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1、This chapter gives an overview of the main materials, components and tools you will need to build with straw bales. Tie-down wire The strongly recommended practice is to tie down the walls to the foundations to make them stable and to minimise any tendency for them to settle over time. The best meth
2、od devised to date uses 2.5mm diameter (12.5 gauge) high tensile wire, which usually is available in 1500-metre rolls, more than enough for a typical domestic dwelling. Numerous alternatives for wall compression can be found in the literature, ranging from nothing (let the walls settle for weeks or
3、months before plasteringthe Nebraska style) to threaded rods inserted centrally for the full height of the wall. Tie-down with high tensile wire tends to be far superior to published alternatives. strawbale wall footing top plate wires anchored to footings various methods Fig. 4Wall tie-down geometr
4、y. Tie-down wires are anchored in the footings, pass over a top plate and are tensioned to increase the rigidity of the wall. 3 Materials, components and tools Top plates The compression wires are run over the top of the wall and down to the foundations. Since they are tightened to considerable tens
5、ion, something must be placed on top of the wall to prevent the wires cutting into the top bales. This top plate can take various forms. Most builders have used top plates in the form of heavy wooden ladders or wide planks of wood placed centrally on top of the wall. Even concrete beams have been ad
6、vocated. Such heavy-duty top plates are attractive for load-bearing walls, because they provide a rigid beam onto which the roof structure may be fixed. However, such facility is not required of the top plate in the case of in-fill walls. In fact, a much lighter, cheaper and more easily installed to
7、p plate can be used for both in-fill and load-bearing walls. This alternative is a steel ladder that can be made from 16mm to 25mm nominal bore (NB) steel pipe; 25mm NB pipe is the more appropriate size for load-bearing walls and will undergo less distortion for infill walls, which is particularly i
8、mportant when walls are tied down using the common fence strainer method, discussed later. The rungs of the ladder may be 12mm reinforcing bar or other relatively lightweight tube, pipe or rod; these rungs carry no significant load, since essentially they serve only to hold the pipes in position. Ho
9、wever, for load-bearing walls, steel plates (say 50mm 10mm section) may be welded between the pipes for attachment of the roof structure. Such steel top plates should be no wider than 300mm, and can be as narrow as 200mm. If the ladder is close to the 450mm width of the bales, it will be likely to s
10、lip over the edge of the wall in some places during the tensioning of the wires. As the wires are tensioned they will cut into edge of the top bales, but rather than being a disadvantage, this is desirable, because thereby the wire tension is applied more centrally to the wall, reducing the tendency
11、 for this force to cause the wall to tilt. These steel top plates can be fabricated very quickly on-site as needed using an electric welder and an angle grinder or hacksaw. (Be sure to keep the welding and angle grinders well away from any straw bales or loose straw, and have water or fire extinguis
12、hers handy in case of fire.) The materials are relatively cheap, especially if one uses downgraded pipe, which might have small defects that do not significantly affect its strength. Remember, this top plate will be completely buried in the final wall, so if it has surface rust or has some unattract
13、ive surface finish, that will be of no consequence. Another significant advantage of steel top plates is that they may be fabricated quite readily for curved walls (see Chapter 12 on creative shapes). Materials, components and tools11 Practical straw bale building12 Fig. 5Top plate alternatives. Top
14、 plates may be of wood or steel. A: Timber ladder top plate. B: Hardwood plank top plate. C: Steel pipe top plate. D: Modified steel pipe top plate for load bearing walls. A typically 90 ? 45 mm or 70 ? 45 mm timber ladder 450 mm 250 mm hardwood plank 25 mm C at least 16 mm NB better 25 mm NB e.g. 1
15、3 mm reinforcing bar welded to pipes 300 mm steel pipe A B C Intermediate structural units Structural units somewhat similar to top plates may be used at intermediate stages of wall construction, particularly as an aid in constructing high walls, and to provide anchorage for anything from shelving t
16、o artwork to drywall cladding. These units may be of simple, lightweight steel ladder structure, with the addition of strips of metal or wood at the wall surface (beneath the plaster) if they are to be used for anchorage. If they are only to assist in the construction of high walls, they can be a si
17、mple steel ladder structure, as described above. Intermediate structural units to be used for anchorage of drywall, shelving, etc. may be made from trench mesh that is the same width as the bales (usually 450mm) with lightweight steel angle (such as 51mm 30mm 3mm galvanised angle) tack-welded to the
18、 sides of the mesh. Since 450mm wide trench mesh generally is not available, if the full width is required (i.e. for anchorage on both wall faces) it has to be fabricated from reinforcing bar. However, if anchorage is required only on one face, then 300mm wide trench mesh may be used, with the steel
19、 angle fixed to only one edge. For the 300mm wide straw bales (to be introduced latersee page 64) these units can be made using standard 300mm wide trench mesh and the same lightweight steel angle, or 200mm trench mesh for single-side anchorage. Materials, components and tools13 D bolt roof structur
20、e to suitably-spaced plates modified steel pipe for load-bearing walls 10 ? 50 mm steel plate welded to pipes 300 mm at least 25 mm NB pipe D Wire locks Wire locks are devices that enable wires to be joined whilst allowing the wire to be re-tensioned. Available wire locks include the Wirelokmade by
21、Wirelok Ltd (NZ), and the Gripplemade by Gripple Ltd (UK). They have slightly different mechanisms but are similar in function. The wire locks have two holes that accept the wires but allow each wire to move only one way through the holes. Wire locks are used primarily for rural fencing as an altern
22、ative to using wire knots. It is not feasible to use knots for joining tie-down wires for straw bale walls, because every wire must by re- tensioned, usually a number of times. This is not possible with the wire knots. However, there might be occasions when two pieces of wire have to be joined in a
23、permanent, non-adjustable manner (e.g. a wire has been cut too short and it is not convenient to start over again). In such cases, an effective and very simple knot, which can be used with high tensile wire, is the figure-of- eight knot illustrated. Practical straw bale building14 steel angle e.g. 5
24、1 ? 30 ? 3 mm 12 mm reinforcing rod in form of trench mesh 200, 300 or 450 mm Fig. 6A design for intermediate structure units for anchorage of shelving, drywall cladding, etc. The steel angle may be welded to one or both edges, as required, but usually it would be on the inside edge only. Materials,
25、 components and tools15 Fig. 7Wire locks for joining 2.5 mm diameter high tensile wire. The Wirelok(top) is made by Wirelok Ltd (NZ) and the Gripple(bottom) is made by Gripple Ltd (UK). Fig. 8A figure-of-eight knot for joining high tensile wire. Make the knot as shown (top), then pull together (bott
26、om). Needles Special large needles are very useful when it comes to splitting straw bales, which is usually referred to loosely as cutting the bales, though the bales are not actually cut in most cases. The needle should be about 500mm long so it can be passed easily through the 350mm dimension, and
27、 also used through the 450mm dimension in case that becomes necessary. It should be made with two slots to carry twine through the bale by a pushfor one piece of twineand then a pull actionfor a second piece of twine. Holes may be used instead slots, but it is much quicker to drop the twine into a s
28、lot than to thread it through a hole. These needles can be made from 8mm diameter mild steel rod with a short piece of the same welded on one end to make a handle, or simply a bent end to form the handle. If the rod is smaller than 8mm diameter it can become too weak at the slots. The slots can be c
29、ut easily with a cutting disc on an angle grinder. Push-pull extractor The push-pull extractor can be useful if a deep hole is required in, or right through, an un-plastered wall, such as to install plumbing, though it is much better to install plumbing as the wall is being built. This tool is a som
30、ewhat fearsome device and requires some basic welding skills to make. An angle Practical straw bale building16 Fig. 9Needle used for threading twine through a bale when splitting bales. Twine may be inserted by both a push and pull action. grinder is also very useful. Near the end of an 8 or 10mm di
31、ameter mild steel rod, weld reverse-facing barbs made from heavy-duty nails, at least 3mm diameter, and sharpen the end of the rod to a point. Masonry nails are ideal as barbs, because they are hardened and therefore less likely to bend in use. This tool may be pushed into a bale quite readily, and
32、then, as the tool is withdrawn, the barbs drag out straw. A rapid push-pull action enables the removal of straw at a reasonable rate, though it still requires considerable effort to make a hole right through a wall. Wire tensioners A wire tensioner is necessary to tension wires for holding down and
33、compressing the walls. Traditional fence strainer Some practice is required to become a proficient user of the common type of fence strainer (also called a chain pull) used for rural fencing, but these tensioners are quite suitable, though not ideal, for tensioning wires on straw bale walls. The mai
34、n constraint is that the wire lock join should not be placed very close to the bottom or top of the wall, because for this type of wire strainer a substantial clear length of wire is required for easy operation of the strainer. Materials, components and tools17 Fig. 10A push-pull extractor tool, use
35、d for extracting straw from a wall to produce holes, such as for pipes. It may be made by welding masonry nails to a steel rod, with a suitable handle on the other end. This issue usually is of no concern for fencing, but it is significant in the more restricted space of straw bale building. The fai
36、rly cumbersome operation of these wire strainers, especially in confined spaces, makes somewhat inefficient the repeated attachment of the strainer during re-tensioning wires. Pop riveter as a strainer In the case of the Wirelok, wires may be tensioned using a pop-riveter gun, which is very convenie
37、nt in confined spaces. The pop-riveter gun enables only a small movement of wire for each operation of the gun, but the action can be repeated very quickly, so this is not a significant disadvantage. However, a pop- riveter gun cannot be used with Gripples, because the holes for the two wires are to
38、o close together, leaving insufficient room to attach the gun. Gripplestrainer There is a strainer specifically designed for use with Gripples. It overcomes the space problem and can be attached much more easily and quickly than the traditional fence strainer. In this case, and for the pop-riveter g
39、un, to enable re-tensioning of the wires, the waste wire must not be cut very close to the wire lock, because these strainers use this protruding piece of wire. Practical straw bale building18 Fig. 11Using a traditional fence strainer requires a bit of practice. New wrench strainer I have developed
40、a new strainer specifically for tensioning wires on straw bale walls. It overcomes the access problems, removes a problem due to friction between the wires and the top plate, enables very simple, accurate and quick re-tensioning of wires and requires only a standard wrench to operate. It forms part
41、of a new straw-bale-wall construction system (see Chapter 8). Wire spinner Since the high tensile wire usually is supplied in 1500 metre rolls and is very springy, when an attempt is made to unwind the wire it will tend to spring in every direction and a horrendous tangle is the likely consequence.
42、Therefore a wire spinner (available at rural suppliers) is essential for handling these rolls. Wire cutters Many ordinary pliers and wire cutters do not have long enough handles to provide the leverage necessary for easy cutting of high tensile wire. Mini bolt cutters with 300 mm-long handles and ha
43、rdened cutting edges will do the job more easily, and with greater safety for the tool and the operator. Materials, components and tools19 Fig. 12A wire spinner is essential for working with rolls of high tensile wire to prevent horrendous tangles. Staples There are many references in the literature
44、 to stitching wire mesh or metal lath to walls by threading twine or tie-wire through the wall so it may be used to pull wire mesh hard against the wall. There are also many references to stretching wire mesh across the face of the wall and fixing its edges, to timber for example, to enable the wire
45、 mesh to be held in tension. Quite apart from the fact that wire mesh or metal lath is not necessary in most situations, if it is used, generally it is not necessary to stretch it or hold it in tension, and the stitching procedure is very labour intensive compared with the use of staples. If the str
46、aw face is not a good cut face, stretching wire mesh across the face can make plastering easier, but if the straw has a good cut face, stapling the wire mesh to the wall face is entirely adequate. Staples can be made from the same high tensile wire as is used for compressing the walls by cutting 500
47、mm lengths of the wire and bending them into a U shape. These can be used to hold wire mesh in place simply by pushing the staples through the mesh into the wall. They can also be used for such purposes as holding electrical plaster plates in place (see page 83), and to secure temporarily the edges
48、of plastic sheet, as on the top of garden walls (see page 88). Mallet A large wooden mallet is almost essential for straightening straw bale walls that are built by the usual current methods, but a new method (see Chapter 8) eliminates the need for such mallets. Brush cutter/cord or string trimmer S
49、traw bales do not lend themselves to trimming and shaping by the usual carpentry and building tools. There are a number of tools that can be used for this purpose, including: hedge cutters, cord trimmers, chain saws and brush cutters. Chain saws are not very suitable. Apart from their being particularly dangerous in inexperienced hands, the cut straw can easily enter the drive Practical straw bale building20 Safety warning The high tensile wire is very springy and therefore can easily flick into the users eyes and cause serious damage. Take great c