Finished hemp house |
I am often asked how the cost of building with hemp compares to other construction methods. Below I have provided a number of comparisons between the
cost of my hemp build and the cost of standard buildings. I can only provide information on the cost of my build rather than hemp building in general. My house was a custom design, an unusual shape and used many non standard materials, these things added to the cost, but we did much of the work ourselves bringing down the cost. My frame, hemp and
binder were purchased in 2012 and I am comparing it to the costs of building
provided in the Rawlinsons 2012 Building Costs Guide.
The timber frame I used was manufactured off site and
erected by a builder. The hemp was purchased in approx 100kg bulk bags from
Ecofibre. The bags were $80 (being $65 each plus $15 packing and handling) and freight from the Hunter Valley to the south cost was$1,800, which works out at $69 per bag. So the freight cost was almost half the cost of the hemp. My binder
was purchased from the Australian Hemp Masonry Company. It cost $15.10 per 9kg
bag including freight.
I purchased my own electric 120litre pan mixer from Aardwolf Australia at a cost of $1,685.20, and I have added this in when calculating the cost of the hemp walls. I was able to get my formwork very cheaply from e-bay, being a semi trailer load of packing crates with many sheets of OSB (oriented strand board) that I used for formwork. My cost for the formwork was $130 which is unrealistically low. I have also included the cost of all the screws, plastic washers, scales and other minor pieces of hardware to try to get a realistic cost of the walls, rather than just a cost of the major components.
I purchased my own electric 120litre pan mixer from Aardwolf Australia at a cost of $1,685.20, and I have added this in when calculating the cost of the hemp walls. I was able to get my formwork very cheaply from e-bay, being a semi trailer load of packing crates with many sheets of OSB (oriented strand board) that I used for formwork. My cost for the formwork was $130 which is unrealistically low. I have also included the cost of all the screws, plastic washers, scales and other minor pieces of hardware to try to get a realistic cost of the walls, rather than just a cost of the major components.
In relation to labour. I paid a builder to erect the frame.
All the hemp walls were made by myself, friends and family, hence there is no
labour component included in the cost of the walls. The house was rendered
internally and externally. I paid two different renderers to do the rendering. I
also had some internal walls non hemp that were rendered but when calculating the per square meter cost of the hemp walls I have only used the proportion applying to the hemp walls.
View down the North/East side of the house |
The total cost of my house including decks and landscaping was $239,000, but excluding decks and landscaping $228,000. The total cost includes the solar photovoltaics, water tank and all preliminary costs including my owner builder course and hemp workshops. The house is 123m2 so works out at $1,853 per m2. Some of the finishes on the my house would be considered medium and others high quality. I have also recalculated all the figures from the Rawlinson's Guide so that the figures below are all inclusive of GST. All costs are in Australian dollars and based on a build in Sydney.
Finish
|
Construction
|
Cost per m2
|
Medium standard finish
|
Framed
|
$1,573-$1,694
|
Medium standard finish
|
Brick Veneer
|
$1,699 - $1,831
|
Medium standard finish
|
Full Brick
|
$1,782 - $1,919
|
Medium/high standard finish – owner
built
|
Hemp
|
$1,830
|
High standard finish, no air
conditioning
|
Framed
|
$2,178 - $2,343
|
High standard finish, no air
conditioning
|
Brick Veneer
|
$2,376 - $2,563
|
High standard finish, no air
conditioning
|
Full Brick
|
$2,420 - $2,634
|
The following comparison is the overall cost of external walls and windows as Rawlinsons Guide does not separate the cost of external walls from the windows. My build had a lot of windows and they were all good quality double glazed units, therefore the cost of the windows was significantly higher than a standard build. Rawlinsons Guide estimates that the external walls and windows should be about 15% - 20% of the cost of the build, my external walls and windows were 25% of the cost of my build. My window order included eight sets of sliding doors, three triple pane and five double pane doors and 20 windows. This must be taken into account in looking at the figures below. The unusual design of my house meant that there was a lot of external wall for the floor area it enclosed, this would further skew the figures.
Finish
|
Construction
|
Cost of external walls and windows per m2 of floor plan
|
Percentage cost of build
|
Medium standard finish
|
Framed
|
$286.82
|
17.6%
|
Medium standard finish
|
Brick Veneer
|
$375.92
|
21.3%
|
Medium standard finish
|
Full Brick
|
$397.65
|
21.5%
|
High standard finish
|
Framed
|
$349.52
|
15.5%
|
Medium/high standard finish – many
double glazed windows and doors
|
Hemp
|
$469.91
|
25%
|
High standard finish
|
Brick Veneer
|
$494.17
|
20%
|
High standard finish
|
Full Brick
|
$509.02
|
20%
|
Prestige standard finish
|
Full brick
|
$554.95
|
17%
|
View of West side of the house |
To separate the cost of the hemp walling from other cost of the build the following is a comparison of my hemp walls 200mm thick with 10mm of render internally and externally, applied in one coat, with a 90mm timber frame @600 centres, with other standard walling systems. As we used our own labour to build the walls there is no labour component for the walls, however labour has been included for the rendering.
Given the unusual design of my house and the large amount of glazing looking at hemp walling per square meter of wall as compared to other construction systems I believe gives a better representation of the comparative cost of hemp walls.
For more information and details on other hemp builds in Australia see www.hempbuilding.blogspot.com
Given the unusual design of my house and the large amount of glazing looking at hemp walling per square meter of wall as compared to other construction systems I believe gives a better representation of the comparative cost of hemp walls.
External Wall Construction
|
Frame
|
Insulation
|
Internal lining
|
Cost of walls per m2 of wall
|
Corrugated steel
|
100mm timber @450 Centres
|
nil
|
painted plasterboard
|
$144.76
|
Corrugated steel
|
100mm timber @450 Centres
|
R2 glasswool
|
painted plasterboard
|
$161.20
|
Painted timber weatherboard
|
100mm timber @450 Centres
|
nil
|
painted plasterboard
|
$203.59
|
Painted timber weatherboard
|
100mm timber @450 Centres
|
R2 glasswool
|
painted plasterboard
|
$219.83
|
110mm brick veneer
|
100mm timber @450 Centres
|
nil
|
painted plasterboard
|
$208.67
|
110mm brick veneer cement rendered externally
|
100mm timber @450 Centres
|
nil
|
painted plasterboard
|
$247.06
|
110mm brick veneer
|
100mm timber @450 Centres
|
R2 glasswool
|
painted plasterboard
|
$225.11
|
Double brick (270mm cavity wall in
two 110mm skins)
|
nil
|
nil
|
plastered
|
$230.67
|
200mm Concrete block cement
rendered
|
nil
|
nil
|
plastered
|
$243.21
|
200mm hemp with 10mm hemp/lime render
|
90mm timber @600 Centres
|
nil extra but hemp inherently insulative
|
10mm hemp/lime render
|
$259.34
|
200mm hemp with 10mm hemp/lime render
|
100mm timber @450 Centres (cost
from Rawlinsons Costs Guide)
|
nil extra but hemp inherently insulative
|
10mm hemp/lime render
|
$227.00
|