pinnacle of Icelandic sod building is the fiskibein (herringbone) bond. In this technique, klombratorf blocks are not laid flat like conventional building bricks. Instead, they are tilted on edge at an angle of approximately 45 degrees, with their thick grass heads facing outward and their tapered root tails extending into the interior wall cavity.

The orientation of the blocks alternates with each course: Course 1 slants to the right, Course 2 slants to the left, creating a continuous chevron pattern across the elevation. Crucially, each course of angled klombratorf is capped by a long, continuous horizontal strip of surface turf known as a strengur. The strengur acts as a tensile tie-beam that locks the tops of the angled blocks, distributing vertical loads across the entire wall length and preventing individual blocks from settling out of alignment.

The functional rationale of the herringbone bond is fundamentally hydraulic. In the stormy North Atlantic climate, horizontal seams in sod masonry trap wind-driven rain, allowing moisture to saturate the core and transform the wall into heavy, slumping mud. In herringbone masonry, the 45° angled block seams act as internal drainage chutes, directing water downward and outward toward the exterior face.

Furthermore, masons never built turf walls plumb. The exterior face was given a pronounced inward batter (halla) of approximately 1:5 (stepping back 20 cm for every meter of height). This inward slope resolves two mechanical challenges: it directs gravitational compressive loads inward toward the stable core, and it counteracts the lateral hydrostatic thrust exerted by the damp soil core during winter freeze-thaw cycles, ensuring the wall remains stable for generations.