The building regulations of certain cities require that bond stones shall be used in brick piers of less than a certain size. When such stones are used they should be of some strong variety, and should be cut the full size of the pier. It is also very important that the outside and inside bricks be brought exactly to the same level to receive the stone, for if the stone bears only on the outside bricks the weight will cause them to buckle and separate from the pier, while if the weight is borne by the centre of the pier it is liable to crack through the middle.

Bond stones should not be used in a wall in the manner shown in Fig. 119, as they give the pressure no chance to spread, but keep concentrating it back on the part of the wall immediately under the bond stones, as shown by the short vertical lines.

207 Bond Stones and Templates 100128

Fig. 118.

Bearing stones used under the ends of beams or girders to distribute the weight on the walls are called templates. They should always be of a very hard, strong stone, laminated if it can be obtained, and the thickness of the stone should be one-third of the narrowest dimension of the stone, unless the stone is unnecessarily large, but in no case less than 4 inches. It is always better that templates be too large rather than too small.

The area of the templates should be such that the pressure which it transmits to the wall below shall not exceed 120 pounds per square inch for common brickwork, or 150 pounds for common rubble with flat beds.

It is also a good idea to place a flat stone above the end of a wooden girder, so that the wall will not rest on the wood, which is quite sure to shrink and possibly affect the wall.