Wednesday 12 June 2013

Hemp Lime Rendering Commenced and Nelligen Studio Revisited

A busy long weekend was spent,  finishing the wardrobe in the front room and putting on the door jamb and inbuilt pelmet for the curtain that will be the wardrobe door. I used Tasmanian Oak timber, as I had for the other door jambs on the house, cut to size to provide a render stop for the 10mm of render on each side of the wall. The ceiling and door jamb was then covered in plastic, reusing the plastic bags the insulation came in, to protect them from the render.

Our friends Martin and Nerida stopped in on an unwintery warm sunny Saturday with their chainsaw  and we cut up some very sizable tree branches that had fallen onto the block over the previous 12 months, most significantly the branch that dented the fence and the other that cut a hole in the back gate. They left with a trailer load of firewood , but not before I had roped Martin in to help me with the battens and valley boards for the awning over the front door. The tricky part with this was that the section of the awning over the front door only has two rafters, one of which is the valley rafter. Because we needed to put the valley boards in next to this rafter we could not attach the battens to it. Instead, we used left over material from the awning rafters to create perpendicular rafters that ran between the two rafters and on top of which we attached the battens. Over the rest of the weekend we finished the battens, valley boards and hip battens for the whole front section of the house. 

Valley boards and battens with extra support installed
Battens and hip batten installed
Being a long weekend we took a trip down to Nelligen to help our friend Nicole with her hemp walled studio. She had made good progress since we had last been on site. We spent the day helping her build the hemp walls along he south wall and above the stone foundation wall. The east wall above the stone foundation was originally to be made of stone but a change of plans after the frame was made meant that adaptations had to be made to change the originally 500mm walls to be partly 300mm and 500mm. The thicker walls used up the hemp very quickly.

Stone foundation wall and formwork for hemping

The west and part of the south wall are completed up to door height.

West wall
West and south walls
With all the different spacer sizes she was using, Nicole abandoned the use of spacers and instead used a level to ensure the formwork went up vertical from the lower measured section of the wall.

Formwork being filled with hemp
Sheet bracing filled on both sides
Permanent formwork around windows
Nicole's hemp came from two different sources. The first sections of wall used hemp from Ashford and the current sections she is making use hemp from the Hunter Valley. Although I also sourced my hemp from Ecofibre in the Hunter Valley it was very different from the hemp Nicole was now using. Her hemp came in compressed bales and was much finer than the hemp I got from the Hunter Valley and was even finer that the hemp from Ashford. Having worked with all three different chops of hemp, my current preference is for the chop from Ashford. The larger pieces of hemp from the Hunter Valley did not interlock as well as the finer chop, but the very fine chop from the Hunter Valley appeared to compress so much together that the walls seemed quite dense. The Ashford hemp seemed to be a balance between the two. However, I will reserve my final judgement until Nicole's walls are thoroughly dry and the properties of the walls using the different hemp can be better observed.
Compressed bale of Hunter Valley hemp
Wall using Ashford hemp
Wall using Hunter Valley hemp
Hunter Valley finer chop of hemp
Nicole loaned us he old cement mixer for our rendering and John the renderer came around to try out the hemp lime mix. John made up the mix a bit runnier that I had done the test samples, but that may explain why I had some difficulty applying the render on my test samples.

Hemp lime render being mixed
Render ready to go on the wall
Self adhesive fibreglass mesh was applied to the joints between the hemp and MgO boards.
 John first tried out the render on the inside of one of the wardrobes, the top section of which was a very awkward area to access. Perhaps this was not the best place to start, but it was an easy place to hide any mistakes that were made. John found the hemp lime render different to any other product he had used. He found that it was best to put the render on at as closest to the final thickness as possible, float it and them leave it. Floating the render again later, as is done with cement render just brought up the grains of sand and made the finish less smooth. Unexpectedly the render did not cover anywhere near the 5sqm advised by the manufacturer. When we next do a larger section of wall we will more accurately measure the square meterage covered by each bag of render. John was able to get the finish we wanted to achieve, a consistent but not completely flat finish, just like a traditional lime rendered building.

Render mesh applied to joints
Rendering the inside of the wardrobe
Awkward top section of the wardrobe
We need to get the inverter for our solar panels installed by 30 June, to take advantage of the government rebates that were in palace when the panels were first installed. So, John did a patch of render where the inverter will be placed. John was unsure of the best way to render the MgO boards and whether the render worked better with or without render mesh so he did some tests, doing a 10mm coat of render mesh, a skim coat on render mesh and the same again 10mm coat and skim coat without render mesh. The skim coat is a thin coat that is later covered with the finish coat of render. When dry we will be able to see which method provides the best adhesion.

Render patch for solar inverter
Skim coat and 10mm coat on render mesh
Top to bottom; skim coat no mesh, 10mm coat, skim coat with mesh, 10mm coat with mesh all on MgO board

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