THE GREAT WALL OF YOKINE

Anyone who has driven up Flinders St. in Yokine would hardly have missed the strawbale boundary wall on the corner property of Andrew and Gwen Carver. At five bales high and forty metres long, it has certainly been a show stopper. The number of bemused but enthusiastic reactions from passersby has been remarkable.

Even the buses were slowing down during construction so that passengers could have a look. People were at first stumped by the idea of strawbales as a building medium, but responded very positively when the process was explained. Many made the comment that it seemed the sort of thing that they would have done as a child, and that seemed to appeal to them. Mind you, if I hear another cow joke I'll scream!

The house that Andrew and Gwen live in is situated on a very busy road. The traffic noise is constant. Their daughter Sarah suggested a strawbale wall to give them some protection from all the sound, and as they had all done a strawbale course at one time or another, they decided to give it a go. Gary Dorn did the design work, and I was taken on to do the footings and supervise the wall raising and rendering. Peter Grant had done the survey work needed to locate the boundaries, so I and Dave Holley laid out where the footings were to go, then dug them and built the formwork that was required to raise the footing level 100mm above ground level. That took three days and eighty metres of salvaged 4"x2" Jarrah. On the fourth day we took delivery of 7.2m3 of concrete, poured that and inserted the metal locating pins and allthread. The strawbales had already been delivered by Stan Hughes, a farmer from Northam who takes his strawbaling quite seriously. He can even supply bales to various lengths such as half and three quarter. These had been stashed in the carport and the time had now come to get into the fun part.

A bunch of volunteers were assembled, the dampcourse goo painted on, and then the straw started to fly. By the end of the day the wall was up and pinned thoroughly with bamboo stakes. A great day was had by all, fuelled by a generous lunch that Andrew and Gwen put on. Sarah and her friend Gavin had come up from Denmark to be involved, and were able to display their bale shortening and stitching technique.

The next day we assembled the topplate, fitted it and tensioned it down. It consisted of the timber that had been used in formwork for the footing. Recycled recycled timber! Then in the afternoon the first batch of a lime putty and sand render was mixed and applied. A small amount of cement was added to quicken the drying time as it was being applied to the public side of the wall. By the end of the day about a quarter of the outside face of the wall and most of the workers were covered in render. The rendering continued over the weekend, and then another rendering session with volunteer labour took place the next weekend. Thanks to the efforts of Moss and Noni, my wife Lou, Helen Knewstubb and others, the outside of the wall, half the top, and some of the inside had received its first coat of render. Of course, over and above all of this, Andrew and Gwen had been rediscovering the joys of hard work, fresh air and that inner glow of achievement. Or something like that! What they have achieved, and the amount of hard work they have done is awesome, and something they should be proud of, I take my hat off to them.

The wall won't be finished for a while yet, and so the rendering process continues. The difference that the wall has made in blocking the traffic noise is remarkable. Dave and I nearly went nuts with all the racket whilst we were doing the footings. To sit in the garden now is to bearly know that there is even a road there at all. The organic nature of the wall and the soft limestone colour matches beautifully with the native garden, and creates a very pleasant atmosphere.

In a structural analysis four observations are to be made. The first is the amount of time that timberwork takes. The time required to build formwork and then the topplate can be easily underestimated. Next time I would allow a full day for the topplate assembly, fitting and tensioning. It takes the pressure off and any unexpected problems can dealt with without inconveniencing other workers.

  The second aspect is the tensioning system using the allthread and nut. I am not happy with this method as a serious amount of pressure cannot be gained without running the risk of stripping the nut or shearing the allthread somewhere along its length. Talking with John Glassford of Huff'n'Puff in N.S.W confirmed my suspicion that a tie-down system would work much more effectively, It turns out that the allthread system of tensioning went out the window over east some two or three years ago, and I can see why. Systems using gripple tensioners and other fencing-derived tools are now the norm. Fibrehouse, a Canadian company, has developed and patented a tensioning system using an inflatable sausage to compress the walls. John Glassford used this system when conducting his structural load bearing tests, and was very impressed. My only reservation about that system is that it runs the risk of removing the do-it-yourself aspect that I find very appealing about strawbale construction. Industrialization of a process can quickly become a disempowering experience for people if due care isn't taken. What I'd like to know though is why W.A. seems to be stuck in an information loop. There seems no advantage taken of new developments taking place over east or in other countries. Even the appropriate information doesn't seem to have hit the ground here. On top of that, there seems to be no questioning of methods used as experiences are gathered. My suspicion is that because people are taking the seemingly easy option of the infill method, then the tensioning system is not of great importance. This confirms the point that I made in in an article in the last edition. By not promoting loadbearing strawbale as the primary form of building, we are finding ourselves up an evolutionary cul-de-sac instead of being at the forefront of innovation. Whilst around the world people are developing vaulted loadbearing roofing systems, advanced tensioning devices and various methods and materials for rendering, we still seem to be fiddling around with bits of allthread. As a result of all of this I now have an appropriate tensioning system organized - not quite cutting edge technology, but at least up to date.

The third aspect are the footings. Freestanding walls don't need a huge footing so much as a keel as a yacht would have. Thus by using a "T" shaped footing, or a beam and pile arrangement, up to one third less concrete is needed along with a corresponding amount of digging. This can also apply to small structures. In larger structures a suitably engineered reinforced beam and pile footing would have real material and labour cost advantages over the traditional strip footing.

The fourth observation is probably the most important. Do not underestimate the amount of time spent rendering. Amongst all the claims made about the speed of raising a strawbale wall, this is the one factor that is either not recognised, or is glossed over. It seems to be a sin of ommission. Rendering is a labour intensive exercise that uses a lot of that valuable and expensive resource - time. Time is money, and to pay someone to apply two to three coats of render to maybe 200m2 of wall would be enough to blow a huge hole in any budget. The fact that rendering is easily within the realms of any person, including children, is both the saving grace and at the same time the achilles heel of strawbale construction. Don't be put off by this. The pastime of rendering is a contemplative and satisfiying way of passing time. The problem is that having seen 200 or more bales assembled into a wall in a day, the anticipation is that the rendering won't take much longer. Wrong. At a wild stab, I would suggest that for a day of wall raising, allow a week for rendering. Of course many hands will shorten that time, but always take Murphy into account when planning. This is when you really need all the volunteer help you can get. Bribery, pleading, threats of unspeakable acts, wheedling, taking of hostages - all's fair in love and rendering. It is vital that the first coat of render be applied as quickly as possible. The bales need protection from weather, vandals and fire. Once that scratch coat is on then you can relax. Because you need to allow about two weeks between coats you do get the breaks that you need, and so do friends and family. If you hold down a job I would seriously recommend taking leave to concentrate on this stage. Recognise also that many people may only have time on weekends to help.

Just to end on a technical note, we encountered a problem on the diagonal section of wall where it cut across the corner of the property. There was a fall of gradient of 300mm over eight metres. This meant that we had to step the footings so that we still had 300mm below ground but didn't increase the stem wall much more than the required 100mm above ground level. Of course this is easy with bricks as the step down is be done in increments of course height, in that case 85-90mm depending on mortar thickness. In the case of strawbales, course height is 360mm ! Over that eight metres we needed two 100mm steps. After much racking of brains and all sorts of improptu engineering solutions involving steel supports set in the footings, allthread set in the footings for attaching timber box section frames and so on, we decided to just step the footings the required 100mm and trust that a solution presented itself when we came to lay the bales. As a precaution we inserted allthread tie-down rods about eighteen inches either side of each step.

We laid the first course of bales and they neatly fitted the profile of the footings, with a 100mm height difference between the bales at the footing step-down points. What next ? Oh the joys of bales - a very flexible building material, quite literally. We placed the second course of bales, and where the bales straddled the step-down, they were bashed with a sledgehammer so that they duplicated the step in their middle. Because strawbales are made up of leaves or packets of straw, they will shear vertically. The strings still hold the bale together, but the bale itself can be stepped. The wall proceeded up in this fashion, appropriately pinned with bamboo stakes, and when we placed the final course, we fitted the top plate with an equivelant step. This was tensioned down on both sides of the step-down. This point of the wall proved just as strong as any other part of the wall.

So if for any reason you need to step a wall, but can't do it as a full course increment, don't panic. Just step down 100mm at a time and lay the bales as normal. If you have serious tensioning devices 12-18 inches either side of the step-down, you can maintain the same step-down in the top plate.

So all in all, a wonderful way of building. And do have a look at the wall sometime. You might even get to do some rendering!