WO2014115003A1 - A construction method and system for constructing a wall of a building structure - Google Patents

Abstract

A method of constructing a wall of a building structure includes erecting a temporary support structure 14 on a ground surface and stacking elongate sandbags 12 filled with sand on the ground surface in courses on top of one another with an inner side of the stacked sandbags being supported by the temporary support structure to form a wall. Thereafter, an outer side of the stacked sandbags is plastered with mortar which is allowed to set so as to stabilize the sandbags and support the wall. The temporary support structure is then removed and the inner side of the sandbags is plastered with mortar which is allowed to set and cure.

Description

A CONSTRUCTION METHOD AND SYSTEM FOR CONSTRUCTING

A WALL OF A BUILDING STRUCTURE

FIELD OF INVENTION

The invention relates to a construction method and system for constructing a wall. It relates also to a construction method and system for constructing a building structure. In this specification, the term "sand" must be interpreted to mean any type of sand, earth or any fluent particulate material.

SUMMARY OF INVENTION

According to a first aspect of the invention there is provided a construction method for constructing a wall, the construction method including: providing sandbags filled with sand; locating a temporary support structure in an upright configuration adjacent a ground surface upon which the wall is to be constructed; stacking the sandbags on the ground surface in courses on top of one another with one side of the stacked sandbags being supported by the temporary support structure; applying a settable material to an opposite side of the stacked sandbags so as to form a layer of settable material; and allowing the settable material layer to set sufficiently to stabilize the sandbags and support the wall in an erect configuration.

More particularly, the settable material applied to said opposite side of the stacked sandbags may be in the form of mortar, which forms a mortar layer. The method may include plastering an outer side of the mortar layer with plaster so as to form a plaster layer on top of the mortar layer. The method may include reinforcing the plaster layer so as to form a reinforced plaster layer.

The method may include removing the temporary support structure after the settable material layer has set. The method may include applying settable material to said one side of the stacked sandbags after removal of the temporary support structure, so as to form an additional layer of settable material. The settable material forming the additional layer of settable material may be in the form of mortar, which forms an additional mortar layer. The method may include plastering an outer side of the additional mortar layer with plaster so as to form an additional plaster layer on top of the additional mortar layer.

The method may include providing sandbags having an elongate tubular configuration. The sandbags may have a length dimension of between 300mm and 1000mm when unfilled and laid flat. The sandbags may have a width dimension of between 150mm and 320mm when unfilled and laid flat. The method may include filling the sandbags such that the filled stacked sandbags have a width dimension of between 100mm and 250mm. The method may include filling the sandbags such that filled stacked sandbags have a length dimension of between 150mm and 850mm. The applicant has found that when the stacked sandbags reach a height of 1 , 5 meters, the stacked sandbags topple if not supported by the temporary support structure.

The invention extends to a wall constructed by the construction method described and defined hereinabove. According to a second aspect of the invention there is provided a construction system for constructing a wall, the construction system including: a number of sandbags which can be filled with sand; a temporary support structure which is locatable in an upright erected configuration adjacent a ground surface upon which the wall is to be constructed, for supporting sandbags which are filled with sand and stacked, in use, adjacent the erected support structure, on the ground surface in courses on top of one another, with the temporary support structure supporting one side of the stacked sandbags; and settable material having adhesive properties sufficient such that when a layer of settable material is applied, in use, to an opposite side of the stacked sandbags and allowed to set, the settable material layer supports the sandbags in an erect configuration so as to render the wall self supporting and thereby permitting removal of the temporary support structure.

Each sandbag may have an elongate tubular configuration. The sandbags may have a length dimension of between 300mm and 1000mm when unfilled and laid flat. The sandbags may have a width dimension of between 150mm and 320mm when unfilled and laid flat.

The invention extends to a wall constructed by the construction system described and defined hereinabove.

According to a third aspect of the invention there is provided a construction method for constructing a building structure, the construction method including: constructing at least one wall in accordance with the construction method of the first aspect of the invention and which surrounds a ground area to be covered by a roof; providing removable roof formwork for forming the roof; locating the removable roof formwork on the temporary support structure, above a top end of the wall and above and spanning across the ground area to be covered by the roof; applying at least one layer of settable material to an upper major side of the formwork and onto the top end of the wall; allowing the settable material to set so as to form the roof; and removing the removable roof formwork, so that the roof is supported by the wall.

The method may include applying a layer of plaster to the upper major side of the roof formwork so as to form a first plaster layer and applying a layer of mortar to the first plaster layer so as to form a mortar layer. The method may include applying a layer of plaster to the mortar layer so as to form a second plaster layer. The mortar may be in the form of low density mortar which includes a low density material having a density relatively lower than a density of any other constituent of the mortar.

The method may include reinforcing at least one of the first plaster layer and the second plaster layer with reinforcing material, so as to form at least one of a first reinforced plaster layer and a second reinforced plaster layer.

The settable material layer of the wall and the settable material layer of the roof may be continuous with one another so that the wall and the roof form a unitary structure.

The invention extends to a roof constructed by the construction method described and defined hereinabove. The invention extends also to a building structure constructed by the construction method described and defined hereinabove. According to a fourth aspect of the invention there is provided a construction system for constructing a building structure, the construction system including: removable roof formwork which is configured and dimensioned to span across a ground area to be covered by a roof and which is locatable, in use, above at least one wall which is constructed with the construction system of the second aspect of the invention and which at least partially surrounds a ground area to be covered by the roof; and settable material which is applied to an upper major side of the roof formwork and onto a top end of the wall, in use, and which is settable so as to form the roof, thereby permitting removal of the formwork such that the roof is supported by the wall.

The upper major side of the roof formwork may have a convex shape such that the roof formed by the roof formwork has a convex shape. More particularly, the upper major side of the roof formwork may be dome shaped, such that the roof formed by the roof formwork has a dome shape.

The settable material may include one or more of plaster and mortar. More specifically, the plaster may be reinforced with reinforcing materials. The mortar may be in the form of low density mortar which contains low density material having a density relatively lower than a density of any other constituent of the mortar.

The invention extends to a roof constructed by the construction system described and defined hereinabove. The invention extends also to a building structure constructed by the construction system described and defined hereinabove.

BRIEF DESCRIPTION OF DRAWINGS Further features of the invention are described hereinafter by way of a non-limiting example of the invention, with reference to and as illustrated in the accompanying schematic drawings. In the drawings:

Figure 1 shows a fragmentary perspective view of a construction system in accordance with the invention and a building structure being constructed with the construction system, shown in schematic partially cut-away view to show hidden detail;

Figure 2a shows a perspective view of a sandbag of the construction system of Figure 1 ; Figure 2b shows the sandbag of Figure 2a, shown after having been compacted, in use;

Figure 3 shows a fragmentary sectional view through a wall and a roof of the building structure of Figure 1 , sectioned along section lines Ill-Ill of Figure 1 ; and

Figure 4 shows a perspective view of the construction system and the building structure of Figure 1 , showing a schematic cut-away view to show hidden details of the building structure.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to the drawings, a construction system, in accordance with the invention, is designated generally by the reference numeral 10.

The construction system 10 includes broadly a number of sandbags 12; a temporary support structure 14; settable material in the form of low density cement mortar 16 and cement plaster 17; lintels 18; removable roof formwork in the form of a number of roof formers 19 and reinforcing mesh 20.

The construction system 10 is configured for constructing low cost building structures such as, for example, a building structure 6 having walls 7 and a roof 8 spanning upper ends of the walls 7. The sandbags 12 are configured to be stacked on top of one another, so as to form the walls 7 of the building structure 6. Each sandbag 12 is formed of a flat sheet of woven synthetic plastic material such as, for example, polypropylene, which is folded double and stitched along adjacent sides 21 , 22 so as to form seams 23, 24, respectively and so as to define a hollow tubular open-topped bag-like structure having an open end 26 and an opposite closed end 28. The Applicant envisages that in another embodiment, the sandbags may be made of tubular material in which case they would not be stitched and will not have a seam. The sandbags have a length dimension of 900mm and a width dimension of 150mm, when unfilled and laid flat. The applicant has found that sandbags having a length dimension of between 300mm and 1000mm and a width dimension of between 150mm and 320mm, when unfilled and laid flat, may also be used. In use, the sandbags 12 are filled with sand such as, for example, earth material collected from the building site upon which it is desired to construct the building structure 6. In use, the sandbags 12 are filled by filling the sandbags 12 with earth material introduced into the sandbags 12 via the open ends 26 of the sandbags 12. More particularly, the sandbags 12 are supported in a vertical position and are filled with earth to within 100 to 150mm of the open top of each sandbag 12 and the earth material is then compacted. An open end region of the sandbag 12 is then twisted and folded over and the sandbag is laid horizontally with the folded over part tucked under the earth-filled portion of the sandbag, as shown in Figure 2b of the drawings, so as to keep the earth material within the sandbag 12. If necessary, the earth material may be stabilized by adding cement to the earth material, if required, although this is generally not necessary.

The temporary support structure 14 is configured for temporarily supporting the sandbags 12 during construction of the walls 7 and for temporarily supporting the roof formers 19 during formation of the roof, as will be explained in more detail hereinbelow.

The temporary support structure 14 includes a number of steel frame members 32; a number of timber lengths 34 and a number of lengths of twine 36. The steel frame members 32 are of right angled steel sections or so-called "angle bar" of 40mm by 40mm by 3mm thickness. These steel frame members 32 are all precut, predrilled and premarked so as to facilitate easy and fast assembly of the temporary support structure 14, as will be explained in more detail hereinbelow. The low density cement mortar 16 comprises, by volume, one part cement; three parts sand; twelve parts expanded polystyrene beads (or recycled polystyrene granules); 10ml to 50ml liquid surfactant and sufficient water per hand agitated volume of mixture to ensure a trowellable consistency. The cement plaster 17 is in the form of standard cement plaster to which a water proofing agent has been added.

The roof formers 19 include roof formers 19.1 and 19.2, which are each configured for forming the roof 8 of the building structure 6, as will be explained in more detail hereinbelow. The roof formers 19.1 , 19.2 are of timber lengths and sheet material and include a curved top panel 39 and a pair of spaced side panels 40 disposed at opposite long sides of the curved top panel 39, as illustrated in Figures 1 and 3 of the drawings. The top panel 39 of each roof former 19.1 , 19.2 has an upper major side having a convex, dome shaped configuration. The reinforcing mesh 20 is in the form of fiber glass or similar suitable reinforcing material having strands orientated at right angles to one another and being spaced approximately 10mm apart from one another.

A construction method, in accordance with the invention, will be described hereinbelow, with reference to the drawings and with reference to construction of the building structure 6 illustrated in the drawings. As a first-step, the ground upon which it is desired to construct the building structure 6 must be prepared. More specifically, a standard concrete foundation is laid. Alternatively, a foundation of wide double-tube earth filled sandbags, or alternatively, a rubble trench foundation may be prepared. The applicant has also found that in certain circumstances a foundation, as described above may be dispensed with, and the earth may simply be compacted to form a suitable foundation. In use, the temporary support structure 14 is erected upon the foundation by connecting the marked steel frame members 32 to one another by bolting them together via pre-marked and predrilled holes. The correct vertical and horizontal orientation of the connected steel frame members 32 is ensured by leveling and squaring a base of the frame formed of the steel frame members 32 and by securing steel frame members in a diagonal orientation so as to form diagonal brace members 37, as illustrated in Figure 1 of the drawings. The Applicant envisages that diagonally-extending tensioning wires can also be used as brace members instead of the steel frame members, for ensuring that the steel frame members of the temporary support structure are held square and vertical.

Furthermore, the Applicant envisages that brackets (not shown) can be located at corners of the temporary support structure to ensure that the steel frame members are held in a mutually orthogonal configuration at the corners of the support structure. Timber lengths 34 are then arranged so as to extend vertically between the steel frame members 32 with the timber lengths 34 being spaced approximately 500mm apart from one another. Selected timber lengths 34 are then cut and arranged so as to define door openings 38.1 and window opening 38.2, as illustrated in Figure 1 of the drawings. More specifically, the timber lengths 34 are secured to the steel frame members 32 by tying the timber lengths 34 to the steel frame members 32 by means of the twine 36.

In use, the temporary support structure 14 is configured for guiding the position of the sandbags 12 and for supporting the sandbags 12, as illustrated in Figure 1 of the drawings. In use, a first course of filled sandbags 12 are laid adjacent the erected temporary support structure 14 so as to cover a ground surface upon which a wall of the building structure 6 is to be build. More specifically, the sandbags 12 are placed in an end to end arrangement, as illustrated in Figure 1 of the drawings, with the open end region of each sandbag 12 being folded and twisted closed and folded underneath the earth-filled portion of the sandbag, as illustrated in Figure 2b of the drawings. The sandbags 12 are then compacted from above so that the sandbags 12 assume an oval shape, as illustrated in Figure 2b of the drawings, such that a height dimension of each sandbag 12 is slightly less than a width dimension thereof. More particularly, when filled, stacked and compacted, each sandbag 12 has a length of approximately 750mm, a width of approximately 1 10mm and a height of approximately 70mm.

In use, further sandbags 12 are then stacked in courses on top of one another, as illustrated in Figure 1 of the drawings, so as to form wall structures. More particularly, the sandbags 12 are arranged in rows, with the folded ends of one sandbag being laid adjacent to an end of an already placed sandbag, such that the folded ends prevent the earth material from escaping the sandbag 12 and maintains the rigidity of the sandbags 12. As shown in Figure 1 of the drawings, each sandbag 12 overlaps two sandbags 12 beneath it, in the fashion of a "running bond", as is used in masonry and brick laying. The sandbags are also arranged so as to overlap one another in the corners of adjacent walls, as illustrated in Figure 1 of the drawings. In use, after each sandbag 12 is located upon an adjacent sandbag and adjacent the temporary support structure 14, twine 36 is used to tie the sandbag 12 onto adjacent steel frame members 32 and/or onto adjacent timber lengths 34, such that the temporary support structure 14 secures, locates, and supports one side of the sandbags 12, as shown in Figure 1 of the drawings. The applicant has found that it is particularly advantageous to arrange the sandbags 12 such that the seams 23 of the sandbags 12 extend outwardly, as shown in Figure 1 of the drawings, the reason for this will be explained in more detail hereinbelow. The sandbags 12 are thus stacked, in use, so as to define the walls 7 of the building structure 6 and to define the door openings 38.1 and the window openings 38.2. More specifically, the lintels 18 will be placed so as to span and define tops of the door openings 38.1 and the window openings 38.2 and so as to support the sandbags 12 stacked upon the lintels 16, as illustrated in Figure 4 of the drawings.

In use, after all the sandbags 12 have been stacked and located as described hereinabove, the low density cement mortar 16 is applied to an opposite side of the stacked sandbags and trawled flat, as illustrated in Figures 1 and 3 of the drawings, so as to encapsulate the sandbags 12 and particularly the protruding seams 23 and so as to form a mortar layer 41 of not less than 40mm in thickness when measured beyond an outer curve of the sandbags 12 embedded in the mortar layer. Once the mortar layer 41 has set, the mortar layer 41 embeds the sandbags 12 therein and stabilizes the sandbags 12 so as to support the wall in an erect configuration. It will be appreciated that the mortar 16 has adhesive property sufficient such that when the mortar layer 41 is allowed to set, the mortar layer 41 supports the sandbag in an erect configuration, so as to render the wall self supporting. The applicant has found that the mortar layer 41 adheres to the sandbags, clings to the sandbags weave and attaches to the projecting seams 23 of the sandbags 12, thereby stabilizing the sandbags 12. Furthermore, the mortar layer 41 fills the curved recesses defined between the stacked sandbags 12, as illustrated in Figure 3 of the drawings.

In use, the roof formers 19.1 , 19.2 are placed on top of the temporary support structure 14 so as to be supported above upper ends of the walls formed of the stacked sandbags 12. In use, a thin layer of cement plaster 17 is then applied to the upper surface of the roof formers 19.1 , 19.2 and reinforcing mesh 20 is laid out and imbedded in the plaster 17 and covered with more plaster 17 to form a mesh reinforced plaster layer 42 of approximately 10mm. In use, the mesh reinforced plaster layer 42 is formed so as to extend beyond the roof formers 19.1 , 19.2 and onto and over a top row of sandbags 12 and over the thick insulating low density cement mortar layer 41 of the wall, in the manner illustrated in Figure 3 of the drawings. In use, a thick layer of low density cement mortar 16 is then applied onto the mesh reinforced plaster layer 42 applied on top of the roof formers 19.1 , 19.2. More specifically, the cement mortar 16 is applied so as to form a mortar layer 41 having a depth of approximately 100mm, with the mortar layer 41 extending beyond the roof formers 19.1 , 19.2 and onto the sandbags 12, so as to be continuous therewith and so as to form a thick insulating mortar layer 41 which is continuous with the mortar layer 41 of the wall, as best shown illustrated in Figure 3 of the drawings. In use, the dried cement mortar layer 41 of the walls 7 and roof 8 of the building structure 6 are then lightly plastered with plaster 17 and draped with mesh 20 and plastered with a further thin plaster layer so as to form a mesh reinforced plaster layer 42 of approximately 10mm in depth. With reference to Figure 3 of the drawings, a water catchment element 43 is then formed along an outer side of the roof 8, as illustrated in Figure 3 of the drawings. As shown in Figure 4 of the drawings, a plane P1 which is planar with an edge region of the roof 8 and a plane P2 which is planar with a wall region of the building structure 6, together define an angle a between them of approximately 1 10 °, as best illustrated in Figure 3 of the drawings.

The applicant envisages that the temporary support structure 14 can be removed after the mortar layer 41 has set. Thereafter the inner side of the walls 7 of the building structure 6 can be covered with additional cement mortar 16 and allowed to set. After setting of the additional cement mortar 16 so as to form an additional inner low density cement mortar layer 44, as illustrated in Figure 3 of the drawings, a layer of additional plaster 17 is applied to an outer side of the inner low density cement mortar layer 44 so as to form an additional flat inner plaster wall surface layer 45, which is suitable for painting or finishing in a desired manner.

The applicant has found that in an alternative method (not illustrated in the drawings), as an alternative to covering the inner side of the stacked sandbags with cement mortar 16, the inner side of the stacked sandbags are plastered with a layer of plaster only. More specifically, in this alternative method, the low density cement mortar 16 and the mortar layers 41 and 44 described hereinabove, are omitted entirely. As such, only a plaster layer is applied directly to the opposite sides of the stacked sandbags. It will be understood that the plaster has adhesive properties sufficient such that the plaster layer supports and stabilizes the sandbags when the plaster layer sets.

The applicant envisages that the building structure 6 is structurally sound due to one or more of the following: the tensile strength of the walls 7 due to the long and overlapping configuration of the sandbags 12; the dynamic balance between the opposing compressing force creating by the mass of the earth material inside the side bag 12 and the tensile strength of the sandbag 12; the structural continuity of the roof 8 and walls 7 which form a monolithic unitary structure; the roof 8 and the walls 7 creating stiffness in two planes, P1 and P2 which planes are orientated at an angle of approximately 1 10 ° relative to one another and which provides for the outward pressure of the arch roof to be resisted by the walls; the curved self supporting roof structure 8 which creates a flexible diaphragm connecting tops of opposite and adjacent walls and maintaining over all rectangular form of the building structure 6. The applicant has found that a multilayered "sandwich construction" of settable material which forms the roof 8, as illustrated in Figure 3 of the drawings, is particularly advantageous. As shown in Figure 3 of the drawings, the "sandwich construction" comprises the relatively "thick" low density mortar layer 41 "sandwiched" in between the relatively "thin" mesh reinforced plaster layers 42 which have relatively high compression and tensile strengths. More specifically, the applicant has found that the "sandwich construction" provides a relatively low density roof having a high degree of stiffness. The applicant has found that this stiffness when combined with the dome / arch shape of the roof allows the roof to be self supporting.

The applicant believes that the construction system 10 is advantageous as it allows the formation of structurally sound building structures having walls with relatively narrow widths, when compared to widths of other known sandbag build walls. This feature is particularly due to the comparatively narrow width of the sandbags 12 when compared to widths of known sandbags used for constructing walls. As such, the applicant has found that the construction of structurally sound building structures using the sandbags 12 is made possible by providing temporary support to the sandbags 12, which are inherently unstable when stacked upon one another. The applicant has found that when the stacked sandbags 12 reach a height of 1 , 5 meters, the stacked sandbags topple if not supported by the temporary support structure 14. The applicant has found that construction is made possible by providing the temporary support structure 14 which stabilizes the stacked sandbags 12 during construction. After construction and removal of the temporary support structure 14, the applicant has found that the mortar layer 41 supports the sandbags 12, such that the wall is rendered self-supporting.

The applicant envisages that the construction system 10 is particularly advantageous for building low cost building structures to serve as in-situ upgrades of informal dwellings. More specifically, the building structure 6 may be erected around and over existing dwelling, such as, for example, "a shack" which is then removed from within the newly erected and completed building structure 6. As such, the applicant envisages that this allows relative uninterrupted occupation of the area defined by the shack, while the building structure 6 is being constructed. As such the applicant has found that the construction system 10 is advantageous particularly in regions such as for example informal settlements where availability of land is scarce and as such the building structure 6 must essentially occupy the same land upon which the shack is built.

The applicant has also found that the construction system 10 is particularly beneficial as it offers one or more of the following benefits, namely, cost reduction benefits compared to conventional construction methods; reduction of building materials used; cost reduction resulting from reduced transport costs; increased durability due to absence of steel or timber which is susceptible to rot and corrosion; enhanced fire resistance properties; and enhanced thermal and acoustic insulation efficiency. Furthermore, the applicant has also found that the construction system 10 is particularly beneficial as it can be used by unskilled workers and requires a minimal of site and foundation preparation.

The applicant has also found that the narrow and long dimensions of the sandbag 12 and the method of filling and compaction of the sandbags is advantageous because the outward pressure of the earth material is resisted by the tensile strength of the sandbag, resulting in a relatively rigid tube-shaped sandbag which helps maintain both cross section and straight line shape of the sandbag when being used to construct the wall.

Claims

A construction method for constructing a wall, the construction method including: providing sandbags filled with sand; locating a temporary support structure in an upright configuration adjacent a ground surface upon which the wall is to be constructed; stacking the sandbags on the ground surface in courses on top of one another with one side of the stacked sandbags being supported by the temporary support structure; applying a settable material to an opposite side of the stacked sandbags so as to form a layer of settable material; and allowing the settable material layer to set sufficiently to stabilize the sandbags and support the wall in an erect configuration.

The construction method as claimed in claim 1 , wherein the settable material applied to said opposite side of the stacked sandbags is in the form of mortar, which forms a mortar layer.

The construction method as claimed in claim 2, which includes plastering an outer side of the mortar layer with plaster so as to form a plaster layer on top of the mortar layer.

The construction method as claimed in claim 3, which includes reinforcing the plaster layer so as to form a reinforced plaster layer.

The construction method as claimed in claim 3, which includes removing the temporary support structure after the settable material layer has set.

6. The construction method as claimed in claim 5, which method includes applying settable material to said one side of the stacked sandbags after removal of the temporary support structure, so as to form an additional layer of settable material.

7. The construction method as claimed in claim 6, wherein the settable material forming the additional layer of settable material is in the form of mortar, which forms an additional mortar layer.

8. The construction method as claimed in claim 7, which includes plastering an outer side of the additional mortar layer with plaster so as to form an additional plaster layer on top of the additional mortar layer.

9. The construction method as claimed in any one of claims 1 to 8, which includes providing sandbags having an elongate tubular configuration.

10. The construction method as claimed in claim 9, wherein the sandbags have a length dimension of between 300mm and 1000mm when unfilled and laid flat.

1 1 . The construction method as claimed in claim 10, wherein the sandbags have a width dimension of between 150mm and 320mm when unfilled and laid flat.

12. The construction method as claimed in claim 1 1 , which includes filling the sandbags such that the filled stacked sandbags have a width dimension of between 100mm and 250mm.

13. The construction method as claimed in claim 12, which method includes filling the sandbags such that filled sandbags have a length dimension of between 150mm and 850mm.

14. A wall constructed by the construction method in accordance with any one of claims 1 to 13.

15. A construction system for constructing a wall, the construction system including: a number of sandbags which can be filled with sand; a temporary support structure which is locatable in an upright erected configuration adjacent a ground surface upon which the wall is to be constructed, for supporting sandbags which are filled with sand and stacked, in use, adjacent the temporary support structure in its erected configuration, on the ground surface in courses on top of one another, with the temporary support structure supporting one side of the stacked sandbags; and settable material having adhesive properties sufficient such that when a layer of settable material is applied, in use, to an opposite side of the stacked sandbags and allowed to set, the settable material layer supports the sandbags in an erect configuration so as to render the wall self supporting and thereby permitting removal of the temporary support structure.

16. The construction system as claimed in claim 15, wherein each sandbag has an elongate tubular configuration.

17. The construction system as claimed in claim 16, wherein the sandbags have a length dimension of between 300mm and 1000mm when unfilled and laid flat.

18. The construction system as claimed in claim 17, wherein the sandbags have a width dimension of between 150mm and 320mm when unfilled and laid flat.

19. A wall constructed by the construction system in accordance with any one of claims 15 to 18.

20. A construction method for constructing a building structure, the construction method including: constructing at least one wall in accordance with the construction method of the first aspect of the invention and which surrounds a ground area to be covered by a roof; providing removable roof formwork for forming the roof; locating the removable roof formwork on the temporary support structure, above a top end of the wall and above and spanning across the ground area to be covered by the roof; applying at least one layer of settable material to an upper major side of the formwork and onto the top end of the wall; allowing the settable material to set so as to form the roof; and removing the removable roof formwork, so that the roof is supported by the wall.

21 . The construction method as claimed in claim 20, which includes applying a layer of plaster to the upper major side of the roof formwork so as to form a first plaster layer and applying a layer of mortar to the first plaster layer so as to form a mortar layer.

22. The construction method as claimed in claim 21 , which includes applying a layer of plaster to the mortar layer so as to form a second plaster layer.

23. The construction method as claimed in claim 22, wherein the mortar of the mortar layer, is in the form of low density mortar which includes a low density material having a density relatively lower than a density of any other constituent of the mortar.

24. The construction method as claimed in claim 23, which includes reinforcing at least one of the first plaster layer and the second plaster layer with reinforcing material, so as to form at least one of a first reinforced plaster layer and a second reinforced plaster layer.

25. The construction method as claimed in any one of claims 20 to 24, wherein the settable material layer of the wall and the settable material layer of the roof are continuous with one another so that the wall and the roof form a unitary structure.

26. A building structure constructed in accordance with the construction method as claimed in any one of claims 20 to 25.

27. A construction system for constructing a building structure, the construction system including: removable roof formwork which is configured and dimensioned to span across a ground area to be covered by a roof and which is locatable, in use, above at least one wall which is constructed with the construction system as claimed in any one of claims 15 to 18 and which at least partially surrounds a ground area to be covered by the roof; and settable material which is applied to an upper major side of the roof formwork and onto a top end of the wall, in use, and which is settable so as to form the roof, thereby permitting removal of the formwork such that the roof is supported by the wall.

28. The construction system as claimed in claim 27, wherein the upper major side of the roof formwork has a convex shape such that the roof formed by the roof formwork has a convex shape.

29. The construction system as claimed in claim 28, wherein the upper major side of the roof formwork is dome-shaped, such that the roof formed by the roof formwork has a dome shape.

30. The construction system as claimed in claim 28 or claim 29, wherein the settable material includes one of plaster and mortar.

31 . The construction system as claimed in claim 30, wherein the plaster is reinforced with reinforcing materials.

32. The construction system as claimed in claim 31 , wherein the mortar is in the form of low density mortar which contains low density material having a density relatively lower than a density of any other constituent of the mortar.

33. A roof constructed in accordance with the construction system as claimed in any one of claims 27 to 32.

4. A building structure constructed in accordance with the construction system claimed in any one of claims 27 to 32.