BACKGROUND TO THE INVENTION Traditional methods using bricks and mortar require a degree of skill, and structures erected by bricklayers tend to be too expensive for low cost or sub- economic housing. There is as a consequence a need for a building block which can be used by labourers who have had a minimum amount of training in building procedures.

BRIEF DESCRIPTION OF THE INVENTION According to one aspect of the present invention there is provided a method of building a wall which comprises building a lower course of alternate first and second blocks, the first blocks being of greater height than the second blocks and the blocks having vertically extending ribs and grooves, interlocking the blocks in the lower course against relative horizontal movement by inserting the ribs into the grooves, and building an upper course of the wall on the lower course by inserting blocks from above into the gaps bounded at their lower ends by second blocks and along opposed vertical sides thereof by first blocks, the blocks in the upper course

extending to above the tops of the first blocks in the lower course whereby the sides of these blocks and the top faces of the first blocks define further gaps for receiving still further blocks from above.

According to a further aspect of the present invention there is provided a building block having major front and rear faces and end faces at right angles to the major faces, the block having a vertically extending recess in one of the vertically extending end faces thereof and a vertically extending rib on another of the faces thereof, the rib and recess being of compatible shape so that the rib of one block can be slid into the recess of another block of the same configuration by relative movement between the blocks in the vertical direction.

According to another aspect of the present invention there is provided a method of building a wall which comprises casting blocks which have major front and rear faces and end faces at right angles to the major faces, the blocks each having a vertically extending recess in one of the vertically extending end faces thereof and a vertically extending rib on another of the faces thereof, the ribs and recesses being of compatible shape so that the rib of one block can be slid into the groove of another block of the same configuration, and interlocking the blocks by displacing them vertically with respect to one another so that the rib of each block enters the groove of a further block.

According to a still further aspect of the present invention there is

provided a pair of interlockable building blocks, each block having a major front face, a major rear face and end faces at right angles to the major faces, a first of the blocks having two vertically extending ribs and a second of the blocks having two vertically extending recesses, the ribs and recesses being of compatible shape so that the rib of a first block can be slid into the recess of a second block by relative movement between the blocks in the vertical direction.

According to yet another aspect of the present invention there is provided a pair of interlockable building blocks, one of the blocks including a vertically extending rib and the other block including a vertically extending recess of a shape which is compatible with that of the rib so that the rib can enter the recess, the recess being bounded by faces two of which have grooves therein, the grooves facing one another across the recess, and the ribs having grooves in opposed bounding faces thereof, the grooves of the blocks being in register when the rib is in the recess thereby to define two vertically extending channels.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which :- Figure 1 is a top plan view of a building block; Figure 2 is a side elevation of the block;

Figures 3 and 4 are end elevations of the block, the elevations being taken in opposite directions; Figures 5a and 5b are top plan views of further blocks; Figure 6 is a top plan view of a corner block; Figure 7 is a top plan view of a block which enables an outer wall to be connected to an inner wall; Figure 8 is a top plan view of the block of Figure 5a and showing the attachment of a stile to the block; Figure 9 is an elevation of a partially erected wall constructed using the block of Figures 1 to 4 and the block of Figure 6; Figure 10 illustrates a full height block and a half height block which are longer than the blocks of the preceding Figures; Figure 11 shows a window construction; Figure 12 shows the fixing of a wall plate; Figure 13 shows a cap for a screen wall; and Figure 14 is a plan view of parts of two further blocks.

DETAILED DESCRIPTION OF THE DRAWINGS Referring firstly to Figures 1 to 5, the cast concrete block illustrated is designated 10 and comprises parallel front and rear walls 12 and 14. The walls 12 and 14 are connected by two webs 16 and 18 which extend in the front to rear direction of the block. The web 16 forms one end face of the block. The walls 12 and 14 and webs 16 and 18 define a vertically extending cavity 20. The cavities 20,

when the blocks are stacked in columns, extend the full height of the wall as vertical passageways and can receive service pipes or cables.

A vertically extending rib 22 is integral with the web 16. The rib 22 thus protrudes from one of the vertically extending end faces of the block. The rib 22 is substantially square in horizontal cross section (see Figure 1). A vertically extending vee-shaped groove is provided in each of the front and rear faces of the rib 22. The front groove is designated 24 and the rear groove is designated 26. The grooves 24,26 are each bounded by two flanks that meet at an apex.

A vertically extending recess 28 is provided at the other end of the block 10. The recess 28 is bounded by the web 18 and parts of the walls 12 and 14 which protrude beyond the web 18. The inner faces of the protruding parts of the walls 12 and 14 are moulded with vertically extending protrusions, the front protrusion being designated 30 and the rear protrusion being designated 32. Each protrusion is bounded by two flanks which meet at an apex. It will be understood that the protrusions can be on the rib 22 and the grooves in the faces of the walls 12,14.

The chain dotted lines in Figure 1 illustrate the positions of those blocks which, in a wall, are adjacent the block 10.

Figure 5a illustrates a block 150 which has a recess 28.1 at one end

and a recess 28.2 at the other end. In Figure 5b the block 152 has a rib 22.1 at one end and a rib 22.2 at the other end.

The block 110 of Figure 6 differs from the block 10 of Figures 1 to 4 in that the rib 122 protrudes from the front wall 112 and not from the web 116. The rib 122 could, of course, protrude from the rear wall 114 instead of from the front wall 112.

The remaining parts of the block 100 carry reference numerals corresponding to those used in Figure 1 increased in magnitude by 100.

The block 210 of Figure 7 has, in addition to the rib 222, a second rib 234. Figure 7 additionally illustrates the way in which the recess 228 can be closed by a vertically extending plate 236 which includes grooves 224,226 compatible with the protrusions 230,232.

The blocks are cast as full height blocks and half height blocks.

Alternatively, all the blocks can initially be of the same height and a number of blocks 10 can be cut in half along a horizontal line midway between the top and bottom faces. The half blocks are designated 10.1 in Figure 9 which shows how a wall is erected. The full height blocks 10 are designated 10.2 and the wall also includes full height blocks 110 as shown in Figure 6. A full height block 110 is placed at the left hand end of a foundation F. A first half block 10.1 is placed next to

it by sliding the rib 22 down the recess 28. The protrusions 30 and 32 enter and slide down the grooves 24 and 26 thus interlocking the blocks against relative horizontal movement. Half blocks 10.1 and full blocks 10.2 are placed alternately on the foundation F thereby to produce a lower course of blocks. Another full height block 110 is used at the other end of the foundation.

To form an upper course, full height blocks 10.2 are slid vertically from above, as diagrammatically shown in Figure 9 by means of arrows A, into the gaps defined by the side faces of the upper parts of the full height blocks 10.2 in the lower course until they rest on the half blocks 10.1. The upper parts of the full height blocks in the second course are above the full height blocks 10.2 of the lower course, thereby defining further gaps for receiving still further blocks which rest on the tops of the blocks 10.2 of the lower course. This procedure continues using full height blocks 10.2 and 110 until the wall reaches its desired height. Half blocks 10.1 (not shown in Figure 9) are then inserted from above into the gaps between the top course of full height blocks 10.2,110. This results in a horizontal top surface on which a wooden wall plate is placed as will be described in more detail hereinafter.

Blocks 210 as shown in Figure 7 are used in any vertical column where an inside wall of the building is to join the outside wall shown in Figure 9.

The blocks 150 and 152 shown in Figures 5a and 5b are used alternately to build a wall. Thus, except at the ends of the wall, each block 150 is

between blocks 152 and each block 152 is between blocks 150. Any recesses 28.1 which are exposed when the wall is finished can be closed off as described with reference to Figure 7 by a plate 236. The blocks 150,152 can have recesses and ribs positioned so that they can act as corner blocks and as blocks which permit internal walls to be joined to outside walls.

At the right hand end of Figure 8 there is illustrated a method of building the stile 334 of a door frame into the wall. The edges of the stile 334 are chamferred at 336 so that they conform in shape to one flank of each protrusion 330 and 332. A metal plate 338 is secured by screws 340, or in any other manner, to the stile 334. The ends of the plate 338 are bent over so that, with the chamfers of the stile 334, they define grooves each of which is of the same shape as the protrusions 330 and 332. The stiles can thus be slid vertically from above into the vertically aligned recesses 328.1 or 328.2 of the vertical stacks of blocks which border the door frame.

If blocks which are wider than those illustrated are to be used a third web can be introduced. This is shown in Figure 10 which illustrates a half block 410.1 and a full height block 410.2 which are interengaged. The additional web is shown at 434. The blocks of Figure 10 also illustrate that it is possible to recess the top face of the block to leave two flat lands 436 which the block above abuts. The recess in the top face of the block is designated 438. Such recesses are provided in the top faces of all the blocks described.

Where a window is to be fitted (see Figure 11) a frame 534 is placed on top of the full height blocks, designated 10.2, and half height blocks, designated 10.1, which lie beneath the window opening 536. The frame 534 includes a cill 538, two stiles 540 and a top member 542. The cill 538 lies in the recesses 438 of the course of blocks below the window opening. Further blocks are then positioned adjacent the frame 534, the stiles 540 entering the recesses of these blocks. A lintel 544 is then placed over the window opening with its ends in the recesses 438 of the blocks in the columns bounding the window opening 536. The blocks in the course of blocks above the lintel 544 are positioned in an inverted orientation. The lintel 544 is thus between the adjacent courses in the horizontal extending space which is created by the juxtaposed recesses 238 of the inverted blocks and the blocks beneath the inverted blocks. The lintel can be of wood but is preferably of cast concrete.

When the blocks are interlocked, as shown in Figure 1, vertically extending passages 34 (see Figure 1) remain between the webs 18 and the ribs 22.

These passages can receive rods 36 (see Figure 12) which extend from, for example, the horizontal joint line 38 between the third and fourth courses down (counting from the top course) to above the wall plate designated 40. The wall plate 40 has a hole drilled therein to receive the rod 36. The rod 36 has a plate 42 at the lower end thereof which is larger in dimensions than the passage 34 and is in the recess 438 of that block which is below the plate 42. At the upper end the rod 36 there is a nut 44. The nut 44 is threaded onto the part of the upper end of the rod 36

which is above the waii plate 40. A series of rods 36 are provided along the wall.

When the nuts 44 are tightened, the plates 42 are pulled against the lower faces of the blocks above them and the wall plate 40 is pressed down against the top faces of the top course of blocks. The passages 34 can be filled with mortar.

If the blocks are to be used in a multi-storey construction, reinforcing rods 46 (Figure 9) have their lower ends embedded in the foundation F and extend upwardly through some of the passageways constituted by the vertically aligned cavities 20,120 etc. The rods protrude above the top course of blocks of the lower storey. The cavities 20,120 of the top course of blocks which do not have rods 46 in them are blocked off, for example, about 20cm down from the top.

When the floor of the first storey is cast on shuttering (not shown) constructed for this purpose, the vertical passageways containing the rods 46 are filled over their full height with concrete to form supporting columns. The passageways which are blocked off near their tops only have concrete in the upper parts thereof. The upper ends of the rods 46 are tied to reinforcing (not shown) which is fabricated on the shuttering and which, when the floor is cast, is embedded in it.

Where the wall is a screen wall and not part of the wall of a building, an elongate reinforced cast concrete member 50 (Figure 13) can be used to cap the wall. The member 50 fits into the recesses 438 of the top course of blocks and is

secured to the blocks by a mortar layer between it and the blocks.

In Figure 14 two blocks 610,612 are shown. The grooves 24,26 and protrusions 30,32 of the block of Figure 1 are replaced by vertically extending semi- circular grooves 614,616. The grooves 614,616 together define vertically extending circular cross-section channels into which dowel pins 618 are inserted to lock adjacent blocks 610,612 against relative movement.