Abstract:
Systems and methods of internally bracing straw bales during construction of a straw bale wall using ladder structures that eliminate the need for external bracing and form a permanent part of the wall&#39;s internal structure.

Description:
This application claims the benefit of U.S. Provisional Application No.: 60/446,731 filing date Feb. 10, 2003. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates systems and methods for constructing straw bale core building walls and, more particularly, to such walls with internal structural components that can brace the wall during construction. 
     The use of straw bales as a core material for building walls is well known in the art, as are the advantages of such walls. One of the difficulties of constructing such walls is keeping them in place and plumb while they are being erected and before an outer membrane is applied. 
     The prior art practice for keeping straw bale walls in place during construction is to use external bracing, primarily using wood or pipe members. The disadvantages of external bracing (regardless of the materials used) is that the bracing makes the application of the outer membrane difficult, requiring substantial effort and time, which translates directly into added expense. External bracing also consumes materials that are typically discarded. Even if some of the bracing materials are reused or recycled, they add nothing to the structural integrity of the wall after it is fully constructed. 
     The present invention teaches a system and method for the construction of a straw bale core wall that provides internal bracing during construction that permits walls as high as 24 feet to be constructed with little or no external bracing, and the members and parts that provide the construction phase bracing also become permanent parts of the wall&#39;s internal structure. The present invention thus eliminates the difficulties of applying the outer wall membrane when external bracing is in place and uses the same members that provide construction phase bracing as internal structural elements for the finished wall. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In the present invention, a wall is constructed using straw bales as a core material. Generally, straw bales are stacked in courses (levels or tiers) in a running bond (a pattern in which the bales of one course are offset one-half bale relative to the bales in the adjacent courses) to the desired height of the building wall and then a membrane is formed to encapsulate the bales. Typically, the membrane is concrete that is pneumatically placed (e.g., shotcrete or gunnite) onto the bales, covering them on both sides to a thickness of 3 inches (for example), creating an exterior membrane and exterior wall surface and an interior membrane and interior wall surface. Metal members that perform a dual function hold the bales in place while they are being stacked and before the membrane is applied. These members keep the stacked bales aligned and upright to a height of up to 24 feet without external bracing and provide the wall with an internal structure that ties the exterior membrane and the interior membrane together to form an extremely strong and durable wall structure independent of the straw bales which function primarily to provide formwork and insulation. 
     The invention achieves its outstanding results by the strategic placement (both vertically and horizontally) and interconnection of a plurality of ladder structures (trusses) and various tying members. These ladder structures are placed within and immediately adjacent the stacked bales to give the bale walls sufficient out-of-plane strength to remain erect and plumb during construction before the outer membrane is applied and while the outer membrane is applied. When the concrete membrane is applied forming the interior and exterior concrete membranes and wall surfaces, the ladder structures remain in place as part of the inner wall, performing vital structural functions. 
     The present invention permits the membranes to be applied without the need to work around external bracing, greatly simplifying that process. It follows, of course, that erecting and dismantling external bracing is eliminated, as are the substantial costs and waste associated therewith. 
     One of the outstanding features of the present invention is that a wall of any height (from 8 feet to 35 feet) can be assembled from small parts which are easily transported to the site and which can be easily stiffened and braced without the need to break the bale bond or change the details. Spars and vertical rebar members are tied or tack welded to form a stiff truss system that stabilizes the wall during construction. For additional stiffness and to help keep the wall true over a length, the same system is used horizontally at any horizontal joint (between a course of bales). Special ladders with narrower dimensions are fabricated for this purpose so that they fit within the vertical system. The vertical spar/truss system of the invention, coupled with a horizontal stiffener at the top course, suffices for walls up to 12 feet in height. For taller walls, a horizontal stiffener is placed either at 12 foot intervals or at a height equal to half the wall height, whichever is less. 
     Accordingly, it is an object of the present invention to provide internal bracing systems and methods for constructing a straw bale wall. 
     It is another object of the present invention to provide internal bracing and methods for constructing a straw bale wall to a height of 24 feet without the need for external bracing. 
     Yet another object of the present invention is to provide systems and methods for constructing a straw bale wall in which permanent internal structural elements act as bracing during construction. 
     The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a partial straw bale core wall with portions broken away to expose certain parts of the external structure of the wall and foundation; 
         FIG. 2  is a perspective view of a typical bale and connecting spar used in connection with the invention; 
         FIG. 3  is an end section view of the foundation wall for the wall of the invention; 
         FIG. 4  is a side view of a portion of a wall on which bracing ladders have been erected; 
         FIG. 5  is a plan view of  FIG. 4 ; 
         FIG. 6  is a front view of a bracing ladder of the present invention; 
         FIG. 7  is a side view of  FIG. 6 ; 
         FIG. 8  is a front view of a portion of an alternative embodiment of a bracing ladder of the present invention; 
         FIG. 9  is a perspective view illustrating four bales in a running bond configuration with stabilizing spars; 
         FIG. 10  is a semi-schematic side view of a portion of a wall onto which five courses of bales have been stacked; 
         FIG. 11  is the same as  FIG. 10 , with the addition of a horizontal stiffening ladder; 
         FIG. 12  is a plan view of a stiffening ladder; 
         FIG. 13  is the same as  FIG. 12 , with additional bales shown stacked on top of the stiffening ladder; 
         FIG. 14  is the same as  FIG. 13 , with connecting rods added; 
         FIG. 15  is a plan view illustrating a clamp connecting two rebar parts together; 
         FIG. 16  is a plan view showing two rebar pieces secured together by a wire twist tie; 
         FIG. 17  is the same as  FIG. 4 , but including a corner of the foundation wall and a corner bracing ladder; 
         FIG. 18  is a plan view of  FIG. 17 ; 
         FIG. 19  is an end view of the foundation wall onto which a single course of straw bales has been stacked, together with a bracing spar and connecting rods; 
         FIG. 20  is an end view of the wall of the present invention showing the foundation and the bond beam; and 
         FIG. 21  is the same as  FIG. 14 , with the addition of welded wire fabric covering the interior structure of the wall. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description includes specific measurements for purposes of illustration only and, except where otherwise indicated, such specific measurements are not to be taken as a limitation of the invention. For example, the description of the invention is with regard to the use of standard California rice straw bales 16 inches wide by 24 inches high by 48 inches long. These dimensions will dictate certain dimensions for the various metal members of the invention, as well as their spacing. It will be clear to those skilled in the art that should a straw bale of different dimensions be used, the dimensions of the various metal members and their spacing could, and likely would, change accordingly. What does not change is the functional relationship of the various members to one another. 
     Referring to  FIGS. 1 and 2 , a straw bale wall  11 , according to the present invention, is constructed on a foundation wall  12  by stacking straw bales  13  in a running bond within a bracing system  14  of various metal components described in detail below. The bond of bales and bracing system are enclosed by a membrane  16  creating an inner wall surface  16   a  and an outer wall surface  16   b  which are joined at the top of the wall by a bond beam  15 . 
     The metal bracing components  14 , which are described in greater detail below, provide all of the bracing necessary during construction so that the application of the membrane  16  (e.g., shotcrete, gunnite or the like) is unencumbered by external bracing members. B 1   
     Each of the straw bales  13  which form the core of the wall  11  are parallelepipeds having a height  13 H, a length  13 L terminating in opposing ends  13 E, and a width or thickness  13 W. The invention will be described with reference to a standard California rice straw bale 16 inches wide by 24 inches high by 48 inches long. It will be obvious to those skilled in the art that bales having different dimensions could work equally well with adjustments to certain dimensions of the metal components. The bales  13  are stacked onto foundation wall  12  in an orientation by which the bale length  13 L is aligned with the length of foundation wall  12 ; the height  13 H is a measure of the vertical dimension of the stacked bale; and the width  13 W constitutes the remaining third dimension, which largely determines the thickness of the wall  11 . 
     Referring to  FIGS. 3 ,  4  and  5 , anchor dowels  17  are cast into the concrete foundation wall  12  and extend vertically above the foundation wall approximately the same height  13 H as the bale  13  (see  FIG. 2 ). The anchor dowels  17  terminate in the foundation in a standard hook  17 A and are distributed along the length of the foundation wall  12  in opposing pairs  17 P, with each dowel  17  near one edge of the foundation wall  12 . The dowels  17  of a given pair  17 P are spaced apart a greater distance than the bale width  13 W of bale  13 , and preferably 2 inches to 3 inches greater, so that a bale  13  can readily fit therebetween. Anchor dowel pairs  17 P are set along the length of the foundation wall  12  every 2 feet or 4 feet (when using a 4 foot bale). Whether the spacing is half the bale length  13 L (2 feet) or a full bale length  13 L (4 feet) is dependent on the ultimate size of the wall being built and the conditions of its use. As will become clear from what follows, the choice of spacing (half a bale length or a full bale length) for the anchor dowel pairs  17 P is a choice well within the teachings of the invention. B 2   
     Referring to  FIGS. 4-8 , bracing ladders  21  are secured to the foundation  12  by attachment to an anchor dowel pair  17 P. The ladders  21  are distributed along the foundation  12  at intervals equal to three bale lengths  13 L, or every 12 feet for a 4 foot bale system. Bracing ladders  21  are secured to the foundation by attachment to an anchor dowel pair  17 P by the use of mechanical clamps or the like. The ladders  21  are positioned on the foundation wall  12  so that the plane of the ladders  21  (the plane containing the various parts that make up the ladders  21 ) is transverse to the length  21 L of the foundation  12  and parallel to the ends  13 E of bales  13 . The height of ladders  21  is approximately equal to the height of the wall  11  ( FIG. 1 ) which can be as high as 35 feet. B 3   
     In one embodiment ( FIGS. 6 and 7 ), bracing ladder  21  has a pair of spaced-apart parallel rails  22  rigidly held in place by horizontal connecting struts  23 H and diagonal connecting struts  23 D. The struts  23 H and  23 D not only unify the ladder into a single structural member, but are laid out in a pattern that creates alternating bale windows  24  and bale abutments  26 . The spacing between ladder rails  22  is greater than the bale width  13 W, and the height  24 H of the ladder windows  24  is greater than the height  13 H of the bale  13 . Thus, each ladder window  24  can surround (accommodate) a bale  13  (a bale  13  can pass through a window  24 ). Diagonal ladder struts  23 D provide an abutment for bales  13 , preventing a bale  13  from passing through the ladder at the location of ladder struts  23 D. 
     A foot member  28  at the bottom of each rail  22  provides a fixture for bolting the ladder to the foundation wall  12  as an alternative to, or in addition to, attaching the ladder to an anchor dowel  17 , as described above. The various components of the ladder  21  can either be prefabricated into the constructed ladder  21  and shipped to the building site or constructed on site from small parts. 
     Referring to  FIG. 8 , another preferred embodiment of bracing ladder  21  of the invention is constructed from #4 galvanized rebar. Ladder rails  32  are two spaced-apart lengths of rebar held together by hourglass-shaped struts  33  which have a core cross-member  34  and legs  36  extending vertically from each end of the core cross-member  34 . The connecting struts  33  are also advantageously fabricated from #4 galvanized rebar and affixed to the ladder rails  32  by welding or mechanical clamping means. 
     The struts  33  are spaced along the length of the ladder  21  to form a pattern of alternating bale windows  37  and bale abutments  38 . The hourglass-shaped struts  33  are dimensioned so that the windows  37  are large enough to surround a bale  13  (a bale  13  can pass therethrough), while the abutments  38  prevent bales from passing between the ladder rails  32 . 
     Referring to  FIGS. 2 ,  9  and  10 , once the ladders  21  have been erected and attached to the foundation  12  at the appropriate intervals, bales  13  are stacked onto the foundation with the length  13 L of the bale running in the same direction as the length  12 L of the foundation. It will be understood by those skilled in the art that it is not a requirement of the invention that the bales be placed in this orientation. 
     The bales  13  in the example used here to illustrate the invention are stacked in a running bond in which the bales  13  in a course  13 C (layer or tier of bales) is offset one-half bale length  13 L (2 feet) relative to the bales in the adjacent course  13 C above and below. Thus, the end  13 E of every bale  13  is aligned vertically with the midpoint  13 M of the bale  13  immediately above and the bale  13  immediately below (see  FIG. 9 ). Throughout the description, the pattern just described of stacking the bales  13  with half-length offsets is referred to as a “running bond.” 
     In the preferred embodiment, a bale abutment  38  ( FIG. 8 ) is located at the bottom of each ladder  21  adjacent the foundation  12 . Since the ladders  21  are spaced 12 feet apart (3 bale lengths  13 L), the first course of bales can be laid onto the foundation with the end  13 E of each third bale falling immediately adjacent a ladder abutment  38 . The second course of bales  13  being offset from the course below (as described above) by one-half bale length  13 L, it becomes necessary for a bale to pass through the ladder  21 , which it is able to do by virtue of the placement of ladder windows  37  one bale height ( 13 H) above each bale abutment  38 . Thus, the alternating bale windows  37  and bale abutments  38  of ladder  21  perfectly accommodate the stacking of the bales in a running bond. Furthermore, the intertwining of the bales  13  in the ladders  21  gives the running bond of bales  13  stability. 
     In addition to the above-described bracing ladders  21 , the present invention also utilizes hourglass-shaped bracing spars  41  advantageously constructed from #4 galvanized rebar having a diagonal cross-member  42  and four leg members  43 , one extending generally vertically from the end of each diagonal cross-member  42 . The legs  43  are spaced apart a distance greater than the width  13 W of bale  13 , preferably by 2-3 inches, whereby the leg members  43  can straddle a bale  13  (see  FIG. 9 ). As the bales  13  are stacked, a bracing spar  41  is located at the end  13 E of some of the bales  13 , with the spar legs  43  straddling the approximate midpoint  13 M of the bale above and the bale below. Generally, spars  41  are placed at each bale end  13 E that is vertically aligned with an anchor dowel  17  which typically will be either every end  13 E (where the anchor dowels are at 2 foot spacings) or every other end  13 E (where the anchor dowels are at 4 foot spacings). Spars  41  are not placed at the bale ends  13 E that abut a ladder  21 . The spars  41  are temporarily held in place by the abutment of the adjacent bales, thus, requiring no further securing devices during the stacking process. 
     Referring to  FIG. 10 , five courses  13 C of bales  13  are stacked in a running bond with bracing spars  41  placed between the ends  13 E of all bales  13  (except those abutting a ladder  21 ). Anchor dowels  17  at 2 foot spacings (half a bale length  13 L) along the length of the foundation wall  12  align vertically with the legs  43  of those bracing spars  41  at the same location along the foundation wall  12 . 
     Referring to  FIGS. 11 and 12 , when a stack of bales  13  reaches six courses high (12 feet), it is advantageous to provide horizontal stiffening for additional vertical stabilization. A horizontal stiffening ladder  44  is disposed on top of the sixth course  13 C of bales  13  and attached to the bracing ladders  21  to add stiffness to the pre-membrane wall. Ladder  44  has two spaced-apart parallel ladder rails  46  joined by struts  47  in a triangle pattern. The triangular pattern formed by the struts  47  has well known structural advantages, but other structurally sound patterns could be used. The ladder  44  can be prefabricated and shipped to the building site or can be constructed from smaller parts at the site. 
     The distance between parallel ladder rails  46  of stiffening ladder  44  is preferably just slightly less than the distance between the rails  32  of bracing ladders  21  (see  FIG. 8 ) so that when the stiffening ladders  44  are put in place through bracing ladders  21 , the rails of the two ladders will be close to each other to accommodate making a securing connection between them. The maximum distance between the rails  46  of the stiffening ladder  44 , however, cannot exceed the distance between the rails  32  of bracing ladder  21 . 
     The stiffening ladder  44  can be conveniently constructed from #4 rebar, with the connecting struts  47  welded to the rails  46 . It can alternatively be formed from angle iron members bolted or welded into place. 
     The stiffening ladder  44  is held in place by connection to the bracing ladders  21  by any one of a variety of mechanical means known for tying metal members together, including simple wire twist ties (not shown). 
     For walls greater than 12 feet, it is advantageous to have a stiffening ladder  44  located at the top of the sixth course, or at the approximate mid-height of the wall, whichever is less. 
     Referring to  FIG. 13 , after the stiffening ladder  44  is in place, bales  13  continue to be stacked in a running bond until the full height of the wall is reached. B 4   
     Referring, in addition, to  FIG. 14 , when bales  13  have been stacked to the desired height and spars  41  located, the exposed legs  43  of the spars  41  will be aligned with an anchor dowel  17  in the foundation  12 . A connecting rod  51 , preferably #4 rebar, of a length approximately equal to the height of the wall is secured to each anchor dowel  13  and all of the spar legs  43  aligned with that anchor dowel  17 . Because of the highly flammable nature of straw bale material, it is not advisable to attach the connecting rods to the dowel  17  and spar legs  43  by welding. Any one of numerous well known mechanical clamping mechanisms for securing two lengths of rebar together (such as compression clamp  50 , as shown in  FIG. 15 ) is suitable for attaching the connecting rods  51  to the anchor dowels  17 . While similar clamping mechanisms can be used to attach the spar legs  43  to a connecting rod  51 , connecting them together with simple wire ties  52  (as indicated in  FIG. 16 ) is satisfactory. Once the connecting rods  51  are secured to dowels  17 , spar legs  43  and ladder(s)  44  (if any), a structurally rigid truss system has been constructed that is fully capable of supporting the wall during the application of the membrane  16  (see  FIG. 1 ) without external bracing. 
     Referring to  FIGS. 17 and 18 , a corner ladder  56  can be constructed by securing (as by welding or other connecting means) two mid-wall ladders  21  together at right angles to each other. Once anchored to the foundation  12  by attachment to anchor dowels  17  and plumbed, corner ladders  56  provide a reference and structure by which the mid-wall ladders  21  can be plumbed prior to stacking bales  13 . 
     Referring to  FIGS. 19 and 20 , the membrane  16  is applied to a thickness of approximately 3 inches to fully encase the exposed anchor dowels  17 , spar legs  43  and the connecting rods  51 . All of the metal components within the interior membrane  16  are physically joined to the metal components within the exterior membrane  16  by spars  41  and ladders  21 , creating a wall of exceptional structural integrity. 
     The outstanding structural characteristics of the wall  11 —both before the membrane is applied and after—are largely attributable to the several metal components described in detail above, whereas the bales  13  serve primarily as construction forms, fireproofing and insulation. 
     While the invention has been described and illustrated utilizing a standard California rice straw bale 16 inches wide by 24 inches high by 48 inches long, and various dimensions have been suggested based on that bale size, the invention is capable of fully functioning with bales of different dimensions, in which case, the spacing of the various components of the invention would have to be modified accordingly. While the invention has been described with regard to anchor dowels spaced every 2 feet (half a bale length) along the length of the foundation, under certain conditions and for walls of only moderate height, spacings of 4 feet (one bale length) is adequate. When full-length bale spacing is used for the anchor dowels, it is only necessary to place the hourglass-shaped spars  41  at the head of those bales that align with an anchor dowel. 
     Referring to  FIG. 21 , prior to applying the membrane  16  ( FIG. 1 ), it is advantageous to cover the metal bracing components with welded wire fabric  56 . 
     The foregoing teaches a series of steps for constructing a straw bale core wall onto a foundation wall having vertically extending #4 rebar anchor dowels spaced apart along the foundation wall at 24 inch or 48 inch spacings (assuming use of a standard 4 foot bale length) without external bracing, which steps comprise: 
     (1) Attaching preassembled vertical corner bracing ladders (of rebar or other metal components) to the foundation wall at its corners. 
     (2) Attaching preassembled vertical mid-wall bracing ladders (of rebar or other metal components) between foundation wall corners. 
     (3) Plumbing the corner ladders and intermediate ladders. 
     (4) Stacking straw bales onto the foundation wall in a running bond and installing a cross spar with spar legs at the head of every bale or every other bale, as required. 
     (5) Installing a horizontal preassembled stabilization ladder onto the top of the sixth course of bales (approximately 12 feet) and securing it to the vertical ladders. 
     (6) Stacking straw bales until the final wall height is reached. 
     (7) Adding vertical connecting rods at the location of the spars running from the foundation to the top of the wall. 
     (8) Tying each vertical connecting rod to an anchor dowel protruding from the foundation, as well as the legs of each spar leg in line vertically with the anchor dowel. 
     (9) Covering the bales and metal parts with welded wire fabric and tying it to the vertical connecting rods. 
     (10) Applying a membrane (typically pneumatically placed shotcrete or gunnite) over the bales  13  and internal bracing system  14  that covers the bales and metal components. 
     Of course, various changes, modifications and alterations in the teachings of the present invention may be contemplated by those skilled in the art without departing from the intended spirit and scope thereof. As such, it is intended that the present invention only be limited by the terms of the appended claims.