Colorbond Window Sills

The upper windows were taped up ready for rendering, the window header was patched up and ready to go when it became apparent how silly and difficult it would be to render the small patch of hemp between the window and the upturn of the roof flashing. In fact on all other windows the wall forming the sill slopes away from the window, but the wall forming the sill under the upper windows was made flat as it was too difficult to slope the sills when the walls were being made.

Upper windows ready for rendering

Tiny section of hemp between window and roof flashing

The solution was to get out the angle grinder and cut away the hemp wall so that it sloped down from the window to the top of the roof flashing. I then carefully measured the angle, which was slightly different for each window, and ordered some Colorbond angles from Kiteleys Roofing to be made up in the same colour as the roof to slot in under the bottom of the window then go over the roof flashing. The result was a very neat finish and it saved hours of fiddly rendering. I am also very confident that it will not leak.

Hemp wall cut off with an angle grinder

Installed flashing blends seamlessly with roof

Although the outside of the house had been left untended for about a year without any problems it seems that now some birds had decided to try and make a nest in the wall. Luckily they started on a weaker spot where a spacer hole had been filled and the spacer had been over one of the timber studs, which meant the birds were stopped by the stud and did not get all the way through the wall. It just showed us we needed to hurry up with the rendering.

Bird holes in hemp walls

Brett, our renderer was caught up with other jobs, but put in a weekend of work to try and get the walls finished. Significant progress was made with render going on around three of the five upper windows.

Front pavilion completely rendered

Render around upper windows on back pavilion done

 New techniques were also tried out. The hemp making up the window header above the long kitchen window was loose and crumbly, possibly because there was a very thick lintel behind the hemp, which was therefore separated into two parts rather than being able to key in each if the sides together. Screws with plastic washers had been used to try to help the wall stay together but thus did not assist with the crumbly window header. The solution was to mix up a slurry of sand and cement and flick it on the window header, using a special tool for the purpose. The cement helped hold the wall together enough to stop it crumbling, but only covered such a small area it would not affect the breathability of the walls. Once the cement slurry had set it was much easier to patch the gaps ready for rendering. The texture created will also help provide a key for the render to adhere to.

Cement slurry flicked on window header

Holes patched ready for render

The weekend of rendering meant that we only have three walls and the front door area left and the rendering of the whole house will be done. An exciting prospect.

East wall of back pavilion

House looks finished from the back

Render finished on the western side of the house

Help arrives at hemp building

On the last day of winter we began to share our hemp building skills. Tony, who we had met at Klara Marosszeky's Hemp Building Workshop in October 2011, joined us for the weekend. Braving an afternoon cold front that significantly dropped the temperature the three of us managed to do 18 mixes of hemp walling, working in some tricky areas under the noggins.

Saturday brought improved weather and further reinforcements, friends Martin and Nerida and Tony's son, Joel and Joel's partner, Alice. Our helpers picked up the mixing and tamping skills quickly and did a great job. As the walls got higher we used firstly milk crates and a plank as our scaffold and then a plank on a some steel stands. To fill and tamp the walls as they got higher we had to be able to both see down into the form work and be able to reach a hand or tamper down to even out and tamp the layers of hemp lime mix.

Hemping higher up the walls

Working in a section with several closely spaced studs

Once again we were working under window sills and noggins, but changes to the placement of form work made the work easier. The form work was at or just below the sill or noggin on the outside and about 12cm below the sill or noggin on the inside. This created enough room for an arm to reach under the noggin, but also allowed the hemp to be built up to and under the noggin on the outer side with the inside to be filled when the form work is moved up. Work was slow where there were lots of closely spaced studs, but difficult to get at sections were easier with one person spreading and tamping the hemp lime mix from the outside and another working from the inside.

Tamping under a window sill

Window sill - sloped down on the outside to shed water

There was great camaraderie and we set a new daily record of 26 mixes, bringing our overall total to date to 102 mixes. To achieve this we had five people working all day and extra two people for half a day, however when we had seven people two were moving form work up while the rest mixed and tamped the hemp. We have been using half a bale of hemp until it became light enough to lift on top of the other bales of hemp, this is so we could clear more floor space and gain access to more of the external walls so that we can form them up.

Layers of hemp - differing heights of layers due to location of noggins and windows

Layers of hemp finished over different weekends

Sunday was a glorious sunny spring day and this made the work of moving the form work up more pleasant, as did working with a tall helper. As the form work was moved higher up it became necessary to have two people to move it up. In one section the form work has been moved up to where it will join the eaves lining, we will probably have to do this section in small rises, with the form work lower on the inside.

Form work getting higher

Form work moved up, one section on outside to eves height

Hemp Walls Second Rise

Leaving behind a big storm in Sydney we spent the weekend in spring like weather at Culburra building more hemp walls. Friday we finished the first rise of the back bedroom and started the second rise up to under the noggins in the other bedroom. The form work was only moved up half a rise to just under the noggins so that we could tamp the hemp under the noggins. This was done by working in the usual method, including using a "L shaped tamper" to get under the noggins, up to about 5 to 10cm under the noggin when one side was built up and tamped before the other and we used our hands to push thee hemp  mix under the noggin . Once under the noggin was filled the other side could be filled and tamped in the usual way.

First rise finished

Hemping done up to noggins, outer form work moved up for next rise

We had no problems hemping around the water pipes and electricity wiring. The decision by Paul, the electrician, and I to mount the boxes for the electrical sockets so that they would be flush with the inside of the form work, meant that the only extra work was ensuring that the hemp was well tamped under the plastic boxes and around the conduit. Friday we set a new record, for two workers, getting 20 mixes done.

Saturday we only got 13 mixes done, deeper rises, window sills and more noggins were what slowed us up. We had moved the form work up to level with the window sill on the inside and just below the window sill on the outside, so that we could finish flush with the window sill on the inside and have a downward slope to shed rain on the outside. This made it very difficult to get the hemp in and even it out as the window sills were wider than the noggins. We learnt our lesson - in future we will raise the form work (or at least one side of it) up to about 12 - 15 mm below the sill or noggin, fill that section then raise the form work up and finish under the noggin where it is only about at hand's depth to make it easier to spread out the hemp mix.

Hemping under window sill

Hemping under noggin

The different levels of the sills and noggins has also meant that out rises can not always be even. Where we have had to finish at different levels we have done what we call a "ski slope" angling the hemp diagonally to avoid vertical lines. Where we did not do this at a joint the connection between the two sections of hemp looks weak and slightly less tamped - we will not do this again.

Good join - diagonal

Bad join - vertical

 Hemp building is more like cooking than I first thought. Our problem with the mix tending to stick and be pushed around the mixer was solved by putting the hemp in lightly - just like sifting flour. I originally thought that the sticking issue was due to mixes being too wet or dry, but when we measured out a few extra loads of hemp and stored them in some large buckets rather than the measuring buckets we had no problems with the mix. It appears that the pouring from one bucket to another and the slower pouring in from the larger buckets aerated the mix more, causing it to mix better and take up the water quicker so less leaked out the bottom of the mixer, needing to be re added. This resulted in well combined mixes with less effort.

Second rise done and form work ready for third

Warrain Beach and Lake Woolumboola from the lookout

Sunday morning we moved all the form work up ready for the third rise next weekend. Just to remind us why we are building near the beach we had lunch at the picnic table at Penguins Head Lookout and saw a seal floating around, flipper out of the water, near the rocks.

Seal swimming below Penguin Head