Tuesday, 4 August 2015

Violet Town Hemp House

Violet Town, Victoria

Type of Build:
Single story detached residence

Neil and Sandy Garrett

Neil Garrett

Neil Garrett (Owner Builder)

24 squares (223m2)

Est $200,000

Date of construction:
Commenced  2013 est. completion 2015

Purpose of Build:
2/3 bedroom residential home

Choice of Material:
Neil and Sandy had read about hemp building and first saw a sample at the Hemp Embassy in Nimbin. They had stayed at “Bramare” a rammed earth house in Bendigo run by the Otis Foundation for people recovering from breast cancer. They loved the feel of the house and the colour. They investigated rammed earth, but it looked like a lot of work for owner builders. Hemp used a similar technique of creating a monolithic wall using a system of shuttering and had the added benefit of being insulative. Neil and Sandy have used natural materials throughout the build, choosing to build with plantation timber, avoiding rainforest timber or hardwood. They have also reused materials and used pre owned or reject materials, giving them a new life.
Oxides used to colour different mixes
Zone 7 - Cool Temperate

Local Council:
Strathbogie Council but did not use

Obtaining Approval:
The building permit was obtained on the basis that the Hempcrete product was certified to conform with the requirements of the BCA. The private building surveyor assessed the structural plans as suitable, then the hemp was passed as it was just infill. The house needed to meet 6 energy stars and did so with 250mm hemp walls, giving a R rating of 3.5 to 4.     

All work carried out by Neil and Sandy Garrett, except for plumbing and electrical. To build Neil used St Astier (French) binder supplied by Hempcrete Australia. He has been experimenting in recent constructions with binder recipes making it from local materials with good results.

Concrete slab on ground, to the north.  Slab is 100mm thick with edge beam and has 50mm expanded polystyrene slab edge insulation. To the south timber bearers and joists, with silver streak insulation under joists, brick perimeter wall on concrete strip footing. No termite barrier as T2 termite treated timber used for frame, subfloor and roof.

It was intended to polish the concrete slab to the north but have decided on a floating bamboo floor for comfort levels. Timber floor with silver streak insulation under joists to the south.

250mm hemp walls, using St Astier (French) binder supplied by Hempcrete Australia, cast around 90mm by 45mm F5 T2 pine frame at 600 centres. Render; sand, lime and blast furnace slag.
Beautiful curved corners
Commercial double glazed aluminium windows and sliding doors.

Painted 3mm Magnesium Oxide board, with R 3.5 fibreglass insulation between rafters, with 50mm air gap to the 50mm blanket above.

Zincalume  with R1.5 foil backed blanket insulation/sarking over battens.
4.2Kwh  solar photovoltaic system on shed roof.

Freestanding European high efficiency slow combustion stove wood heater, with soapstone surround as heat bank.

Fans, natural ventilation and a reverse cycle air conditioning to be installed if required.

Wall construction:
Neil and Sandy made the walls themselves, using their own 120L mortar mixer. Neil attended a workshop with Hempcrete Australia and became a licensed installer. Neil periodically holds hemp building workshops.

18mm form ply, strengthened with 35 x 75mm pine battens. Formwork attached to frame with bugle batten screws. 

Section Diagram:
Technical issues:
Do not render too soon! Allow the walls to fully dry out before rendering, to avoid cracks in the render. If building again Neil would not use as much Magnesium Oxide board, he would only use it in the wet areas but not other walls

Talk to other hemp builders. You can do the work yourself; building with hemp is very satisfying, low skill and forgiving.

Phone 03 57981522
Neil is Secretary of the Industrial Hemp Association of Victoria
He is happy to talk to and assist intending hemp builders