Monday 18 May 2015

Hemp Building Costs



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.
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.

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

For more information and details on other hemp builds in Australia see www.hempbuilding.blogspot.com