Bağdadi Timber Lathing & Chunam Lime Infill Plasters in Safranbolu Konaks

In traditional Safranbolu residential architecture, building loads decrease progressively as one ascends from foundation to roof. While the ground floor is a fortress of solid stone masonry designed to resist dampness, stable fires, and slope slippage, the upper stories—particularly the cantilevered çıkma projections—demanded an ultra-lightweight enclosure system. If carpenters had infilled the extended cantilevers with heavy stone or solid fired bricks, the resulting eccentric dead load would have caused catastrophic joist sagging, joint rotation, and structural collapse during seismic shaking.

The solution was the bağdadi wall system—a hollow, composite timber lath-and-plaster curtain wall. Rather than bearing vertical gravity loads, which were carried entirely by the primary timber posts (direk) and diagonal braces (payanda), the bağdadi assembly functioned as a lightweight spatial divider and weather screen. By nailing narrow horizontal wooden laths across both the interior and exterior faces of the timber studs, carpenters created a hollow wall cavity measuring 10 to 14 centimeters in thickness. This air cavity functioned as a natural thermal insulator while drastically reducing structural dead weight to roughly one-fourth that of an equivalent masonry wall.

The integrity of a bağdadi wall begins with the quality and preparation of the wooden laths (bağdadi çıtası). Master craftsmen favored straight-grained sweet chestnut (Castanea sativa) or slow-growth Scots pine (Pinus sylvestris). Crucially, the best laths were split (rived) by hand with a froe and mallet along the natural wood grain rather than sawn with mechanical sawmills. Hand-split laths followed the continuous fiber alignment of the timber, resulting in strips that possessed superior tensile elasticity and would not snap or warp when wetted by wet plaster.

These laths—typically 20 to 30 millimeters wide and 5 to 8 millimeters thick—were nailed horizontally across the vertical studs using wrought-iron rosehead nails. Carpenters maintained a strict gap of 10 to 15 millimeters between adjacent slats. This spacing was critical: when the plasterer troweled the base coat onto the wall with firm compressive pressure, the wet, fibrous mortar was extruded through the gaps. On the back side of the lath, the extruded plaster slumped downward under gravity, forming continuous interlocking horizontal ridges known as mechanical keys or 'nibs'. Once cured, these hardened lime nibs anchored the plaster permanently to the wooden framework without requiring chemical glues or synthetic adhesives.

The mortar applied over bağdadi laths in Safranbolu is not simple gypsum or cement, but a sophisticated lime formulation known colloquially as chunam and horasan. The binder was produced by burning local pure limestone in wood-fired kilns and slaking the resulting quicklime in water pits for months—and often years—to yield an extraordinarily silky, plastic calcium hydroxide (fat lime) putty. Because pure fat lime cures solely by atmospheric carbonation (absorbing ambient CO₂), thick plaster coats could take months to harden in deep wall cavities.

To accelerate curing and impart moisture resistance, Ottoman artisans incorporated horasan—a reactive artificial pozzolana made by crushing low-fired clay roof tiles, bricks, and ceramic pottery into fine powder. The amorphous silica and alumina in the baked clay reacted with the slaked lime in the presence of water to form crystalline calcium silicate hydrates (C-S-H), creating an indigenous hydraulic mortar that hardened reliably throughout the entire thickness of the coat. Furthermore, generous quantities of washed and carded goat hair or cow hair were kneaded into the scratch coat (kaba sıva). These resilient animal fibers acted as microscopic tensile reinforcement, bridging across drying microcracks and preventing the plaster from dislodging under building vibration.

From a building physics perspective, the bağdadi wall is a masterclass in dynamic hygrothermal equilibrium. In northern Anatolia's climate—where damp Black Sea winters alternate with dry, hot summers—interior timber framing must remain dry to avoid fungal decay and wood-boring beetle infestations. Because slaked lime plaster is entirely vapor-permeable (Class I vapor open), any humidity generated inside the household from cooking or breathing passes effortlessly through the plaster matrix and diffuses into the ventilated hollow wall cavity, escaping through eaves vents.

In historic conservation practice, the greatest threat to bağdadi assemblies is the misapplication of modern synthetic materials. During post-war renovations, many historic konaks were coated with impermeable cement stuccos and acrylic exterior paints in an attempt to modernize facades. These impermeable skins trapped condensation inside the wall cavities, rotting the chestnut laths and timber posts within decades. Authentic restoration requires the painstaking mechanical removal of cement layers, the replacement of rotted laths using authentic split chestnut strips, and the reapplication of multi-coat slaked lime plasters finished with pure slaked lime whitewash (kireç badana).