Building system

A building unit combination comprising:

• a building block interlocked with a building block end unit, the building block being able to interlock with a further, similar building block, the building block end unit of the combination comprising:
• a wall portion having a flat outer surface, an inner surface and a predetermined width;
• a flat end surface;
• a first hollow projection extending from the inner surface of the wall portion, the projection comprising a narrow portion adjacent the inner surface and a wider portion extending from the narrow portion;
• a second hollow projection extending from the inner wall and defined at one side by the flat end surface of the end unit, and at the other side by a wall remote from the end wall and comprising a first web extending outwardly from the inner surface of the wall portion and a second web, attached to the first web, and spaced further from the end surface than the first web;
• a recess formed on the second projection, remote from the outer surface of the wall portion and the flat end surface and comprising a first surface, generally parallel to the inner surface of the wall portion and an end surface, generally parallel to the end wall;
• a space defined between said first and second projections;
• the building block comprising a wall portion having a flat outer surface, an inner surface and a predetermined width equal to the predetermined width of the wall portion of the end unit;
• at least one hollow projection extending from the inner surface of the wall portion, corresponding to the first projection on the end unit, and comprising a narrow portion adjacent the inner surface of the wall portion and a wider portion extending from the narrow portion, said at least one hollow projection engaging the space defined between the first and second projections of the end unit to interlock said building block and said end unit, the width of the wide portion being substantially equal to the distance between the narrow portion of the first projection of the end unit and the first web of the second projection and the width of the narrow portion being substantially equal to the distance between the wide portion of the first projection and the second web of the second projection;
• the wall portion having an extension at each end extending beyond the said at least one hollow projection of the building block by an amount substantially equal to half the width of a wider portion;
• and
• the recess of the corner unit receiving one said wall portion extension of the building block.