Saturday 11 May 2013

Nelligen Hemp Studio

The ANZAC day public holiday meant there was an extra day to build, so what else do you do when you are half way through building a house, we went and helped a friend build her studio. Nicole is building a hemp walled studio at Nelligen on the NSW South Coast. Approved by Council it is the first hemp build in the Eurobodalla Council area.

Nicole helped us out with building our hemp walls, so we wanted to repay the favour and I was keen to see how the studio was going. Her studio is being built in a beautiful location in a hill in Nelligen, with swamp and river views to the east and mountain views to the west.

View of the swamp
View out western window to the mountains
Nicole's build is different to ours in many ways and it shows that hemp walls can adapt to different styles. Nicole is building on a half suspended concrete slab, with a beautiful stone wall on the lower side. Her hemp walls are 300mm thick, to provide extra insulation in the cooler climate. To achieve deep window reveals on the inside she offset her frame toward the outside. The frame uses 90 x 35mm studs set at 450mm centres combined with large section recycled wharf timbers around the glass on the north side and as exposed beams supporting the first floor.

North and East side of the studio
Recycled wharf timbers
Nicole put up large sections of form work on the outside, avoiding the need to regularly move the form work up in the steeper sides of the studio. 600mm sections of form work were put up on the inside.

Form work on the steeper Western side
The use of 300mm thick walls was both easier and more difficult. It was definitely easier to place and tamp the hemp as there was no difficulty getting your arms and tampers around noggins and window sills. Nicole requested that her framing company put the noggins all in the same line, unlike my offset noggins. Noggins all in one row was definitely easier so that rises of hemp could be finished at the same point.

The smaller 45mm gap between the form work and studs was not a problem and plastic pipe spacers were cut to fit and she attached the form work with bugle-head batten screws. On the inside however, the larger gap between the studs and the form work meant that Nicole could not get bugle batten screws long enough to cover this distance and had to attach blocks of wood to her studs to be able to use the bugle batten screws to attach the form work. To complicate matters further the frame for her window openings were not the same distance from the form work as the frame and required different spacers.

Spacers with extra blocks of wood
Different sized spacers with window frame in background
Nicole used fibro as permanent shuttering around her window openings. If I build again I would do this, but would use something breathable like magnesium oxide board. I chose not to use this method, although it was recommended, as I wanted to curve the edge of my window openings. Nicole found a better way to do this by stopping the permanent shuttering a little bit short  of the edge, still allowing the edge of the window openings to be curved.

Permanent shuttering around window
Unfortunately Nicole has had to use sheet bracing, due to the high wind rating of the site and the second storey. Concerned about how the hemp will key into this she has attached some axe shaped blocks of wood to the sheets to give the hemp something to key into.

Sheet bracing
Nicole used Alcor as her damp proof course and I think this was a better choice than the embossed polyethylene I used. The Alcor keeps its shape when bent and was easier to turn down and hold in place.
Alcor flashing neatly turned down
Nicole is mostly using hemp that has come from the Ashford and and is a finer chop than the hemp sourced from Ecofibre in the Hunter Valley. The more finely chopped hemp seems to mix easier and tamp down more evenly. The pieces in the Ashford hemp were also more consistent in size. Given the choice I would use the more finely chopped Ashford hemp. Nicole also had her hemp in pre measured bags which made mixing much quicker. Nicole used the same Australian Hemp masonry Company binder we did. One bag of hemp was used with one bag of binder. This was a real advantage in her build since the thicker walls used up the hemp mix much quicker and the person mixing had a hard time keeping up with those filling and tamping. Nicole borrowed our pan mixer and this works well for a small crew of workers but with the thicker walls and easier placement of the hemp a large crew of workers would need a bigger mixer to work efficiently.

Finer chop of hemp
Hemp and binder mix
Pre measured bags of hemp
The sand Nicole used was a brownish yellow, rather than the grey Shoalhaven river sand we used. This meant that her walls were a warmer sandy colour when wet, but they look like they will still be a grayish white when dry, albeit with a brownish yellow tinge.

Hemp wall a few days old
Placing hemp walls
Nicole made a chook house with hemp over 12 months ago. It has been left unrendered since this time. The wall is only showing a very small amount of weathering on the bottom of the wall. This is very good as although the wall does not face the prevailing weather it only has small eaves.

Hemp walled chook house
Small amount of weathering on exposed hemp wall
I am looking forward to helping Nicole again and seeing how her studio progresses.

Western walls
Hemp walls in the afternoon sun

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