The present application relates to building blocks such as are used for the construction of walls and other structures. While the invention is described in relation to its application to concrete building blocks, the term building blocks is to be taken to include blocks of all sorts including clay bricks used for building purposes.

Concrete blocks are made in many sizes and shapes. A form of block commonly used has nominal dimensions of 200mm x 200mm x 300mm and has two central cavities which, when the block is in use, pass vertically through the block the cavities being separated by a central web. Looked at from above surface areas are provided on the upper face of the block extending along each side of the block, across the middle of the block between the central cavities and across both ends of the block.

One problem with concrete blocks is the passage of moisture through the blocks. It is believed that this occurs mainly through mortar joining the blocks rather than through the blocks themselves. The object of the present invention is to provide a building block the construction of which is such as to help reduce the passage of moisture through the block and particularly through the mortar joining the blocks by avoiding the provision of any direct mortar connection between two sides of a block and by providing means whereby water entering from outside or condensing within a block will tend to move towards the outer face of a block.

A concrete block according to the invention is of generally parallelopipedal form and consists of a pair of parallel side walls presenting upper and lower longitudinally extending surfaces for the reception of mortar, the side walls being joined by a laterally extending member or members having an upper face or faces extending downwardly from one side wall towards the other, there being no upwardly or downwardly directed mortar

receiving faces extending transversely of the block from one side wall to the other. In a preferred form of construction the block is substantially "N" shaped in side elevation. In order that the nature of the invention may be better understood and put into practice preferred forms thereof are hereinafter described with reference to the accompanying drawings, in which: -

Figure 1 is a perspective view of one form of block according to the invention;

Figure 2 is a cross-sectional view thereof; and Figures 3 to 5 are cross-sectional views of other forms of block according to the invention.

The block illustrated in Figures 1 and 2 is made preferably by casting or extrusion in concrete of a conventional mix and consists of two side walls 10 and 11 which extend longitudinally throughout the length of the block and which present surfaces 12, 13, 14 and 15 which extend the full length of each side wall and are for the reception of mortar. The side walls 10 and 11 are joined by a laterally extending member 16 which has an upper sloping surface 17 that slopes from the side wall 10 down to the side wall 11.

It is to be noted that there are no transverse flat surfaces for the reception of mortar along which moisture could be transferred across the block. In addition to this, moisture entering the block or condensing within the cavity of the block will flow downwardly towards the side wall 11 which in use would be the outer wall of the block, to keep any moisture away from the inner wall 10 of the block.

The forms of the invention shown in Figures 3, 4 and 5 all have similar fetures to that described in connection with the block shown in Figure 2 and will not therefore be described in details, in that the form of construction is

obvious from the drawings.

The blocks as described to this point do not provide for any vertically extending passage through the blocks through which air can circulate to help dry out any moisture passing through the outer face, to permit this the laterally extending member may have a portion removed as illustrated at 18 in Figure 1. In addition, vertical holes may be punched through the laterally extending member of the blocks illustrated to permit the passage of electrical conduit or steel reinforcement throughout the height of a structure built with the blocks.

Blocks according to the invention may be formed in a wide variety of sizes in accordance with standard practice in the industry and may be constructed by standard moulding methods or in the case of blocks of the configuration such as that shown in Figure 2 may be formed by extrusion. Flanges and corresponding grooves may be formed along the edges of the blocks to allow interfitting of each block with the block above and the block below. The forms of the invention described above are given by way of example only a variety of other forms within the general scope of the invention as defined above may be devised. For example, the laterally extending member may extend downwardly from each side wall to a point near the middle of the block and holes formed along the joining line to allow for collection and drainage of any moisture collecting within the block.