Abstract:
An insulating concrete form foam block bi-directional system comprises a pair of opposed and parallel foam sidewall panels spaced using a plurality of plastic and metal band ties that act as a fire-break between the two exterior finished concrete wall surfaces. Each tie comprises nearly full sidewall height, plastic flanges which engage the sidewalls and a metal band cross-connecting vertical holders of the ties. The metal band forms a wide opening to enhance concrete flow. The tie results in a minimal downward stress impact on the tie during concrete placement. The top and bottom surfaces of each sidewall are formed with raised areas and non-raised areas which interlock with adjacent blocks. The side surfaces of each sidewall are formed with vertical tongues and grooves which interlock with like tongues and grooves of corner pieces which are adapted to form right or left-hand comers.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0001]     (Not applicable)  
       REFERENCE TO SEQUENTIAL LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON A COMPACT DISC  
       [0002]     (Not applicable)  
       BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     The present invention relates to concrete construction utilizing foam block forms, more specifically to improvements to the foam sidewalls used to create a longitudinally bi-directional system, improved form sidewall spacing ties which create enhanced concrete flow, enhanced strength, and enhanced fire-break properties, and a corner form that can be used as a right-hand or left-hand form.  
         [0005]     2. Description of the Related Art  
         [0006]     Concrete forms made of a polymeric foam material are known. Such forms basically comprise a pair of laterally spaced-apart sidewalls presenting a cavity therebetween. A number of these forms are connected to present longitudinally and vertically aligned cavities for pouring concrete therein.  
         [0007]     One such form is shown in U.S. Pat. No. 3,788,020, issued on Jan. 29, 1974. This patent discloses a concrete form with a pair of sidewalls, end walls and intermediate partition walls. A plurality of these forms are connected to present vertical cavities for pouring concrete therein to form a plurality of vertical concrete columns or piers. These vertical columns are connected by a horizontal concrete beam formed by filling a channel with concrete, the channel presented upon placing one row of concrete forms atop another.  
         [0008]     One problem with existing concrete forms is that the sidewalls must be immobilized so as to resist pressures on the walls during transport and, more importantly, during concrete pouring and curing. If not, the form sidewalls may shift in lateral and/or vertical and/or longitudinal directions. Such displacements make it difficult to easily connect the forms. Also, the forms may separate along the joints respectively presented along the zones of connection between longitudinally and vertically adjacent forms. If the forms are not sufficiently braced, the concrete can cause these joints to separate. The industry refers to such separations as “blow outs”.  
         [0009]     During the pouring of the concrete, a hydraulic concrete load acts on the sidewalls of each form as well as on any structure spanning such sidewalls. The load urges the sidewalls from their proper vertical, lateral and longitudinal spatial relationships. Also, during form transport to the job site, the sidewalls may be displaced due to the weight of other forms stacked thereon. In some cases the distance between the sidewalls may vary. Accordingly, problems will arise when attempting to longitudinally and vertically connect forms as the mating lap joint surfaces and/or tongue/groove elements will not be properly aligned.  
         [0010]     The closest related publications known to the inventor are U.S. Pat. No. 4,223,501 granted to DeLozier Sep. 23, 1980 and Published U.S. Application 2004/0045237 invented by Coombs et al and published Mar. 11, 2004. Each of these publications shows concrete forms made of opposing panels. The panels are held in spaced relationship by ties. In the patent publication, the tie contains inadequate open space to allow for the free flow of concrete necessary during a pouring operation in order to avoid air pockets which will weaken the resulting wall. In both of these publications, the tie is a single piece bent at each side to form an anchor. This allows for lateral movement during shipping and a corresponding loss of alignment. When this happens the units do not fit together properly on the construction site.  
         [0011]     Also, in both of these publications, the tie is made of metal, which conducts heat and can be a mode of transmitting heat during fire. Additionally, in both of these publications there is no predetermined space for connecting the form to studs.  
         [0012]     As seen from the above, various devices in the forms of braces and permanent tension members have been proposed so as to maintain the sidewalls in place to preclude such shifting and/or “blow outs” during concrete pouring and subsequent curing. However, such devices have been relatively complex in construction requiring the sidewalls to have special configurations so as to receive the braces and/or ties and have lacked desirable features.  
         [0013]     In prior art systems, comers present some problems. Typically a wall form is extended to the end of the wall and a piece of foam plastic is secured over the end of the wall form by wire or the like.  
         [0014]     This type of end is difficult to secure to the wall form, frequently breaks during concrete pouring, and is not securely fastened to the wall form. This creates unnecessary labor in fixing breaks, setting up the forms, and affixing exterior sheathing to the corner of the wall.  
         [0015]     In another prior art approach, the specific corner form is provided, but it is preformed for a certain specific job and must be either a right-hand corner or a left-hand corner. Right-hand or left-hand orientation is always determined from a top plan view because these forms have by necessity a top end and a bottom end. Therefore, a right-hand corner form cannot be substituted for a left-hand corner and visa versa. This doubles the number of types of molds required to produce the corner forms, doubles the types of corner forms needed in inventory, increases delivery costs, and so forth.  
         [0016]     Therefore, there is a need for a corner form for a concrete wall that is universal, that is, can be used for either a right-hand or left-hand wall corner; that can be securely and easily attached to the wall form; that does not break during concrete pouring; and that is securely fastened to the wall form.  
       BRIEF SUMMARY OF THE INVENTION  
       [0017]     The present invention is directed to maintaining the positive aspects of the advances already made by the prior art while eliminating the problem areas. Thus, the inventor has invented improvements in concrete forms.  
         [0018]     A particular object of this invention is to provide a concrete form bi-directional system which enhances on-site assembly of the concrete form walls. This improvement takes the form of a bi-directional insulating concrete form system having novel upper, lower, and side surfaces that provide one-hundred eighty degree rotation of the form creating a bi-directional orientation for corresponding insulating concrete forms. Forty-five and ninety degree corner blocks are also part of this invention.  
         [0019]     One improvement disclosed in this invention is a corner form for a concrete wall. This form creates a universal corner form, that is, it can be used to create right-hand or left-hand wall corners in concrete walls. Another feature of this corner form is that it can be securely and easily attached to the wall form. Another feature of this corner form is that it can provide a corner form for a concrete wall that does not break during concrete pouring. This corner form for a concrete wall is securely fastened to the wall form.  
         [0020]     Another improvement over the prior art is a form tie, more particularly, novel form ties for maintaining the sidewalls of a concrete form in desired longitudinal, vertical and laterally spaced-apart relationships that also serve as a fire-break. Each form tie generally comprises a pair of plastic vertical side pieces with a pair of metal horizontal pieces spanning the form sidewalls. The ties are formed by connecting a pair of plastic vertical side pieces with a pair of metal horizontal pieces. The horizontal pieces are located at the upper and lower ends of the vertical pieces. The vertical side pieces are embedded in the sidewalls of the forms during the molding process with the horizontal pieces spanning the facing interior surfaces of the sidewalls. The ties preclude lateral, vertical and longitudinal shifting of the sidewalls during transport and use. The ties of the present invention find use in concrete forms and effectively interface with the form sidewalls so as to maintain the walls in a desired spatial relationship during transport as well as concrete pouring and curing. The forms of the present invention also automatically present a longitudinally enhanced fire-break resulting from the innovative use of metal band horizontal pieces and thermoplastic vertical side pieces. During a fire, the thermoplastic vertical side pieces melt and do not conduct heat to the horizontal pieces. Thus, the heat stays on one side of the enclosed concrete. Also, the ties are oriented to reduce downward stress on the ties, as a whole, during the pouring of plastic concrete in the cavity formed between the sidewalls.  
         [0021]     The ties resist loads that impart tension, compression, bending, twisting and lateral stresses acting thereon. The ties also diminish the lateral, vertical and longitudinal displacement of adjacent sidewalls of a concrete form during transport and use. The ties of the present invention further enhance on-site assembly of the concrete forms, inclusive of the installation of exterior finish materials attached thereto. These ties effectively resist the forces arising from concrete flow but without interference with the concrete flow in the cavity between the form sidewalls and between adjacent forms.  
         [0022]     Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, now preferred embodiments of this invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]      FIG. 1  is an elevational perspective view of an elongated concrete form of the present invention.  
         [0024]      FIG. 2  is an elevational top view of the elongated form shown in  FIG. 1 .  
         [0025]      FIG. 3  is an elevational perspective view of one embodiment of an elongated form sidewall of this invention.  
         [0026]      FIG. 4  is an elevational end view of the elongated form sidewall of  FIG. 3 .  
         [0027]      FIG. 5  is an elevational top view of the elongated form sidewall of  FIG. 3 .  
         [0028]      FIG. 6  is an elevational side view showing the inside of the elongated form sidewall of  FIG. 3 .  
         [0029]      FIG. 7  is an elevational perspective view of another embodiment of an elongated form sidewall of this invention.  
         [0030]      FIG. 8  is an elevational end view of the elongated form sidewall of  FIG. 7 .  
         [0031]      FIG. 9  is an elevational top view of the elongated form sidewall of  FIG. 7 .  
         [0032]      FIG. 10  is an elevational side view of the elongated form sidewall of  FIG. 7 .  
         [0033]      FIG. 11  is an elevational end view of an elongated form of this invention.  
         [0034]      FIG. 12  is an elevational perspective view of a part of an elongated form sidewall showing a male connection.  
         [0035]      FIG. 13  is an elevational perspective view of a part of an elongated form sidewall showing a female connection.  
         [0036]      FIG. 14  is an elevational perspective view of an elongated form of the present invention showing the contours of the form.  
         [0037]      FIG. 15  is an elevational top view showing a corner form of this invention in place.  
         [0038]      FIG. 16  is an enlarged elevational top view of a portion of a first sidewall shown in  FIG. 15 , showing the male connection in detail.  
         [0039]      FIG. 17  is an enlarged elevational top view of a portion of a second sidewall shown in  FIG. 15 , showing the female connection in detail.  
         [0040]      FIG. 18  is an elevational perspective view of a corner form of this invention.  
         [0041]      FIG. 19  is an enlarged detail view of the corner of the form of  FIG. 18 .  
         [0042]      FIG. 20  is an elevational side view of the open side of the form of  FIG. 15 .  
         [0043]      FIG. 21  is an elevational side view of the closed side of the form of  FIG. 15 .  
         [0044]      FIG. 22  is an elevational side view of the form of  FIG. 15  from the right end of the form.  
         [0045]      FIG. 23  is an enlarged detail view showing the top end of the form as seen in  FIG. 22 .  
         [0046]      FIG. 24  is an enlarged detail view showing the bottom end of the form as seen in  FIG. 22 .  
         [0047]      FIG. 25  is an elevational top view of a corner form sidewall of this invention.  
         [0048]      FIG. 26  is an enlarged elevational top view showing the male edge of the form sidewall of  FIG. 25 .  
         [0049]      FIG. 27  is an enlarged elevational top view showing the female edge of the form sidewall of  FIG. 25 .  
         [0050]      FIG. 28  is an elevational perspective view of a corner form sidewall of the present invention.  
         [0051]      FIG. 29  is an enlarged elevational perspective view showing the top corner of the corner form sidewall of the present invention.  
         [0052]      FIG. 30  is an elevational side view of a corner form sidewall of this invention.  
         [0053]      FIG. 31  is an enlarged side elevational view of the top portion of the corner form sidewall shown in  FIG. 30 .  
         [0054]      FIG. 32  is an enlarged elevational side view of the bottom portion of the corner form sidewall shown in  FIG. 30 .  
         [0055]      FIG. 33  is an elevational side view of a first corner sidewall section for a form of this invention.  
         [0056]      FIG. 34  is an enlarged elevational side view of the top end of the section of  FIG. 33  showing detail.  
         [0057]      FIG. 35  is an enlarged elevational side view of the bottom end of the section of  FIG. 33  showing detail.  
         [0058]      FIG. 36  is an elevational end view of a corner sidewall of this invention.  
         [0059]      FIG. 37  is an enlarged elevational end view of the corner shown in  FIG. 36  showing detail.  
         [0060]      FIG. 38  is an elevational perspective view of a corner sidewall.  
         [0061]      FIG. 39  is an elevational perspective view of a top corner section of a corner sidewall shown in  FIG. 38  showing detail.  
         [0062]      FIG. 40  is an elevational top view of a corner sidewall of this invention.  
         [0063]      FIG. 41  is an elevational top view of a first end of the corner sidewall of  FIG. 40  showing detail.  
         [0064]      FIG. 42  is an elevational top view of a second end of the corner sidewall of  FIG. 40  showing detail.  
         [0065]      FIG. 43  is an elevational side view of a tie of the present invention  
         [0066]      FIG. 44  is an elevational front view of a tie of the present invention  
         [0067]      FIG. 45  is an elevational perspective view of a tie of the present invention.  
         [0068]      FIG. 46  is a top cross-sectional view of a form of one embodiment having ties attached thereto.  
         [0069]      FIG. 47  is a front cross-sectional view of a form of one embodiment having ties attached thereto.  
         [0070]      FIG. 48  is an end cross-sectional view of a pair of concrete form sidewalls of this invention having ties attached thereto.  
         [0071]      FIG. 49  is an elevational perspective view of a sidewall of one embodiment of this invention having ties attached thereto.  
         [0072]      FIG. 50  is an elevational perspective view of a wall using the forms of this invention under construction.  
         [0073]      FIG. 51  is an elevational perspective view showing the placement of a bottom layer of forms in a wall.  
         [0074]      FIGS. 52 and 53  are cross-sectional views of the forms of this invention having rebars passing through poured concrete and inner and outer finishing. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0075]     The invention will now be described with reference to the above drawings wherein like reference numerals refer to like parts throughout the description.  
         [0076]     Turning more particularly to the drawings,  FIGS. 1-14 , show one type of longitudinal concrete form  2  which comprises a pair of rectangular sidewalls  4 . These sidewalls  4  are preferably made of fire-resistant foamed plastic. Each sidewall  4  has upper  6  and lower  8  longitudinal surfaces as well as a pair of opposed vertical surfaces  10 . Each sidewall  4  has an inner surface  12  and an outer surface  14 . When the longitudinal form  2  is assembled, the inner surfaces  12  of the sidewalls  4  cooperate to form a plurality of vertical cavities  16  and a vertical slot  18 . The slot  18  longitudinally spans the length of the form  2  and connects the cavities  16 . The outer surface  14  is flat and serves to receive facing or studs.  
         [0077]     As shown best in  FIG. 11 , each sidewall  4 ′,  4 ″ has a raised portion  20  and a non-raised portion  22  along the upper surface  6  which mate with a complementary non-raised portion  22  and raised  20  portion located along the lower surface  8  of an overlying form  2 . In each sidewall  4 ′  4 ″, the vertical surfaces  10 ′,  10 ″ as shown best in  FIG. 2  are made up of a tongue  24  and groove  26 . For a first (outer) sidewall  4 ′, a first vertical surface  10 ′ has a tongue  24  and the second vertical surface  10 ″ has a corresponding groove  26 . For the second (inner) sidewall  4 ″ of a form  2 , the sidewall  4 ″ opposite the first sidewall  4 ′, the first vertical surface  10 ′ has a groove  26  and the second vertical surface  10 ″ has a tongue  24  as best seen in  FIGS. 12 and 13 . Accordingly, the forms  2  may be connected in longitudinally extending courses and stacked one atop the other. In the above, “outer” and “inner” are related to the exterior or interior of the building. This is best shown in  FIGS. 50 and 51 .  
         [0078]     Referring to  FIGS. 50 and 51 , the first course of longitudinal forms  2  is positioned atop a footing  28  and held in place by various materials such as plastic roof cement. It is understood that other types of connection of the first row of longitudinal forms  2  to the footing  28  may be utilized, such as placing the forms  2  in a wet footing  28  and allowing the footing  28  to subsequently dry. Upon reaching a desired height of the forms  2 , wet concrete is poured between the form sidewalls  4 . From  FIG. 50 , it is seen that the forms  2  are staggered among rows so as to preclude formation of a continuous vertical joint among the form rows. The poured concrete fills the vertical cavities  16  and longitudinally extending vertical slot  18  of each form  2 . Also, upon stacking a second course of forms  2  atop the first course of forms  2 , a horizontal channel is formed which spans the upper and lower forms  2 . The poured concrete will fill the channel of the form  2 . Thus, a concrete wall within the interior of the forms  2  is presented. The forms  2  are left in place for insulating the resulting concrete wall. Wall clips (not shown) may be used for attaching exterior siding thereto. Such clips are the subject of a separate patent application by the inventor.  
         [0079]     It is known that the courses of the forms  2  may be selectively configured so as to present walls of various configurations. Also, door frames, window frames, bucks, bulkheads, and the like may interrupt the courses of forms  2  so as to provide openings for insertion of doors, windows and the like therein while precluding spillage of poured concrete from the forms  2 .  
         [0080]     Referring to  FIGS. 15-42 , corner forms  30  of this invention will be described. There is shown a universal corner form  30  for concrete walls. By universal corner form  30 , it is intended to mean that there is an open left-hand side  32  of the corner form  30  or an open right-hand side  34  which can fit onto either end of the forms  2  of the present invention.  
         [0081]     As can best be seen in  FIGS. 15-17 , the vertical surfaces  36  of the corner form  30  are the same as the vertical surfaces  10  of the sidewall forms  2 . Also, the upper  6  and lower  8  longitudinal surfaces of the corner pieces  30  are configured identically to the upper  6  and lower  8  surfaces of the sidewall forms  2 .  
         [0082]     With reference to the sidewall form  2  shown in  FIG. 14 , it may be assumed that the sidewall  4  which has the tongue  24  on the vertical surface  10  is the outer sidewall  4 ′ while the sidewall  4  which has the groove  26  on the vertical surface  10  is the inner sidewall  4 ″.  
         [0083]     In order to make a left corner using the above form, the open right-hand side  34  of the corner form  30  as shown in  FIG. 15  is connected to the above form  2 . Similar straight forms  2  may then be connected to the open left-hand side  32  of the corner form  30 . In such an arrangement, the upper longitudinal surface  6  of both the straight forms  2  and the corner forms  30  will contain raised portions  20  along the outer surface  14  and non-raised portions  22  along the inner surfaces  12 .  
         [0084]     In a like manner, to form a right corner using the above corner form  30 , the open left-hand side  32  of the corner form  30  shown in  FIG. 15  is connected to the above straight form  2 . Again, straight forms  2  may be connected to the free end of the corner form  30 . In such an arrangement, the upper longitudinal surface  6  of both the sidewalls  4  and the corner pieces will contain raised portions  20  along the outer surface  14  and non-raised portions  22  along the inner surfaces  12 .  
         [0085]     Should the straight form  2  be in place such that the outer sidewall  4 ′ contains an upper longitudinal surface  6  having a raised portion  20  along inner surface  12  and a non-raised portion  22  along the outer surface  14 , the corner form  30  may simply be turned over so that the former upper longitudinal surface  6  is now the lower longitudinal surface  8 . The corner form  30  will then have an outer sidewall  4 ′ which contains an upper longitudinal surface  6  having a raised portion  20  along inner surface  12  and a non-raised portion  22  along the outer surface  14 . This allows the corner form  30  of the present invention to be a universal corner form as it can form a left corner or right corner regardless of the configuration of the vertical surfaces of the sidewalls  4  of the form  2 .  
         [0086]     Referring to  FIGS. 43-49 , the ties  38  of this invention are described. Each tie  38  presents an overall square or rectangular configuration. The tie  38  comprises first and second laterally spaced-apart vertical thermoplastic side pieces  40  with two connecting metal horizontal pieces  42  therebetween.  
         [0087]     Each side piece  40  generally comprises a vertical holder  44  having a proximal edge  46  and a distal edge  48 . The proximal edge  46  is of lesser length than the distal edge  48 . The vertical holder  44  contains a plurality of holes  50  to allow the passage of polystyrene beads and to avoid the buildup of air pockets in the vicinity of the tie  38 . The side piece  40  contains a vertical flange  52  laterally displaced from each side of the proximal edge  46  of the vertical holder  44 . The presence of two flanges  52  gives added dimensional stability and strength to the prepared form  2 .  
         [0088]     A horizontal piece  42  in the form of a thin metal band extends between approximately the midline between the proximal edge  46  and the distal edge  48  of a first vertical holder  44  and approximately the corresponding midline of a second vertical holder  44  at the lower ends  54  thereof. Likewise, upper ends  56  of first and second vertical holders  44  are similarly joined by a metal horizontal piece  42 . The horizontal pieces  42  may be secured to the vertical holders  44  by common fastening devices, preferably rivets. Dimensional stability may be assured by having the horizontal pieces  42  fit into grooves  58  in the vertical holders  44 . Complimentary notches  60  and protrusions  62  in the horizontal pieces  42  and the vertical holders  44  serve to increase lateral and vertical dimensional stability of the tie  38  and any form  2  containing the tie  38 . The thin metal band horizontal piece  42  is located such that the upper  64  and lower surfaces  66  are narrow and the two side surfaces  68  are wide.  
         [0089]     In the event of a fire on a first side of a concrete wall prepared using the ties  38  and forms  2  of the present invention, the thermoplastic side pieces  40  melt and cannot transfer sufficient heat to the metal horizontal pieces  42  to allow the fire to spread to the opposite side of the concrete wall.  
         [0090]     As is known in the prior art, two bipartite molds are used for forming the sidewalls of the polymeric concrete form. Polystyrene beads are blown into the respective sidewall molds at a first temperature with the beads expanding upon cooling so as to fill the mold. Upon the beads being reheated at an elevated temperature, a second expansion occurs so that the foam fills the mold. Upon removal of the mold the sidewalls  4  are presented.  
         [0091]     One problem which has arisen with the use of form ties is that the sidewall molds must have openings therein to allow for insertion of the ends of the tie in each mold and extension of the tie between the sidewall molds. In turn, the expanding foam may escape from these mold openings. Such a leakage/seepage of the foam from the mold may impair form integrity and lead to undesirable ruptures, cracks, etc. in the forms. Such defects may not be visibly apparent until the form sidewalls are subjected to the hydraulic loads presented by the poured concrete between the form sidewalls.  
         [0092]     In response to such a problem, the vertical side pieces  40  of the ties  38  of this invention are configured to seal the mold openings. The forms  2  are prepared as a unit with the ties  38  being embedded in the sidewalls  4 . Thus, the vertical side pieces  40  preclude escape of the expanding polystyrene foam from the mold. Also, the distance between these vertical side pieces  40  defines the length of the horizontal pieces  42  and thus the resulting lateral displacement between the sidewalls  4 . Accordingly, the coplanar relationship of the opposed, interior surfaces  12  of the sidewalls  4  presents a visual gauge of a common lateral displacement between the sidewalls  4  of the forms  2 .  
         [0093]     Thus, the horizontal pieces  42  fix and maintain a desired lateral distance between the interior surfaces  12  of the sidewalls  4  of the form  2 . This common lateral modularity assures the builder that the stacked forms will present even exterior surfaces  
         [0094]     As best shown in  FIGS. 46-49 , the ties  38  are embedded in the sidewalls  4  of the form  2 . As such, they resist any forces acting thereon which may disrupt the monolithic structure of the sidewall  4 . The horizontal pieces  42  span the sidewalls  4 . As such, a plurality of horizontal pieces extends between the sidewalls  4  so as to maintain the distance therebetween in the presence of hydraulic concrete loads. It is noted that the horizontal pieces  42  are so arranged as to present a minimal amount of surface to a longitudinal concrete flow through the form  2 .  
         [0095]     The ties  38 , as above described, resist tension, compression, bending, twisting and lateral forces acting thereon during transport as well as during concrete pouring and curing.  
         [0096]     Thus, longitudinal shifting of the sidewalls  4  of the form  2  is particularly precluded. Such preclusion also contributes to the elimination or reduction in the width modularity during form use.  
         [0097]     Referring to  FIGS. 52 and 53 , following construction of the form wall and prior to the pouring of the concrete, horizontal rebars  70  are placed on the upper surface  64  of one lower horizontal piece  42  and the corresponding surface  64  of the other lower horizontal pieces  42  of the ties  38 . Following the installation of horizontal rebars  70 , vertical rebars  72  are installed offset from the center of the form  2  to lend support to the concrete wall. Following the installation of vertical rebars  72 , the vertical  72  and horizontal  70  rebars are tied into place.  
         [0098]     As best seen in  FIGS. 3-10 , some of the inner sidewalls  4 ″ contain notches  96  on the upper longitudinal surface  6  thereof. These notches  96  may hold the short side of L-shaped pieces (not shown). The long side of such pieces will fit against the outer surface  14  of the sidewalls  4 . The configuration of the short side of the L-shaped piece is such that it completely fills the notch  96 . The configuration of the long side of the L-shaped piece is such that it will lie flat along the outer surface  14  of the inner sidewall  4 ″. The long side presents a solid surface to aid in nailing studs to the inner sidewall  4 ″. To this end, the distance between the notches  96  is equal to the conventional distance between studs.  
         [0099]     It is to be understood that while certain forms of this invention and dimensions have been illustrated and described, the invention is not limited thereto except insofar as such limitations are included in the following claims and allowable functional equivalents thereof.