Tuesday 15 January 2013

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

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