Common reed: from tradition to a sustainable future

Reed (Phragmites australis) is a perennial grass of the Poacee family. Spontaneous and cosmopolitan (it inhabits all continets except Antartica) it plays an important role of regulation of the ecosystem, with various actions carried out by all its components, from the rhizome to the tuft, and contributes to the biodiversity of the habitat.

Harvested and used as a building material since the Paleolithic, reed has been employed in every culture where it was avaible. Generally it was used for roofs, flooring and structural support in wood, bricks, stone or earth, held together with ropes.

Between the Tigris and the Euphrates

A particular case in which reed is used as a load-bearing structure is that developed by populations of marshy areas of southern and eastern Iraq, between the Tigris and Euphrates, known as Arab al-Ahwar, "marsh Arabs".

Their constructions exploit the natural flexibility of the reed under load, allowing them to be shaped into arches. The living space is realized by driving bundles of reed directly into the ground.

The thicker reeds are tied together to create curved columns, which are then joined to create consecutive arches that form the main frame. Bundles of thinner reeds positioned longitudinally between the arches, create the building's envelope.

The entire structure is then covered with woven mats, which thanks to their special textures, ensure ventilation and natural light.

This technique was adopted to building large public buildings known as mudhif, used to celebrate weddings and funerals, but also for private residences.

Casoni

The most significant reed buildings in Italy are the “casoni”, fishermen’s homes, mainly found in the Po Delta areas, in the lagoons of Veneto and Friuli and in Emilia Romagna.

The origins of casoni, of which numerous examples still exist, date back to the period between the Late Bronz era and Early Iron ages. Casoni have rectangular plans with only one space and gable roofs; the width and height are the same size, equal to double the length.

Wood load-bearing (local willow and poplar) is composed of vertical uprights, horizontal and diagonal beams, and a lattice to support the roof.

Reed. Bundles tied with natural fibers or, in recent times, with ropes or iron wires, were arranged in such a way as to create an effective external covering against bad weather, heat and cold and which allowed for breathability and the escape of smoke (in the older versions of the casoni there was no chimney).

By this use of the reed mat for human building activities, also the environment has benefited since the ancient times: seasonal harvest of reed promotes a more ordinate growth and avoid the accumulation of dead vegetation, which over time can cause the silting up of wetlands, the disappearance of this habitat and its biodiversity.

Things are there, navigating the light, emerging from the void to take place before our eyes. We are implicated in their appearance and disappearance, almost as if we were here for this very reason. The outside world needs us to observe it and tell its story, to have existence. [...]

In the marshes, the asphalt road winds along the water's edge, over a variegated surface of still, blackish patches. Long lines of black mud form embankments. And there are the eel ponds. Around them, a few very old, low houses, reed roofs, scattered trammel nets, and everywhere this muddy landscape under a sky tending toward gloomy. [...]

Gianni Celati

Towards the mouth

Common reed and biodiversity

Phragmites australis is a grass that can reach a height of 2–4 meters, and up to 6 meters in warmer climates. It has flexible stems with a diameter between 1 and 3 cm, deciduous blue-green leaves that are alternate and lance-shaped 1-5cm wide and up to 50cm long. The panicle-shaped inflorescence, about 40cm long, features feathery, brownish spikelets that bloom between August and November.

It grows in wet soils, freshwater or sightly brackish water, where, thanks to its knotted rhizomes, it plays a role in stabilizing shorelines. The plant also provides protection from wind, erosion, and sunlight, creating shaded areas that support the development of animal and plant species and bird nesting. In Italy, it is mainly found in the Po Delta area, along the Adriatic coast, and in the Maremma region.

Common reed also plays an important role in phytoremediation. The submerged part of the plant (stem and rhizome) host biofilms of organisms that retain pollutants and transform harmful substances such as nitrogen and phosphorus. The stems increase water turbulence, promoting sedimentation of pollutants. The leaves reduce water temperature, limiting the growth of algae.

In green building

Common reed is a material to be rediscovered, as it has unique and beneficial characteristics for healthy environments.

The part of the plant used in construction is the stem, rich in cellulose (35-50%), lignin (15-30%) and silica that make it rigid yet flexible and resistant to tension, fungal and bacterial attacks, and moisture. When the reeds hare harvested in winter season, without leaves, they contain a highly percentage of tannins that also increase resistance to pests and diseases.

The most common applications in contemporary green building are for roof layering and support, and thermal-acoustic insulation. Mats and panels made of reeds held together with galvanized wire or nylon thread (mechanically applied), also known as “arelle” or reed matting. These are used as a support for plasters layers, especially in combination with interior plasters realized with natural materials such as clay, lime or “cocciopesto”.

Restoration

Arelle are found in buildings dating back to the 15th century or later, in rural areas, where they were used as bases for false ceilings and vaults. Once plastered, these surfaces could be decorated with stucco or paintings: for this reason one of applications of reed mat in also in conservation and restoration.