According to the invention there is provided a self-locating building block which has a longitudinal tongue at the top and a shoulder on each opposite side of the longitudinal tongue; a longitudinal groove at the bottom, the longitudinal groove being such that the longitudinal tongue of another such block is receivable in the longitudinal groove when the blocks are laid in superimposed courses; and at least one cavity extending through the block from to bottom, the cavity being at least as wide as the longitudinal tongue so as to give the longitudinal tongue a castellated form in side elevation.

The block may further have a vertical tongue at one end thereof, said vertical tongue extending from top to bottom of the block, and a vertical groove at the other end thereof, the vertical groove being such that the vertical tongue of another such block is receivable in the vertical groove when the blocks are laid end-to-end.

The cavity (or cavities, if there are more than one) may take up at least half the end-to-end

distance of the longitudinal tongue.

The combined width of the shoulders may be at least half the width of the block.

A block according to the invention for use at a corner or T-junction in a wall may have a further vertical groove in a side face thereof, said further vertical groove being such that the vertical tongue of another such block is receivable in said further vertical groove when the blocks are laid in the same course at right angles to one another.

Furthermore, a block according to the invention for use at a corner or T-junction in a wall may have a transversely extending groove at the bottom thereof, the configuration of the transversely extending groove being such that the longitudinal tongue of another block as aforesaid is receivable in the transversely extending groove when the blocks are laid in superimposed courses at right angles to one another.

The invention will now be described in more detail, by way of example, with reference to the accompanying drawings.

In the drawings: Figure 1 is a pictorial view of one form of building block in accordance with the invention,-

Figure 2 is a side elevation of another form of building block in accordance with the invention, for use at a corner or T-junction in a wall;

Figure 3 is a plan view of the building block of Figure 2;

Figure 4 is an end elevation of the building block of Figure 2;

Figure 5 is a pictorial view of another form of building block in accordance with the invention, for use at a corner or T-junction in a wall;

Figures 6 to 9 are plan views of various forms of closing block for use with the blocks of Figures 1 to

5;

Figure 10 is a pictorial view of another form of building block in accordance with the invention; and Figure 11 is a plan view of yet another form of building block in accordance with the invention.

Referring first to Figure 1, reference numeral 10 generally indicates a building block which may conveniently be moulded from a sand-cement mixture. The block has a longitudinal tongue 12 at the top, a shoulder 14 on each opposite side of the tongue, and a longitudinal groove 16 at the bottom. The block 10 further has two cavities 18 extending through the block from top to bottom, i.e. from the groove 16 to the tongue 12. The cavities 18 are as wide as the tongue 12. The effect of this is that the cavities 18 break the tongue 12 up into three tongue portions 12.1, 12.2, and 12.3 respectively, giving the tongue a castellated form in side elevation.

The longitudinal groove 16 is slightly wider than the tongue 12 so that, when a plurality of the building blocks 10 are laid in superimposed courses, the tongues 12 of the building blocks in one course can enter with a little clearance into the groove 16 of the blocks in the successive course.

The two shoulders 14 are of equal width, and their combined width is about 50% of the overall width of the building block. In the example illustrated, the block has an overall width of 140mm, the tongue 12 has a width of 70mm, and the shoulders 14 each have a width

of 35mm. The longitudinal groove 16 has a width that is a few millimetres greater than that of the tongue 12, thus giving some clearance for entry of the tongue 12 and for accommodating slurry, cement paste, or mortar used for bonding the building blocks 10 together when they are laid in superimposed courses to form a wall .

The height of the tongue 12 is about 15mm, whereas the depth of the longitudinal groove 16 is a few millimetres greater, again giving some clearance for accommodating slurry, cement paste, or mortar used for bonding the building blocks 10 together.

In one end face of the building block 10 there is a vertical groove 20, and at the other end the building block has a vertical tongue 22. The vertical tongue 22 is slightly narrower than the vertical groove 20 so that, when a number of the building blocks are laid end-to-end, the tongue 22 of one block can enter with a little clearance into the groove 20 of the adjacent block.

The vertical groove 20 has a depth of 21mm, whereas the vertical tongue 22 protrudes by about 25mm from the corresponding end face of the block.

The extent, in the longitudinal direction of the block, of each of the cavities 18 is 112mm, whereas the end-to-end distance of the tongue 12 (from the bottom of the vertical groove 20 to the end of the vertical tongue 22) is 404mm. Accordingly, the cavities 18 take up approximately 55% of the end-to-end distance of the longitudinal tongue 12.

Referring now to Figures 2 to 4, there is shown a block 10.1 which is similar to the block 10,

the same reference numerals being used to designate the same parts. The block 10.1 differs from the block 10 in that, in one side face thereof, it has a further vertical groove 24, in which the vertical tongue 22 of a block 10 is receivable when the blocks 10.1 and 10 are laid at right angles to one another to form a corner or a T-junction in a wall.

Referring now to Figure 5, reference numeral 10.2 generally indicates a block which, to a lesser extent than the building block 10.1, is similar to the block 10, the same reference numerals being used to indicate the same parts. The building block 10.2 differs from the block 10 in that it has a single cavity 18, in that, in one side face thereof, it has, like the block 10.1, a further vertical groove 24, and in that, on the opposite side, it has a lateral extension 26 with a tongue 28 at the top thereof, the tongue 28 extending at right angles to the tongue 12. The extension 26 has shoulders 30 on opposite sides of the tongue 28, the shoulders 30 being coplanar with the shoulders 14. At the end of the extension 26 there is a vertical tongue 32 whose dimensions are essentially the same as those of the vertical tongue 22. On the underside of the block 10.2 there is a groove (not visible) which extends at right angles to the groove 16 and is able to receive therein the tongue 28 or the tongue 12 of a block 10, 10.1, or 10.2.

Referring now to Figures 6 to 9, reference numerals 10.3, 10.4, 10.5, and 10.6 indicate closing blocks for use in closing up spaces at the end of a wall or where a door or window frame is set into the wall and where the blocks of superimposed courses are staggered with respect to one another, hereas the block 10 has a length of 400mm and a height of 195mm, the blocks 10.3, 10.4, 10.5, and 10.6, whilst having

the same height as the block 10, have lengths of 75mm, 100mm, 125mm and 200mm respectively. Whereas the blocks 10.4, 10,5 and 10.6, which are in accordance with the invention, each have a single cavity 18 therein, the block 10.3, which is not in accordance with the invention, has no cavity therein.

Referring now to Figure 10, reference numeral 10.7 generally indicates a building block which is similar to the building block 10 of Figure 1, the same reference numerals being used to indicate the same or similar parts. The building block 10.7 differs from the building block 10 in that it has a transversely extending groove 40 at the bottom. The distance Dl of the groove 40 from the near end of the block is equal to the width of each of the shoulders 14, whereas the width of the groove 40 is slightly wider than the width of the tongue 12 (constituted by the portions 12.l to 12.3). Thus, when the blocks 10.7 are laid in superimposed courses at a corner or T-junction in a wall, the tongue 12 of the lower block will enter into the groove 40 of the upper block. The exposed vertical groove 20 at the corner or T-junction can later be filled with plaster or other filler material.

The block 10.7 further differs from the block 10 in that, in each of its sides faces, it has a series of vertical score lines 42.1, 42.2, and 42.3. The distance D2 of the first score line and 42.1 from the near end of the block for a block which has a nominal length of 400mm, is 100mm. The distance D3 between the score lines 42.1 and 42.2 is also 100mm, and the distance D4 between the score lines 42.2 and 42.3 is 140mm. This leaves a distance of 60mm between the score line 42.3 and the other end of the block.

The score lines 42.1 to 42.3 are conveniently

formed by scoring when the block is removed from the mould box in which it is moulded.

The score lines 42.1 to 42.3 serve as an aid for the builder in breaking away part of the block when the builder wants to use a shorter block.

Referring now to Figure 11, reference numeral 10.8 indicates a building block which is generally similar to the building block 10 of Figure l, the same reference numerals being used to indicate the same or similar parts. The block 10.8 differs from the block 10 in that, instead of having a vertical groove 20 at one end and a vertical tongue 22 at the other, it has a vertical groove 20 at each of its ends. This makes the block reversible and also makes it suitable for use in a position where either end thereof is adjacent the vertical side of a door or window opening. The vertically aligned grooves of blocks in superimposed courses can then serve to locate the door or window frame.

The blocks described herein with reference to the drawings can be dry-stacked, reinforcing rods inserted into at least some of the cavities 18 so that the rods span several courses, and the cavities then filled with a cement or concrete mix which, when set and hardened, will have the effect of bonding the blocks together and thereby stabilise the wall.