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