Latest data from a long-running FWPA project demonstrates the average one and two storey detached house in Australia used 14.58 m3 of wood in 2017-18.
Numbers are all equal, but some matter a whole lot more than others. Douglas Adams famously reported that the answer to life, the universe and everything was 42, a number he made up because the question was utterly futile.
Far more tractable, but long elusive, the answer to how much wood is used in the average house has finally been answered. The long-running FWPA ‘Timber Usage in Residential Construction’ project has analysed around 4,500 building plans for 2017-18 and yielded the 14.58 m3 result.
Here is an edited extract of an update summary for the still-continuing project.
FWPA data aggregation program has robust monthly information of the type of softwood products sold each month. Understanding the end use markets including application in new house construction has been limited.
Research projects have been undertaken in the past to assess the timber usage based on an assessment of the bill of materials (BoM) of model homes built by project home builders. (Refer: Dynamics of Carbon Stocks in Timber in Australian Residential Housing, M. Kapambwe, F. Ximenes, P. Vinden, R. Keenan, FWPA May 2009)
Other research which informs timber usage has been projects relating to the lifecycle assessment of alternative building materials. (Refer: A Comparative Life Cycle Assessment of Alternative Constructions of a Typical Australian House Design, Andrew Carre, FWPA March 2011)
In the US market, the National Association of Home Builders undertakes an annual review using a combination of materials take off data generated from standard homes reviewed by quantity surveyors. This data is completed by surveys of some 50,000 builders across all states. From this research effort complete information is available on the quantity of materials used by application, material type and end section.
To build on the earlier work FWPA has undertaken a project to gather from residential building plans detailed information on:
- Dimensions – Lineal Metres and Square Metres
- Materials – by type and grade and end section
This information has been used to calculate volumes of materials used.
Data was extracted from building plans provided from two sources and protocols were in place to protect the intellectual property of the building design. However, as those sources did not cover the entire population of building approval projects, a number of statistical techniques were used to create a meaningful sample.
The sample was drawn from a pool of nearly 20,000 building plans for the 2017-18 period for NSW, Queensland and Victoria. Plans were selected at random from a stratified sample designed to reflect ABS monthly housing approvals by LGA (Metro and Regional) and building type (detached house, Town House, Multi-Res). The final sample reconciled to the ABS approvals data as follows:
1) The actual sample proportion of Metro and Regional LGA in the ABS approvals
*Only includes LGAs for Brisbane
2) Comparison actual sample proportion of building types with the ABS approvals
Other quality control checks were undertaken to reconcile the results with the ABS annual survey of Characteristics of new residential dwellings. The ABS does not differentiate between 1 and 2 storey dwellings, so a weighting was applied to the FWPA average for m2 for 1 storey and 2 storey homes.
This was used to compare the FWPA and the ABS results for 2017-18 period. These results are reasonably close and provide confidence that the FWPA sample of building plans is statistically robust.
|
Houses 1&2 Storey |
FWPA |
ABS |
|
NSW |
231.5 |
220.3 |
|
QLD |
218.4 |
230.8 |
|
VIC |
232.8 |
244.8 |
Source: ABS Report Characteristics of new residential construction
So, against that background what were the results?
The data collection process covered most aspects of residential building construction which is summarised as follows for the average of all detached housing projects (1 and 2 storey) for Australia:
All Products
|
Australia |
Projects |
1 storey detached |
Volume |
|
Projects |
2 storey detached |
Volume |
|
|
|
LM/m2 |
m3 |
|
|
LM/m2 |
m3 |
|
Floor Structure |
28 |
|
4.25 |
Floor Structure |
59 |
|
5.28 |
|
Wall Framing |
1,117 |
140.7 |
5.98 |
Wall Framing |
2,375 |
205.0 |
8.75 |
|
Lintels |
1,177 |
22.3 |
0.20 |
Lintels |
2,375 |
34.99 |
0.26 |
|
Roof Trusses |
3,553 |
238.1 |
5.43 |
Roof Trusses |
3,553 |
238.1 |
5.43 |
|
Door Jambs |
1,177 |
107.1 |
0.14 |
Door Jambs |
2,376 |
149.1 |
0.20 |
|
Architraves |
1,177 |
126.7 |
0.10 |
Architraves |
2,376 |
193.6 |
0.15 |
|
Skirts |
1,177 |
192 |
0.23 |
Skirts |
2,376 |
276.5 |
0.33 |
|
1 Storey |
2 Storey |
||||||
|
Total m3 (less flooring structure) |
12.09 |
Total m3 |
|
|
20.40 |
||
Weighted Average m3 per house
Using the following data a weighted average for houses in the FWPA data set can be calculated as follows:
All Products
|
Weighted Av Australia |
m3 |
m2 |
Ratio |
Weighted m2 1:2 storey |
m3 per m2 |
Weighted Av ratio: 1:2 storey |
|
1 storey |
12.09 |
189 |
70% |
132.3 |
0.06394 |
8.46 m3 |
|
2 storey |
20.40 |
289 |
30% |
86.7 |
0.07058 |
6.12 m3 |
|
219 m2 |
14.58 m3 |
The Weighted Average of 1 and 2 storey detached homes is therefore 14.58 m3.
As outlined above, this is a continuing project of the FWPA, one that will deliver results for subsequent years, to be compared with the 2017-18 data. For a full copy of the report please contact Kevin Peachey, Statistics and Economics Manager, kevin.peachey@fwpa.com.au
