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

Kyneton Hemp Bed and Breakfast

Rear view of studio

Location:

Kyneton, Victoria

Type of Build:

Two storey studio in heritage listed area, attached to rear of existing building.

Owner:

Joe and Deb D’Alo

Designer:

Ian Murray, Joe D’Alo and Deborah Varney

Builder:

Joe D’Alo

Size :

67.5m²  total; 40.5m² downstairs and 27m² upstairs.

Cost:

$165,000

Date of construction:

January 2012 to lock up stage in 4 months.  As a July 2014, still not finished, will need a further 2 months to complete

Purpose of Build:

To provide separate guest accommodation to be used as a Bed and Breakfast.  A unique experience for guests to stay in a hemp cottage.

Choice of Material:

Joe and Deb had been following the development of hemp construction for about 15 years. They have an interest in natural building and Joe had worked on both rammed earth and strawbale buildings. He saw the flaws with each of these construction types, such as the thickness of the walls for a strawbale building. Joe saw hemp construction as addressing some of the disadvantages of these other natural building methods, so with hemp also providing a combination of thermal mass and insulation, the choice of hemp for his own build was obvious. Hemp is an ideal building material for the climate in the region, as it has good thermal insulation whilst still providing some thermal mass for energy storage.

Timber rain screen finish

Climate:

Zone 7 – Cool Temperate

Local Council:

Macedon Ranges  Council

Obtaining Approval:

Council approval was granted for this build in a heritage area. A private certifier/building surveyor was used and there were no particular issues with the hemp construction.

Construction:

The whole build was carried out by Joe D’Alo who is a licensed builder. A carpenter with concrete formwork experience was employed. There was also a team for the hemp-lime mixing, filling the formwork and tamping.

Footings:

Concrete slab on ground. Concrete slab is a thickened edge raft slab with internal beams and expanded polystyrene edge insulation.

Floor:

The ground floor is tiles over concrete slab.  Upper storey – Alpaca carpet in bedroom and tiled bathroom. 

Frame:

Joe made the timber frame on site.

Walls:

Joe made the timber frame on site, using Australian Hemp Masonry Company (AHMC) binder, cast around 90mm structural pine frame. Internal walls were finished with a first coat of AHMC Binder and sand and a second coat of Plastalite lime/gypsum plaster. External walls were clad with Spruce Thermowood, which was left to naturally grey. For the external walls 25mm timber battens were fixed over the 10mm permanent magnesium oxide (MgO) boarding then clad with Spruce Thermowood weatherboards.  The 25mm gap between the MgO board and cladding creates an insulating layer.

Inside ground floor

Windows:

Double hung, double glazed timber windows. Permanent formwork was installed around the windows and doors.

Ceiling:

The exposed 20mm Supaboard Magnesium Oxide board floor of the upper storey acts as the ceiling to the ground floor.  Upper storey ceiling is 10mm Supaboard Magnesium Oxide board which was stopped and finished in a similar fashion as standard gyprock plaster then painted with a breathable paint. 250mm of “light hemp” (hemp wall material with less binder and no sand) was cast over the Magnesium oxide board as ceiling insulation.

Roof:

Corrugated galvanised metal sheet roofing is used.

Heating:

 A wood heater is planned to be used in an old fireplace, but Joe and Deb have found that the building stays warm in winter without heating.

Cooling:

The building uses only natural ventilation. Joe and Deb found that on a 40^o C day the downstairs of the studio stayed a much more comfortable 25 – 26^o C.

Upstairs under construction

Wall construction:

Joe is a licensed builder and carried out the wall construction himself, using a 360 litre diesel pan mixer hired from AHMC. Prior to construction Joe attended a Hempcrete workshop in Maleney, Queensland, but found the course lacked detail particularly when it came to how to specifically deal with window and door openings.

Formwork:

Magnesium oxide board was used as a permanent formwork on the external side of the wall. Formply was used for the internal formwork and rather than being attached to the frame it was braced against a timber stud on the floor so that there were no holes in the hemp wall. 

Section Diagram: 

Technical issues:

Hemping between the exposed upper floor joists was difficult. The 35^o ceiling was fine to work with but the 47^o ceiling was too steep and was awkward to build. Joe recommends that those interested in hemp building need to think about how to deal with window and door opening, in terms of lintels, flashing and how the render is to join the timber (window or door) frames.

Advice/Recommendations:

Joe found that using an external cladding and permanent formwork on one side of the hemp wall made the walls quick and easy to go up, because you only have to raise the formwork on one side, rather than both.  Although Formply was used as the formwork board, ply or OSB would have been quite suitable and cheaper. The external cladding was also advantageous from the point that the timber weatherboard cladding used maintained the look of the other outbuildings.  A rendered wall may have looked out of place.

Joe recommends runing electricals through conduit through the hemp walls. The mixing and tamping of the hemp-lime material is initially fun and therapeutic, however things can quickly change and the process can become a long and arduous task which will test people’s spirit.  A large, trained team might cost more in direct labour but the benefit will be in getting the hemp walls constructed quicker thus allowing them to dry (up to 6 weeks) before rendering.  The timing may be of particular importance if seasonal weather conditions are extreme.  Hemp lime building shouldn’t be undertaken when seasonal conditions are extreme, i.e., frost.

Contact:

Joe D’Alo

joe.dalo@bigpond.com