While both cob and daub are traditional, earth-based building materials composed primarily of mud and straw, their fundamental difference lies in their application and structural role within construction. Cob forms solid, freestanding, load-bearing walls, whereas daub is typically used as a filler material within the framework of a timber-framed building.
These ancient techniques represent distinct approaches to natural building, each with unique characteristics and historical applications.
Understanding Cob Construction
Cob is a monolithic building material created by mixing subsoil (which contains clay, sand, and aggregates), water, and a fibrous binder, most commonly straw. This mixture is then hand-sculpted or laid in courses to form thick, solid walls.
- Structural Role: Cob walls are inherently load-bearing. They are designed to be self-supporting and form the primary structural element of the building.
- Thickness and Form: Cob walls are typically very robust, often two or three feet thick. This substantial thickness contributes to their excellent thermal mass, which helps regulate indoor temperatures, keeping interiors cool in summer and warm in winter. Cob allows for organic, sculpted forms, leading to buildings with soft, rounded aesthetics.
- Durability: When properly maintained, cob structures are incredibly durable, fire-resistant, and even earthquake-resistant.
- Application Method: Cob is traditionally applied by hand in successive layers, allowing each layer to firm up before the next is added, a process often referred to as "building up."
For more details on the history and benefits of earth construction, explore resources on sustainable architecture.
Understanding Daub (in Wattle and Daub)
Daub, when discussed in traditional building contexts, almost always refers to its use in "wattle and daub" construction. In this system, daub is a plaster-like material applied over a woven lattice framework called "wattle." The daub mixture usually consists of clay, sand, water, and various binders such as straw, animal dung, or lime.
- Structural Role: Unlike cob, wattle and daub panels are not freestanding or load-bearing. Instead, they are specifically designed to fill the gaps within the structure of a timber-framed building. The timber frame provides the main structural integrity, while the wattle and daub serves as infill, insulation, and cladding.
- Thickness and Form: Wattle and daub panels are significantly thinner than cob walls, conforming to the depth of the timber frame. The "wattle" component is typically made from interwoven wooden laths or branches.
- Flexibility: This method allows for a more lightweight construction compared to solid cob and was historically popular in areas with abundant timber resources.
- Application Method: The daub mixture is pressed onto both sides of the woven wattle, creating a relatively solid panel that is breathable and provides a degree of insulation.
Key Differences at a Glance
The table below summarizes the core distinctions between cob and daub, highlighting their different applications and characteristics.
| Feature | Cob | Daub (in Wattle and Daub) |
|---|---|---|
| Primary Use | Freestanding, load-bearing walls | Infill panels within timber-framed structures |
| Structural Role | Main structural component of the building | Non-load-bearing, provides enclosure and insulation |
| Typical Thickness | Often 2-3 feet (very thick and monolithic) | Thinner, conforms to timber frame (typically 4-6 inches) |
| Construction Style | Sculpted, solid mass construction | Applied to a woven lattice (wattle) within a frame |
| Thermal Mass | High (excellent temperature regulation) | Moderate (primarily infill, not mass) |
| Aesthetics | Organic, rounded, substantial | Flat, often covered by plaster, defines framed sections |
In essence, while both materials share a similar humble composition, cob is the heavyweight, providing the very bones of a structure, whereas daub is the versatile filler, completing the skin of a timber-framed edifice.
