Construction practices#
Australia#
According to statistics from NEXIS (2020), the distribution of wall materials used in residential construction is shown in the table below.
STATE |
AAC |
CAVITY SOLID MASONRY |
FIBRE CEMENT |
METAL SHEETING |
MUDBRICK OR RAMMED EARTH |
PRECAST CONCRETE |
REINFORCED CONC MASONRY |
SYNTHETIC |
TIMBER |
VENEER MASONRY |
|---|---|---|---|---|---|---|---|---|---|---|
ACT |
0.00% |
95.60% |
4.10% |
0.30% |
0.00% |
0.00% |
0.00% |
0.00% |
0.00% |
0.00% |
NSW |
0.00% |
17.30% |
7.20% |
1.10% |
0.00% |
0.40% |
0.40% |
0.00% |
15.30% |
58.20% |
NT |
0.00% |
28.20% |
16.60% |
5.30% |
0.00% |
0.00% |
9.20% |
0.00% |
34.20% |
6.60% |
OT |
0.00% |
12.00% |
11.80% |
2.40% |
0.20% |
0.00% |
2.50% |
0.00% |
34.90% |
36.00% |
QLD |
0.00% |
42.80% |
7.40% |
2.10% |
0.00% |
0.00% |
2.30% |
0.00% |
31.20% |
14.30% |
SA |
0.00% |
89.60% |
8.80% |
1.00% |
0.00% |
0.00% |
0.10% |
0.00% |
0.00% |
0.40% |
TAS |
0.10% |
12.30% |
9.70% |
3.20% |
0.20% |
0.00% |
0.40% |
0.30% |
25.80% |
47.90% |
VIC |
0.10% |
16.60% |
6.70% |
1.70% |
0.10% |
0.00% |
0.30% |
0.10% |
24.00% |
50.40% |
WA |
0.00% |
82.60% |
6.80% |
1.80% |
0.10% |
0.10% |
0.00% |
0.00% |
3.10% |
5.50% |
NATIONAL |
0.00% |
37.00% |
7.30% |
1.60% |
0.10% |
0.10% |
0.80% |
0.10% |
18.40% |
34.70% |
Residential buildings in Australia are primarily separate houses (89.5%), typically of masonry or timber construction.
New Zealand#
The documentation that supports the model, shared by GNS Science, describes the most common structure types in New Zealand:
Reinforced Concrete, Shear-Wall: Buildings constructed of reinforced-concrete shear walls, floor slabs and roof slabs. Shear-wall buildings typically include columns to carry gravity loads, usually in the interior for low-rise buildings, and on the exterior for medium- and high-rise. Gravity loads are carried by the shear walls and columns, and lateral earthquake forces are resisted by the shear walls. Most medium- and high-rise commercial buildings are of this type, which is common throughout New Zealand.
Reinforced Concrete, Moment-Resisting Frame: Buildings having reinforced concrete columns, beams, floor slabs and roof slabs. The components are often cast-in-place. Gravity loads are carried by the columns, and lateral earthquake forces are resisted by the rigid moment-resisting frame that is created at the intersections of the beams and columns. Design for seismic resistance was introduced in the 1940s, but pre-1970 methodologies are now regarded as inadequate. Not common in New Zealand, except for 1 or 2-storey shops which are very common. Such a shop typically has shear-wall sides (often for fire-resistance) between it and its neighbours, sometimes a shear-wall rear, but the front, usually with large openings, relies on a moment-frame for earthquake resistance. They are placed in this class because the moment-frame front is expected to govern the minimum seismic resistance.
Steel, Braced Frame: Buildings having steel columns and beams that are braced, either concentrically, eccentrically, cross or K. Floor and roof diaphragms may be cast-in-place reinforced-concrete slabs, or pre-cast (e.g. hollowcore) reinforced-concrete slabs. Exterior walls can be any of several types such as metal, precast concrete panel, or brick masonry. Gravity load are carried by the columns, and lateral earthquake forces are resisted by the steel bracing. This type of construction is not common in New Zealand, and is mostly low-rise or medium-rise.
Steel, Moment-Resisting Frame: Buildings having steel columns and beams that make up a rigid moment-resisting frame system. Floor and roof diaphragms may be cast-in-place reinforced-concrete slabs, or pre-cast (hollowcore) reinforced-concrete slabs. Exterior walls can be any of several types such as metal, precast concrete panel, or brick masonry. Gravity load are carried by the columns, and lateral earthquake forces are resisted by the steel frame. This type of construction is not common in New Zealand, and is mostly low-rise.
Light Timber: Buildings with walls constructed of 100x50 mm wood or sheet-steel studs spaced at 600 mm covered on the outside with a variety of cladding materials. Starting with the most common the external cladding materials are timber weatherboards, brick veneer, stucco or corrugated iron. Interior cladding is nearly always gypsum board. Floors may be timber or reinforced-concrete slab. The roof framing is usually timber, and the cladding may be a variety of materials including corrugated iron, clay tiles, concrete tiles, or pressed sheet metal tiles. Gravity loads are carried by the walls in compression and lateral earthquake forces are resisted by the walls in shear. This is by far the most common form of residential construction in New Zealand, and also is common for low-rise non-residential buildings. Well constructed buildings of this type are typically highly resistant to collapse because of the toughness of the walls and the light weight of the superstructure.
Concrete Masonry: Buildings having walls constructed of hollow concrete masonry blocks in cement mortar. The hollow masonry blocks are reinforced by inserting reinforcing steel in the cells and then filling the cells with grout. Floors are typically reinforced concrete. The roof framing is usually timber or steel, and the cladding is usually corrugated iron. Gravity loads are carried by the walls in compression, and lateral earthquake forces are resisted by shear in the walls.
Reinforced Concrete (Tilt-Up): Buildings having perimeter walls made of large single-height reinforced-concrete panels that are tilted up into wall position. The wall units are then anchored to the foundation and are inter-connected. The floor is reinforced concrete, and the roof system may be steel or timber truss, or steel portal frame. Roof cladding is usually corrugated iron. If the building has a large foot print there may be intermediate columns between the walls to support interior gravity loads. Gravity loads are resisted by the tilt-up walls and any intermediate columns. Lateral earthquake loads are resisted by the shear-wall action of the tilt-up walls, and portal frames if present. Tilt-up buildings are typically one story. Tilt-up buildings are most commonly used for industrial and commercial occupancies.
Light Industrial: A type of construction that is common in New Zealand for industrial occupancies. Typically long narrow single-story buildings, having no interior columns, that are on reinforced concrete floors. The framing typically consists of portal frames (either steel or laminated timber) in the transverse (short) building direction, with diagonal tie rods in the longitudinal (long) building direction. The wall and roof claddings are typically corrugated iron, fibreglass, or asbestos. Sometimes the lower parts of the walls may be of reinforced masonry or concrete. Gravity loads are carried by the columns of the framing, and lateral earthquake forces are resisted by moment-resisting frame action in the transverse direction and by the diagonal tie-rods in the longitudinal direction. Low-rise only.
Advanced Design: Buildings in which special devices are used to minimise the seismic response. Current techniques include “seismic-isolation”, in which a layer of yielding devices limits the transmission of shear forces into the building (damping is often provided within the devices, e.g. lead-rubber bearings, RoGliders), “additional damping”, provided by devices like lead-extrusion dampers or sliding (friction) steel joints that absorb seismic energy and so reduce the building’s response, or “stepping” mechanisms. Isolation devices may be used in new construction or as retrofit to existing, typically heritage, buildings.
Brick Masonry: Buildings having walls constructed of solid clay bricks in cement mortar. There is no reinforcement. Floors are typically wood joists covered with boards. The roof framing is usually timber, and the cladding may be a variety of materials including clay or concrete tiles, pressed sheet metal tiles, or corrugated iron. Gravity loads are carried by the walls in compression, and lateral earthquake forces are resisted by shear in the walls. This type of construction has not been permitted in New Zealand since about 1940.
Other countries#
Building typologies in the Pacific Islands can be quite variable, as are the different countries, communities, and ways of living. Nevertheless, as discussed in Vrolijks (1998), most of the houses constructed in this region are:
wood/timber frame houses;
traditional houses with round poles and thatched roofs and walls;
concrete block houses;
mixtures of traditional and ‘modern’ timber houses.
Roofs in traditional and wood constructions are generally light, and built with corrugated iron or thatched/leaf cladding.
Wood frame and traditional houses are the most common structures in these countries. Typically, these are well adapted to cope with earthquakes due to their ductility, except when they are built on top of short poles, common in places such as Fiji and Samoa. In some countries, notably in Vanuatu and some Micronesian countries, timber houses can also be constructed on concrete floor slabs.
The extent to which traditional construction is still applied varies widely in the region and within the country. In the Cook Islands, Tonga, and Marshall Islands, traditional housing is becoming scarce, while in PNG, Solomon Islands and Yap, traditional materials and construction types are still dominant. Within a country, these tend to be more common in rural areas, while structures built in more accessible regions are influenced by “modern” architecture, often using reinforced concrete or masonry confined with timber or concrete frames.
|
|---|
Traditional house in Vanuatu. Source: Ahmed and McDonnell (2020) |
|
|---|
Hybrid house in Vanuatu. Source: Ahmed and McDonnell (2020) |
|
|---|
“Modern” house in Vanuatu next to a traditional structure. Source: Ahmed and McDonnell (2020) |
|
|---|
Traditional house in Tonga. Source: Zamolyi (2015) |
|
|---|
Traditional house in Fiji. Source: Zamolyi (2015) |
|
|---|
Traditional house in Fiji before thatching. Source: Zamolyi (2015) |
|
|---|
Interior structure of a traditional house in Fiji. Source: Zamolyi (2015) |
