Violet Town Hemp House

Location:

Violet Town, Victoria

Type of Build:

Single story detached residence

Owner:

Neil and Sandy Garrett

Designer:

Neil Garrett

Builder:

Neil Garrett (Owner Builder)

Size:

24 squares (223m²)

Cost:

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

Climate:

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.     

Construction:

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.

Footings:

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.

Floor:

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.

Walls:

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

Windows:

Commercial double glazed aluminium windows and sliding doors.

Ceiling:

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

Roof:

Zincalume  with R1.5 foil backed blanket insulation/sarking over battens.

4.2Kwh  solar photovoltaic system on shed roof.

Heating:

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

Cooling:

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.

Formwork:

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

Advice/Recommendations:

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

Contact:

Phone 03 57981522

nesan@internode.on.net

Neil is Secretary of the Industrial Hemp Association of Victoria

He is happy to talk to and assist intending hemp builders

Nelligen Hemp Studio

Photo: Nicole Martin

Location:

Nelligen, NSW South Coast

Type of Build:

Two storey studio on rural block.

Owner:

Nicole Martin

Designer:

Nicole Martin

Builder:

Nicole Martin, Owner Builder

Size :

107m²  total; 63m² downstairs and 54m² upstairs loft.

Cost:

Est $200,000

Date of construction:

 April 2012 – est September 2015

Purpose of Build:

An artist’s studio. 

Choice of Material:

Nicole was interested in natural building materials for environmental and health reasons. She also wanted to build the studio herself and wanted the build to be low tech and manageable for an owner builder. Nicole looked into building with straw bales but was worried about vermin and that the width of the walls took up a lot of the floor space. She also looked into building with cob but decided that the material was too heavy to work with on the sloped location. Nicole found hemp through research on natural building techniques, hemp ticked all the boxes. It met the fire regulations, is resistant to termites, lightweight, environmentally responsible, able to be self built and provided a healthy breathable building. 

Nearing completion       Photo: Nicole Martin

Climate:

Zone 6 – Mild Temperate

Local Council:

Eurobodalla Council

Obtaining Approval:

No issue with Council as the build used a regular frame, met the fire code and BASIX, which were the issues that Council was concerned about. Nicole submitted the plans to Council with information about the hemp wall fire resistance and insulation value and no questions were asked about hemp.

Construction:

Nicole carried out the build as owner builder. She worked with a builder on site for 8 weeks to put up the frame, recycled posts and beams,  and the roof and rafters. A crane was brought in to put the large recycled wharf timbers in place. Nicole carried out the remainder of the build herself, except for the plumbing and electrical, with some help from friends and family.

Footings:

The concrete slab is half on ground and half suspended. The suspended slab is supported on a steel reinforced concrete filled concrete block wall on a concrete strip footing on concrete piers. 

Floor:

The ground floor is a concrete slab with ¼ strength black oxide.  The upper storey floor uses recycled  140mm Tasmanian Oak timber from a warehouse in Victoria.

Frame:

Partly large recycled Turpentine wharf timber posts and beams from the CSR factory in Sydney, and partly standard timber frame made off site at Lawmans Frame and Truss in Moruya. The upper floor joists are mixed hardwood from recycled telegraph poles.

Walls:

300mm hemp walls using AHMC (Australian Hemp Masonry Company) binder, with part of the east wall 500mm thick (due to a design change as this wall was originally going to be faced in stone). The walls are finished internally and externally with AHMC hemp lime render, applied in one coat about 10mm thick. No colour was added to the render and it has taken on the colour of the sand.

Under construction

Windows:

Locally made double glazed timber windows and glass doors. The windows have timber sills and storm mouldings ontop attached to the exposed timber lintels. The side window revels are rendered up to the window frame. Internal window reveals are rendered. Fibre cement permanent formwork was installed around the windows and doors.  

Ceiling:

Upstairs Gyprock; downstairs exposed bottom of upstairs recycled Turpentine floorboards.

Roof:

Corrugated Colorbond roofing in Windspray, over foil backed blanket sarking/insulation, with R3.5 sheep’s wool insulation between the rafters.   

Heating:

Nectre wood heater.   

Cooling:

The building uses only natural ventilation with the openable skylights drawing heat out of the house by convection.

Wall construction:

The walls construction was carried out by Nicole with help from friends and family, using a 120L electric pan mixer hired from a friend. Nicole gained experience helping a friend build their hemp walls.

Formwork:

Recycled OSB (oriented strand board). The frame was placed inside the hemp walls but was offset from the centre so that there would be deep window reveals on the inside. The inside walls were 150mm from the frame and the longest bugle batten screws were 150mm. To overcome this Nicole attached blocks of timber to the frame to attach the formwork to. With different sized gaps the use of spacers was awkward and Nicole abandoned them in favour of putting up the formwork using a level to space the formwork. The benefit of this was that there were no spacer holes to fill.

Section Diagram: 

Technical issues:

The offset frame and depth of the wall created issues that were resolved as above. The Gyprock ceiling was time consuming for a novice.The sheet bracing that was required because the building was located in a high wind area, was awkward to place hemp around and on the thin side caused the render to crack.

Advice/Recommendations:

Just do it.
Do not use sheet bracing, if need be find an engineer who can come up with a bracing solution that does not use sheet bracing.

Contact:

Nicole Martin

folkloreandco@outlook.com

Culburra Beach Hemp House

Photo: Nathan Devine

Location:

Culburra Beach, NSW South Coast

Type of Build:

Single storey detached residence.

Owner:

Kirstie  Wulf and Ben Schueler

Designer:

Kirstie Wulf, Shelter Building Design

Builder:

Owner builder

Size :

123m²  building, 55m² decks

Cost:

$210,000

Date of construction:

April 2012 - January 2015

Purpose of Build:

To provide a comfortable, natural, low energy holiday home with room for guests.

Choice of Material:

Kirstie was looking into natural building materials suitable for construction by an owner builder. She was investigating light earth (also known as light clay straw) when she found an article in Owner Builder magazine on hemp and liked the materials combination of insulation and thermal mass, the   

Climate:

Zone 6 – Mild Temperate

Local Council:

Shoalhaven Council

Obtaining Approval:

Although Shoalhaven Council had not come across hemp walls before the Council did not have an issue with them, but was quite picky about the wording of the Engineer’s report on the hemp walls and how it referred to the specific sections of the BCA. This held up Council approval by a few months. Council inspectors had no issue with the build during construction.

Construction:

The build was carried out by Kirstie and Ben as owner builders. The excavation, concrete slab, frame and frame erection, roof and plumbing and electrical were contracted out and Kirstie and Ben and generous friends constructed the walls and the internals and fit out. 

Footings:

Waffle Pod concrete slab on ground.  

Floor:

Polished concrete slab. The slab had 3% onyx oxide added making it a very dark grey. The top of the slab was lightly ground back to expose the mixed river stone in the slab in a “salt and pepper” look. Ceramic tiles were used in the bathrooms and laundry.

Frame:

Made off site by Truss-T –Frames at Bellambi, near Wollongong. The frame was erected by local builder, Rob Cheadle.

Walls:

200mm hemp masonry walls externally, constructed using AHMC binder, cast around a centrally placed 90mm structural pine frame. 10mm of AHMC hemp/lime render inside and out. Internal walls Magnesium oxide board finished with

Under construction

Windows:

Rylock thermally improved aluminium double glazed sliding doors and windows. Temporary formwork only used around windows and doors. External window reveals were rendered and sealed to the window with colour matched Sikaflex. Internally the Rylock windows came with an attached timber reveal. The revel was sized and the windows placed so that the render finished flush with the timber window reveal, avoiding the need for further trim and creating a minimalist look.

Ceiling:

Raked ceilings using hoop pine plywood, left unfinished with a 9mm black shadowline between sheets.  Higgins sheep’s wool insulation installed between rafters, R3.5 in kitchen/living/dining room and R3 in bedrooms and bathroom. Air cell R1.5 combined sarking, reflective foil and insulation installed on top of rafters under roof sheeting.

Main living / dining / kitchen area     Photo: Nathan Devine

Roof:

Colorbond custom orb (corrugated profile) in shale grey.

Heating:

 A gas bayonette has been installed but due to the house’s solar passive design and good insulation, to date the house has not required any heating in winter. 

Cooling:

Natural ventilation only. Doors and windows were placed to catch summer afternoon sea breezes and are left open on summer nights to cool down the thermal mass in the concrete slab.

Mosaic shower

Wall construction:

Kirstie attended a hemp building workshop with Klara Maroszekky from the AHMC and a workshop with Steve Allin (from Ireland) prior to commencing the build. The workshops both focussed on the mixing and placing of the hemp material, but lacked information on construction detailing to be used with hemp walls. 

Formwork:

OSB (oriented strand board) recycled from large packing crates, was used as formwork. The formwork was temporarily attached to the frame with coach bolts and spacers made from rigid conduit. The spacer holes were filled with hemp mix after the formwork was removed.

Section Diagram:

Technical issues:

Hemping up under the rafters was awkward but not impossible. Challenges were also faced with placing formwork and hemp in to small spaces, particularly in an area between two roofs. The frame had been constructed without any direction to the frame builders apart from the specification of 600mm centres for the studs. In a number of locations the presence of triple studs, particularly next to doors, meant that the hemp had nothing to key into and in some spots it pulled away from the frame as it dried. This was resolved by placing crews with large plastic washers through the wall into the frame pulling the hemp wall back to the frame. Dealing with long and thick lintels over large windows also posed some challenges, which with hindsight could have been avoided by using permanent formwork, but such a decision needed to have been made prior to the manufacture of the frame to allow for the extra thickness in the openings of the permanent formwork. Difficulties were also experienced with the application of the render, particularly on the MgO board. 

Advice/Recommendations:

In the design of the house the ease and ability to make the hemp walls needs to be taken into consideration. Similarly the house frame needs to be designed to work with the need for the hemp walls to key in around the frame. It is recommended to test several renders and colours before committing to a particular render.

Contact:

Kirstie Wulf

shelter@outlook.com.au

www.shelterbuildingdesign.com.au