Hemping difficult locations

We had not hemped above some of the wider windows with large lintels as I was not sure how to provide extra support to the hemp above the windows as I was  not leaving a permanent form work. I eventually chose to use a wedge of wood sloping down toward the lintel to hold the hemp up and onto the wall where the lintel prevented the hemp keying in from one side of the frame to the other. This is an adaptation of the method used by Rodney Gregg on the Tasmanian hemp house, the walls he built were much thicker and so the timber pieces could be larger. Here I tried to get the timber as thin as possible using 35mm cut with a 45 degree angle and a small flat section at the bottom to attach it to the lintel. I found that the 45 degree angle made thee timber too tall and later used a 30 degree angle and found this just as effective. Extra care had to be taken to use a very thin tamper to put hemp in the 20mm gap between the timber and the form work, given that my walls are only spaced 55mm out from my frame on either side. So as not to cause a weak spot by this thin section of hemp I attached the timber pieces in several discontinuous sections above the window. 

First draft 45 degree timber section

Attached to the lintel on top of the temporary form work

We have been building the walls over weekend and so usually have a week or two gap between each time we see the walls however, over the Christmas/New Year break we spent 9 days building and got a chance to watch the walls dry out. For the first few days after the walls were cast they maintained the darker wet look, then quite suddenly took on a lighter dry look. For the pictured section of wall we also had to add in a hole in the wall for the wall mounted exhaust fan (the ceiling joists of this section were not deep enough for a ceiling mounted exhaust fan). The hole form work was made using some circles cut from OSB with ducting taped between and stuffed solid with scarp plastic packaging from the build. A little hole was cut in the ducting to take the electrical cabling for the exhaust fan. Hopefully we can leave the ducting in situ and use it for the fan.

Work done on 26 and 27 December

Dry by 3 January and hole for exhaust fan ducting

Not long before Christmas, Len, our plumber organised the Council inspection for the plumbing. The plumbing passed, no problems, but the council inspector picked up a problem with the frame. The ridge beam for the hallway was attached to just the studs and top of the door frame at either end. The inspector thought that over time the weight from the ridge beam may cause the top of the doors to sag. The answer was extra timber reinforcement. On each end of the hall I added what in effect became a timber lintel. I cut this into half the studs and made sure that it rested on a full length stud, which the door header did not. This was a difficult job in the standing frame, made more difficult on the second side I did by the need to avoid plumbing pipes and electrical cables. But my added lintels were securely held in to the board to which the ridge was attached and to the studs with, my favourite, batten screws.

Extra timber support added

As the walls have got higher we are having to lift the form work up higher, a job for which scaffolding has become a necessity.

Hemped above the kitchen window

Form work gets higher

When I drew the plans I always knew that the parapet wall above hall would be difficult to build and this proved correct. The location of the rafters meant that thee very top of the wall could only be done from the outside, which in this case was on top of the hall roof in a very small space.

Parapet wall form work in a small space

Form work right up to the rafters

Small risers were used to get closer and closer to the ceiling, then I had to work from the outside. I had to shimmy in under the the guttering and try to bend my arm at the right angle to shove and squash hemp into the last little bit of the wall.

Tight squeeze, bucket of hemp barely fitted

The most awkward possible position from which to build hemp walls

Despite the difficulty with the access for putting up the form work and the filling with hemp, the walls were well tamped and looked great. Just the spacer holes left to crawl back under to fill.

Hemped parapet wall

Inside the hallway

Other side of the photos above, showing no hint of the abutting wall

The protruding awning rafters  meant that form work had to be cut around each of rafters. This was done by measuring out the spacing and marking it on a lighter piece of timber, to avoid lifting up the heavier form work, cutting out the depth of the rafters and placing the form work up to the top of the rafters. Hemp was then placed in the form work and once the top of the rafters was reached an additional piece of form work ws added without removing the lower form work, this was so that no gap was left as the upper form work sat on top of the rafters.  

Form work cut around the awning rafters

The result on the inside was beautiful

With the skillion roofs we have lots of sloping walls to finish off to the roof line. As each rise reached the ceiling we have finished that section to the ceiling and continued along the rise. Like the other walls we have finished to the ceiling we mover the external form work up to the full height of the wall then finished the wall from the inside in two rises; the first with the internal form work up to just under the bottom of the top plate and hemp filled up and packed under the top plate and second with the form work up the the ceiling line allowing the hemp to be placed in beside and over the top of the top plate.

Formed up to the ceiling in the centre and just off the ceiling on the right

Wall fully formed up to the underside of the eaves on the outside

Parapet walls and tricky formwork

Last weekend we finished another wall up to ceiling height - the back wall of the main pavilion. This wall abuts the roof over the hallway and I knew it would be a difficult section. The over flashing for the hallway roof is already installed and finishes about 55mm- 60mm from the frame, the same distance that my form work needs to be from the frame. This meant that I had could not fit the form work sheet at the required 55 mm distance out from the frame. I trimmed one of the battens from the hall roof by awkwardly sawing upside down, then fitted the timber form work as close as possible and filled the gap with a bit of left over Jointex (stiff joint) from my concrete slab. The lightness of the hemp meant that the Jointex that was just wedged in place was not pushed out when the hemp was tamped.

Form work around parapet wall

Jointex filling the gap in the form work

Form work well fitted on top of over flashing

Some heavy rain and no downpipes meant that the rain and mud, under where the down pipe will be, splashed up on the hemp wall. The water did not soften or damage the hemp wall at all and it remained as hard and solid as the other walls.

Rain and mud splashed on the external wall

Completing the back wall meant working up to ceiling height. With our experience from the first wall we did this on, we did the last part of the wall in three stages. Firstly filling up to where our arms could just get into the form work, then raising the form work up to the full final height on the outside and just below the bottom of the top plat on the inside. We then filled under the top plate and up to the top of the top plate on the outside of the wall. Finally we moved the inside form work up to ceiling height and filled the remainder of the wall, going over the top of the top plate as the cut away in the eaves rafters has meant that the outside of the wall finishes above the top plate.

Filing under the top plate

As well as finishing the back wall of the main pavilion we did more work on the small sections at the front of the house and around the front door, which is yet to have the roof above it finished.

Completed back wall from the outside

Completed back wall from the inside

Front of the house taking shape

Front door

Final hemp walls started

Hemp walls now done on front of house

While the rest of the house was done up to door height, four small sections near the front door and large glass sliding doors had not even been started. Over the weekend we did two rises on each of these small sections, so now all the walls have been started. It was odd going back to the beginning and putting down the damp proof course and tamping into the set down in the concrete, but seemed much easier now then when we first started. The small sections were left to last as we tended to prioritise the long runs, but with lots of studs and noggins, and corners on three of the four sections, the sections may have been short but were very fiddly to tamp. Our friends, Ann and Will, helped the fiddly sections go up faster, while their children Daniel and Alexander kept our son well entertained.

The last sections to be started

 We also had to remove a section of concrete, now in the set down for the glass sliding doors, due to an error in the frame construction. It was nerve racking cutting into our beautiful concrete slab, trying not to damage our polished concrete floor, but with a new masonry cutting wheel on the angle grinder the cutting went smoothly. My fear of cutting into the steel reinforcing in the slab, came to be with a small section of steel being exposed. The circular wheel on the angle grinder could not cut a square corner so the last section was removed by hand with a hammer and chisel.

We had been concerned about the hemp sticking to the tall thin section between two glass sliding doors, as the section was just solid studs with no section where the hemp could meet up with that on the other side. We attached two of the bent up left over fascia brackets to each side of the column in the first rise and, on the side where there was no conduit, also in the second rise. Hopefully this will keep the hemp attached to the frame.

Tall thin section

Forming up began to get difficult as we reached the section where the wall with the hot water service intersects with the hallway roof. With some very tricky cutting we managed to put the form work up to half way through the roof intersection.

Back wall of the main pavilion

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