The external cladding and parapet walls largely define the moderne/art deco style houses.
Internationally, concrete and steel were were well suited to the clean, uncluttered lines and minimal decoration that were inherent in the philosophy of the modernist style, and these materials were commonly used for residential construction.
Brick was also used occasionally. Concrete, though mainly used for multi-unit housing, was occasionally used for residential construction in New Zealand (see concrete construction for more).
The most frequently used external cladding for art deco houses was stucco plaster – a cement plaster typically consisting of a 3:1 sand:cement mix applied over galvanised wire netting or metal lath reinforcing that has been fixed over a rigid or a non-rigid backing. It was applied as a three-coat plaster to a thickness of approximately ¾” (19–20mm).
Rigid backing materials included asbestos-cement sheets, close-boarded timber sheathing (diagonal sarking), a pumice and cement-based sheet called konka board or, in the early days of its development, plasterboard (see Plasterboard). Non-rigid backing materials included heavyweight building paper or bitumen-impregnated felt.
Where a rigid backing was used, building paper was inserted between the backing and the framing. Where a non-rigid backing was used, the building paper or bituminous felt served both as the backing and the waterproof membrane.
If rigid backing boards were used, holes or ‘V’ cuts were made in the outside edges of the dwangs and plates to allow air to circulate through the timber framing that would otherwise be restricted by the closely fitted backing material.
The cement plaster was applied in three coats. The final plaster coat was applied as a smooth or a textured finish, often applied as a splash, typically radial or fan-shaped and sometimes trowelled to flatten the lumps. Not all houses were painted immediately, as the plaster of some was dyed a pastel colour. Painting for most of these came later when the plaster alone proved not to be weathertight.
Two-storey houses often have different textures to mark each floor.
Stucco had a tendency to crack as a result of poor mix quality and poor application, settlement of the foundations, or lateral movement caused by wind or earthquakes, resulting in water ingress into the wall framing.
Despite this, stucco cladding is an integral part of the housing style. Stucco is rarely replaced, but patching or remedial work may be needed.
Asbestos-cement sheet cladding
Asbestos-cement sheets had been available since the early 1900s. They were manufactured by combining asbestos fibre with cement to form thin, rigid sheets suitable for cladding and lining buildings. By the 1930s it was extensively used as a rigid backing board for stucco.
Early asbestos-cement sheet such as ‘Poilite’ was imported from England, and ‘Celotex’ and ‘Fibrolite’ were imported from Australia. ‘Walasco’ cement board was a New Zealand made product that had small square projections that were intended to improve the bonding of the stucco to the substrate.
Sheet widths were between 18” and 48” (450 to 1200 mm) and were generally 3/16” (5 mm) thick.
Konka board was a New Zealand invention, patented in 1915, that was used as a backing board for a stucco plaster finish.
It was a lightweight, cement-based panel system using volcanic pumice as an aggregate with a backing of building paper. Panels were about 36” x 30” (900 x 760 mm) and 5/8” (15 mm) thick.
Sheets were fixed onto timber framing in a staggered pattern using metal clips. The joints were covered with hessian (sacking) soaked in wet cement to provide good key for the plaster finish.
Another material that was also in use during the 1930s as a rigid backing board for stucco was plasterboard, which consisted of sheets of gypsum plaster covered with paper on both sides. The sheets were coated in bitumen before being fixed to the timber framing. Steel mesh covered the sheets and the whole surface was plastered. As its relative unsuitability as a stucco substrate was recognised, plasterboard was eventually recommended for internal use only.
Weatherboard cladding was sometimes used on art deco houses.
Weatherboards were bevel-back profiles typically from 5 x 1” (125 x 25 mm) timbers which, after seasoning and dressing, had finished dimensions of around 4½ x ¾” (114 x 20 mm). Weathergrooves were not commonly cut into the weatherboards.
The external corners were mitred joints that were initially filled with putty but, in later construction, were capped with copper soakers.
Weatherboards were sometimes fixed vertically on rounded corners.
Weatherboard houses may have had other claddings installed over the top.
External colour schemes were generally light and monochromatic. White was popular, but cream and pastel colours such as pink, pale green and beige were also used for both the exterior walls and window joinery. Doors were often painted a stronger colour, and the decorative details such as the bas-relief patterns were also picked out in darker colours.