First hemp wall

Finally I have started building my hemp masonry walls, but it almost did not happen. I had arranged for the ingredients for my hemp walls to all be delivered on Friday - Hemp, Binder and Sand (I already had the fourth ingredient, water, on site).

Shoalhaven river sand

About 7.30am Friday 5 tonnes of river sand arrived on a truck from Ison Home Hardware in South Nowra. The truck could only go on the driveway as the ground was very soft and wet from the rain, so it was left on a tarp and some builders plastic to one side of the driveway. River sand in the Shoalhaven area comes out of the Shoalhaven River and is unusually a dark grey colour. It was explained to me that this was from ash in the river from many bushfires.

Not sure when the other deliveries would arrive, I started working on the formwork. The area I chose to start on was a small section between a sliding door and a control joint. The control joint is required above where I have a control joint in the concrete slab. Control joints were put in the slab at two weak points to prevent cracking by allowing any movement to take place in the flexible joint filler. This then needs to be followed up vertically in the walls above the joint in the slab. Like the slab I will cast the walls in two sections, using the left over joint filler from the slab in between. This small section had lots of studs, a door jamb and a corner in it making the formwork quite fiddly. In the very tight section we used boards only 45cm high as it looked like it would be difficult to tamp if the formwork was any higher. I used 55mm spacers cut from old conduit with 100mm hex head coach screws. I drilled a hole in the board for the screw then used an impact driver to put the screw into the studs.

Corner formwork

 By lunchtime, no further deliveries had arrived and no phone calls either. Then I got the call from a Shoalhaven delivery company, that that had left four messages for me, but had been phoning me on the wrong number, so I obviously did not get these messages. They checked their invoice on which was my correct phone number. I was then told that the truck had gone out for the day, could they deliver on Monday. I explained that I would not be on site on Monday and I had arranged for helpers to be on site to help with the deliveries. They told me they would see what they could do.

In the meantime I phoned up to see where my hemp delivery was. I was assured that the delivery had been booked in, but at 2pm my hemp was still in the Hunter Valley. It appears that the transport company was having some difficulties. A few more phone calls throughout the afternoon and delivery was arranged for 7am Saturday. Sue from Ecofibre phoned me at 5.10pm to confirm that the transport company had picked up the hemp.

The afternoon was not wasted as I had also organised the Council inspection for the frame as I needed this done before I started covering it up with the hemp walling. The inspector arrived on time, looked at all the work, and the only changes I had to make were to add in two sections of diagonal metal strap bracing that had been specified by the engineer but not put on and to put a second nail in each piece of metal strap bracing where it crossed each stud. This was all dome and fixed before the binder arrived.

The truck carrying the binder worked past their usual 3pm knock off time to deliver my binder on Friday and it arrived at after 4pm. We had hoped that the truck could back up to the house and unload the pallets of binder onto the slab, unfortunately as the truck turned to reverse toward the house one of its front wheels came off the concrete driveway and almost got bogged in the soft ground beside the driveway. The truck only just managed to get out, leaving behind a trail of dirt and a big hole beside the driveway. The truck was not able to go off the concrete driveway, so the closest it could get was the end of the driveway. We had to move 5 tonnes of binder by hand.

Lucky escape for the truck

5 tonnes of binder waiting to be moved

The binder was in handy 9kg bags, making it easy to carry two at a time - a necessity when there were 520 bags to move! The midwinter light was fading as we moved the first pallet. A bright halogen builders light allowed us to work on in the dark. We finished moving all the binder into the house at 8.30pm just as a few spots of rain fell. Moving the binder only took 2 hours for two people, but work was interrupted by the need to bath and feed out three year old.  

I chose to use the Australian Hemp Masonry Company binder, as it comes premixed (easier when you are building a whole house), is made in Australia and has been well tested. We got the smaller 9kg bags of binder as we are using a 120 litre pan mixer, rather than a 300 litre mixer that can use 18kg bags. Klara from the Australian Hemp Masonry Company has also provided me with support getting Council approval and with building questions I have had.

`

Bag of binder

One pallet moved, four to go

The hemp from Ecofibre in the Hunter Valley arrived in a semi trailer at 7am on Saturday morning and it took up the whole floor of the semi with three more bulker bags stacked on top of each other. Matt the semi driver tried to back down the driveway, but the road was too narrow to turn in without damaging the lawn of the man across the road (who came out to make sure his lawn stayed in good condition) and some low electrical lines also made it tricky. So the bales needed to be unloaded from the roadside. We had originally thought we could roll the 110kg bags into the house, but after the first one was rolled off the truck we quickly discovered that this was not easy as the loosely packed bales did not roll well, flattening out on whichever side was on the ground. The bales were also too heavy and bulky for my partner and I to lift.

Matt the driver spotted a forklift working at the hardware store about 200m down the road, so I went down and asked if we could hire the forklift and driver for a short while. Unfortunately the forklift was not able to go off the premises, but JP at Culburra Beach Home Hardware did loan me his pallet jack, which turned out to be our saviour. Matt rolled each bale off the truck and it landed on one side on the pallet jack, we then took each bale up to the end of the concrete driveway. We could not leave the bales at the front of the driveway as we share it with the people who own the house in front of us. Once we go the the end of the driveway or where the bales had filled up to we just lowered the pallet jack and pulled the bales back upright and off the jack. The driveway was damp and very muddy from the truck that nearly got bogged the day before and the bales filled the whole of our section of the driveway.

The hemp truck unloads

Bale moving part one completed

While we were taking a short break after moving the bales onto the driveway, I received a call from Tony, a friend I had met doing the two hemp building workshops. He was stopping by to have a look at the house and was quickly roped into helping move the bale into the house. An extra person made it much easier to move the bales. As the ground between the driveway and the house was wet and muddy we made a temporary road out of OSB boards and a ramp up into the main pavilion of the house. The pallet jack could now be used as it needed a flat hard surface to work on. Each bale was tipped over onto its side onto the pallet jack, with two people pushing and one pulling the pallet jack we got up some speed, enough to make it up the ramp into the house without too much strain. With some careful stacking all 27 of the bales were brought into the house, in what became quite a smooth system of moving them. I am extraordinarily grateful to JP from Culburra Beach Home Hardware for the loan of the pallet jack and to Tony for helping move the bales and for having the great suggestion of leaving a small pathway between the bales at the end of the hall so we could at least walk through some of the house. The doorway from the main to the front pavilion is completely blocked with hemp bales.

Temporary road and ramp

Bales all safely moved into the house

By mid afternoon we had two sections of formwork up and made our first mix. For each 9kg bag of binder we had to weigh out 5.5kg of hemp. The hemp was incredibly light and we soon discovered that our scales, which only measured to the nearest 100g, were insufficiently accurate (hanging scales accurate to 10g have now been ordered through e-bay). The hemp has a pleasant barn-like agricultural smell to it and was easy to get from the bales into buckets.

The Aardwolf pan mixer was beautifully quiet when we tested it empty. The question was whether it would be as quiet with a full load - it was.  We added water, hemp, a bit more water, binder, then once it was well mixed, 8.5kg of sand. We added the water a bit at a time, until the mix looked and felt right, but will work of getting a more accurate water measure, bearing in mind that the amount of water will vary with the conditions. We wore gloves, dust masks and eye protection. With the binder in small bags it was easy to lift over the mixer and pour in slowly and this kept the dust down.

We got the mix out into flexible buckets, that could be shaped into a spout like shape to pour the hemp into the formwork, although in the narrower sections we put the hemp in by hand, which was quite inefficient. We will try and manufacture a scoop from a plastic milk container like they did at the Billen Cliffs house. The smaller tamper we had made worked well getting around the studs, even this was not small enough for some sections and we resorted to using using pieces of timber on end. Tamping down into the step down in the concrete and around the damp proof course was difficult and where a narrower tamper will be useful. The location of some of the spacers also made it difficult to tamp. The work was not heavy and we did two mixes making a wall about 45cm high.

The hemp looks like playground mulch

Test wall section

Mid Sunday morning we removed the formwork. From the top the wall looked very fibrous and like it might fall apart as soon as I took the formwork off, but when the formwork was removed, and it came off easily, the wall was surprisingly solid and straight. When the hemp is put in, in small layers of about 5cm deep and tamped evenly you can not see a line between one layer and the next. When we looked carefully at the wall there were a few spots where you could see a difference between each layer. The real problem was in the bottom corner where a spacer too close to the corner meant that the hemp was not tamped into the corner and just fell out. We will fix this when we fill in the holes left by the spacers.

Test hemp wall

Spacer too close to edge to tamp

A beautiful hemp wall

There is room for improvement, but the wall was not bad for a first go. We will do another test section before moving into full scale wall building. We are looking for volunteers to help build the hemp walls over August, September and October 2012, for more information e-mail culburrahemphouse@hotmail.com