METHOD AND APPARATUS FOR CONSTRUCTING RAMMED EARTH WALLS WITH INTEGRAL RENDER

Abstract: A method for constructing render jacketed, rammed earth walls for buildings which utilizes a rectangular container (10) which functions as a mould and also a hopper and skip, the container has an open top and a bottom closable by two half trapdoors (15a, 15b), maintained in inclined closed position up from the bottom by cam trapdoor-retaining bars (17, 18) releasable by hand pull rods (19, 20) attached to retainer chains (23, 24); the container (10) is removably carried with trapdoors (15a, 15b) closed upon a rubber-tyred, wheeled, ground level trolley (58) during level-filling with loose earth; two, three-sided trays (27, 28) of lateral dimensions substantially equal to those of the container (10) are level-filled with a powdered cement/sand render mix of low moisture content and stacked upon the container (10), each end (13, 14) of which is provided with a pair of pivot brackets (35, 36, 39, 40) of unequal length which respectively have a hole (37, 38) for detachable fixture of render trays (27, 28) to the container (10); the filled container (10) and trays (27, 28) are lifted by a hoist (55) and lowered into a wall mould formwork of plywood panels (62, 50), the external, lateral dimensions of the container (10) being sufficiently less than the internal dimensions of the formwork to create outer or veneer moulding cavities. When the container (10) rests upon a concrete footing (49), or previously rammed earth layer, the trays (27, 28) are tipped in mutually opposite directions in a vertical arc to put the loose render into the veneer mould cavities between formwork members (62, 50) and the container (10); the trapdoors (15a, 15b) are opened by undoing chains (23, 24), then freeing retainer rods (19, 20) to allow cam retainer bars (17, 18) to fall, the trapdoors (15a, 15b) opening under the weight of loose earth, the container (10) is lifted and loose earth pours out between outer render layers (68, 69) which are rammed simultaneously with the earth as a core (67) to obtain a rammed earth, render jacketed, integral mass.

Description: METHOD AND APPARATUS FOR CONSTRUCTING RAMMED EARTH WALLS WITH INTEGRAL RENDER This invention relates generally to methods of building construction using materials, such as mud bricks, earth, soil and the like and unskilled labour amd more specifically is concerned with the construction of walls for homes by owners using loose earth, taken from owner builder sites, or elsewhere and then rammed. The invention, according to one broad concept resides in apparatus for forming rammed earth walls for building structures which includes two side and two stop end wood plank or board formwork members, placed in parallel spaced relationship and clamped together to form a wall moulding cavity for rammed earth, placed within the cavity, a bucket or the like for filling with rammed earth and lift means for lifting the earth-laden bucket up to the level of formwork members and a ram for ramming the earth into the formwork cavity characterized in that: a wall spacer member is provided at a distance from the inner surface of at least one formwork member which is less than the total width between an opposite formwork member to form an inner mould wall cavity for rammed earth and one or two outer mould cavities for moist, powdered cement render, the render being rammed as an outer layer or layers of facing or veneer jacket simultaneously with earth rammed in the inner or central cavity, whereby the render veneer becomes an integral moulded jacket with the rammed earth wall. Preferably, two spacers are used to form a central moulding cavity for a rammed earth core and two other cavities for outer layers of rammed powdered render or veneer material, the total width of the two outer moulding cavities being less than the width of the central moulding cavity, the height of the spacers being equal and enabling the height of the render or veneer jacket to be equal to, or greater than the height of earth rammed in the central moulding cavity and more preferably, there are two spacers formed into the side walls of a box-like container which functions as a hopper/skip having side walls and end walls with lateral dimensions less than those of formwork, the hopper/skip container having an open top with a screening grid and a closable bottom or floor and is adapted to be level-filled with loose earth with the bottom closed and with the container resting upon the foundation footings, or upon a layer of previously rammed and render veneered earth in formwork in a wall structure a pair of rectangular, flat, three-walled trays is adapted to be placed upon the loose-earth filled container and the trays level-filled with a moist powder, cement render mix, the trays are tipped in opposite mutual directions into cavities between the formwork panels and the side walls of the container, until the level of render is slightly above that of the earth, the bottom of the tray preferably comprises dual trapdoor segments, opened manually by lift and drop rods fastened by brackets and the container has hoist attachment lift means thereon for lifting up the container allowing earth to fall out and fill the wall cavity between the loose render material, both render and earth then being rammed into an integral mass after the container is lifted out of the way. According to one form of the hopper/skip, which may be preferred, the openable bottom thereof comprises a dual segment trapdoor, centrally hinged at a distance above the level of the bottom of the hopper walls and inclined at an angle to the horizontal and vertical, when in a fully closed position and when in a partially open position. The invention, according to another broad concept resides in a method for constructing integral rammed earth and render walls for buildings, homes and the like which comprises placing side wall and stop end vertical timber formwork members upon a wall foundation and in parallel arrangement to form a wall unit mould cavity for filling with loose earth, reducing the width of the cavity by placing a wall spacer member or members therein at a distance from the inner surface of at least one form- work member to form an inner mould wall cavity for rammed earth and one or two outer mould cavities for render, progressively filling and ramming the inner cavity with earth fill material while simultaneously filling and ramming at least one outer cavity with damp particulate veneer or facing render material to provide a smooth aesthetically acceptable and weather-sealing, external or internal, or both external and internal facing or veneer finish to the exposed surfaces of the rammed earth wall unit. More particularly and preferably, each spacer is formed as an open-top, straight-walled, square or rectan¬ gular hopper container serving as a hopper/skip with walls which are of lesser lateral dimension than formworks, an openable bottom or floor which is, when closed, adapted to be filled up with earth then lifted up above the form- work and then lowered into the wall cavity for bottom discharge into the central wall cavity, the side cavity or cavities being filled with moist powdered cement render material, both earth and render being compressed while being rammed into the cavities, the cement render prefer¬ ably being carried on top of the hopper/skip in tra'ys which are tiltable with respect to the hopper/skip, the render being transferable from the trays into the side cavities alongside the earth and adapted to be rammed simultaneously with the earth. The advantages of the rammed earth walls with integral rammed render of the invention are that the render is easier and quicker to apply without requirement for skilled labour and the finished render surface is smooth enough to receive wall paper on internal walls, or paint directly without prior preparation and sealing and is also high enough in density to eliminate the need for sealing against the weather. Advantageously, it is possible to use a wide variety of earth and soil types and since the render can be wedged into the wall earth structure, it is less likely to separate as with conven- tional render. The integral rammed render is applied in a semi-dry low moisture content state and is stronger and denser than conventional render which is applied in a wet slurry and is weaker amd more porous after curing. A non-limitative example of a practical arrange¬ ment of the invention will now be described with reference to the accompanying drawings in whicht Figure 1 is a perspective view of a rammed earth wall forming and render facing hopper/skip apparatus, constructed in accordance with the invention. Figure 2 is an end elevation of the apparatus of Figure 1 in situ between formwork and on foundation footings for a rammed earth wall shown in vertical cross- section. Figure 3 is a scrap perspective of hopper/skip, optional, variable width arrangement. Figure 4 is a schematic end view, similar to Figure 2. Figure 5 is a partial, typical, vertical cross- section through a wall constructed in accordance with the invention. Figure 6 is a perspective view of apparatus ■ . of the invention on a building site. Referring to the drawings, there is shown in Figure 1, apparatus for progressively applying a structurally strengthening, aesthetic and protective facing or rendering simultaneously on both inner or outer wall surfaces of a rammed earth building wall structure, the apparatus comprising a hopper/skip 10, adapted to be level-filled with moist earth preferably of 10% moisture content - an ideal soil being about 60% sand and 40% clay. Organic top soil matter is unsuitable and must not be usedfor rammed earth wall construction. The tray is preferably in the form of an elongate metal box with side walls 11, 12, end walls 13, 14 and with an open top having a grid 14a and a bottom which is openable and closable by a trapdoor 15, split into two longitudinal segments 15a, 15b, (shown in fully open, earth dropping, vertical position in Figure 1), the top or inner edges thereof being hingedly mounted along the trapdoor support bar 16 which in turn is mounted along the longitudinal centre line of the hopper/skip at a vertical distance above the bottom line. In Figure 4, the trapdoor segments 15a, 15b, shown in an inclined, fully closed, earth-retaining position, the radial distance or width of the trapdoor segments being such as to allow the segments to partially drop down in contact with the top surface of a foundation layer or previously rammed layer to allow loose earth to fall and form starting side portions of earth. The trapdoor segments 15a, 15b are also designed to be retained in an inclined, fully closed position by means of tilting cam bars 17, 18, pivotally mounted upon and extending longitudinally along the inside of the side walls at a distance from the bottom edge thereof. The cam bars 17, 18 are retained in lifted up position underneath the outer edges of the trapdoors by means of the rods 19, 20, the lower ends of the rods being pivotally attached to the cam bars while the upper ends each have a bolt head adapted to be placed over the slotted retainer brackets 21, 22. The rods are movable both laterally and vertically, as shown by the arrows and each has a retaining chain 23, 24, the end link of each chain being adapted to be retained upon a retaining spike 25, 26. Two, three-sided, tiltable trays 27, 28 are adapted to be level-filled with moist (5% to 15% and preferably 10% water), powdered cement render mixture (1:5 cement/sand ratio) by placing the trays in juxta¬ position upon the groundwit.h open (non-walled) sides facing in abutment and then level-filling the trays which are then stacked upon the hopper/skip, each tray has two pivot pins 29, 30, 31, 32, protruding from each end thereof, the pins being adapted to be placed respectively into grooves 33, 34 of brackets 35, 36, or holes 37, 38 of brackets 39 40 at each end of the hopper/skip. The brackets of one side are of different height than those of the other side to enable the stacked trays to be tilted successively, each in a vertical arc in an opposite direction to transfer loose, moist powdered cement render_fτ:om each tray into a separate render moulding cavity, approximately 30mm wide, as shown in Figure 4 of the drawings. The hopper/skip has two vertical suspension bars 41, 42, upstanding therefrom with a strengthening spacer bar 43 extending therebetween. At the top of each suspension bar, there is provided a hole for attachment of hooks of the lifting chain (or cable) 44, for lifting by a hoist (or a block and tackle) _ described later with reference to Figure 6 of the drawings. There is provided on each end wall of the hopper/skip 10, two pairs of freely rotatable guide members or wheels, such as the two shown 45, 46 and these wheels are adapted to help guide and maintain the hopper/skip in a horizontal position within a cavity between already formed walls and formwork as shown in Figure 6. Referring to Figure 3, there is shown an end wall structure of the hopper/skip which is 240mm in height, whereby the width may be varied from 240 to 290mm in accordance with different wall thickness requirements. In a similar manner, the length may also be varied from 1200mm to 1900 ~ jam. In the arrangement shown in Figure 3, each side wall panel is turned at right angles to form overlapping end wall panels and inner and outer full height and width strengthening/joining panel 47, 48 are bolted over the turned-in end wall segments. Refering to Figures 2, 4 and 5 which illustrate the method of constructing an integral rammed earth wall and render structure, there is shown in Figure 2, the hopper/skip 10 of the invention, level-filled with earth together with the two stacked trays 27, 28, thereupon level-filled with powdered cement render (cement/sand mix of 10% moisture content) are lowered into the wall cavity, placed upon concrete footings 49 (Fig. 2, or rammed earth Fig. 4) and between plywood formwork members 50, 51. Damp course 49a is preferably included as in Figure 4. Each tray is tilted in a single, mutually opposite direction to onload moist cement render powder into wall outer cavities 52, 53. At this stage with the render in position, the trapdoor segments are allowed to drop down by loosening the chains and also the cam rods 19, 20 by hand from the brackets into a partially inclined, initial unloading postion to allow some earth to fall downwards and initially outwards, towards the cement render cavity while still retained by the sidewalls. Referring to Figure 6, the hopper/skip is then raised by the hoist chain or cable 54 by operating the hoist 55 (or block and tackle) whereupon the trapdoor segments drop to a vertical, fully-open position to release the remainder of the loose earth from the hopper/skip after which the hopper/skip carrying the trays is lowered to the ground outside of the formwork and onto the rubber-tyred, wheeled, hand trolley. Both the outer layers of cement render powder and the earth are compacted together.by ramming either manually or mechanically to form an integral, continuous 350mm thick wall. Vertical wall conduit cavities comprising continuous cavity 59 and interrupted cavities 60 are formed in the end face 61 of wall sections by angle-iron inserts in formwork stop ends. These cavities can be used for keying adjacent panels. Anchorages can also be embedded in wall structures. The formwork shown in Figure 6, comprises a full height rear panel 62 formed in two sections, the front being formed of stacked single layer sections for access, such as that designated 50. It will be appreciated that, instead of using the trays, the cement render mix can be poured into the outer cavities by pumping with a hose, or by mechanical shovels or the like. After each wall is completed, the whole gantry is moved to the next wall section to be constructed by by means of wheels 63 on tracks 64. A preferred method of constructing the wall is shown in Figure 5 of the drawings which shows a section of rammed earth wall, including steel or wire mesh, such as chicken wire reinforcement and wall ties 65 , 66, placed between alternate layers of a rammed earth core 67 and outer integral rammed, moist, powdered cement render jacket or facings 68, 69. It will be noted that there are protrusions of render, such as those designated 70, 71 into the rammed earth. This effect creates improved bonding between render and earth and is achieved by having the height of the render above the height of the earth, when the render is poured from the trays into the cavity between formwork and the hopper/skip.

Claims: rece ved by the International Bureau on 7 June 1988 (07.06.88); original claims 21-24 amended; new claims 25-27 added (3 pages)] 17. Apparatus according to any preceding claim wherein the hopper/skip incorporates a screening grid along the top thereof. 18. Apparatus according to any one of claims 4 to 17 which includes a wheeled hand trolley (58) of rectangular form for transporting the hopper/skip along the ground at a building site. 19. Apparatus according to any preceding claim which includes a hoist gantry mounted on wheels adapted to run on ground tracks to move the hopper/skip parallel to formwork. 20. Apparatus according to any preceding claim wherein the gantry supports a wheeled hoist carriage upon tracks for moving the hopper/skip transverse to wall formwork. 21. Apparatus according to any preceding claim wherein the hopper/skip includes at least one guide member project¬ ing from along the vertical centre-line of each end wall (13, 14) thereof, each guide member being adapted to be placed within a respective pair of vertical guide rail rail members (59, 60) fixed to the inner or mould cavity side of each end stop members, the arrangement being such as to enable centering of the hopper/skip in all lateral directions . 22. Apparatus according to claim 21, wherein there are two guide members in mutual vertical alignment in each end wall. 23. Apparatus according to claim 21 or 22, wherein the two guide members are each freely rotatable wheels (45, 46) which are adapted to be rolled up and down the formwork in a gap between angle iron guide rail members (59, 60) fixed to the stop end members (61, 61a). 24. Apparatus according to any one of claims 21 to 23 wherein when the stop end formwork members (61, 61a) are removed with the guide rails fixed thereto and after form¬ ation of the rammed earth, render-jacketed wall, the guide rails form ''cavities for conduits, tie rods or the like. 25. A method for constructing integral rammed earth and render-jacketed walls for buildings, homes and the like which comprises placing side wall and stop end formwork vertical timber formwork members upon a wall foundation and in parallel arrangement to form a wall unit mould cavity for filling with loose earth, reducing the width of the cavity by placing a wall spacer member or members therein at a distance from the inner surface of at least one formwork member which is less than the total width between opposite formwork member to form an inner mould cavity for rammed earth and one or two outer mould cavities for render, filling the inner cavity with earth fill material, while simultaneously filling at least one outer cavity with damp particulate veneer or facing render material, simultaneously ramming earth and render to provide a smooth aesthetically acceptable and weather-sealing, external or internal, or both external and internal facing or veneer finish to the exposed surfaces of the rammed earth wall. 26. A method according to claim 21, wherein ' there are two spacers which form a render veneer moulding cavity on each side of an earth moulding cavity, the spacers being formed by side walls of an open-top, straight-walled, rectangular container having an open, but closeable bottom, the hopper/skip container being of lesser dimensions than the formwork, the method comprising level-filling the hopper/skip comtainer with loose moist earth outside of the formwork, level-filling two tiltable cement render carrying trays and then placing said trays onto the hopper/skip container outside of the formwork, lifting the container and trays over a formwork wall cavity, lowering the container into the formwork with the container equally, laterally spaced from the formwork and when the container is in contact with footings, or a rammed earth/veneer render layer tipping the trays to fill wall outer cavities with then after the outer cavities .are filled, opening the bottom of the container to allow earth to fall out and raising the trays and container out of the wall cavity and simultaneously ramming the loose, moist earth and both layers of moist, powdered render material to obtain an integrated veneer, rendered earth wall mass. 27. A method according to claims 25 and 26, wherein the loose moist, powdered render material is poured into the wall outer mould cavities, up to a height which is greater than the level of loose earth, so that the render is partially folded-over onto the earth, when the earth is rammed.

Inventors: NOVOTNY JAN, NOVOTNY, JAN
Applicants: NOVOTNY JAN, NOVOTNY, JAN
Application year: 1988
Main classification: E04B2
IPC codes: E04B2, E04G11