Glasshouse Building 223 



between the grains of sand. When ground clinker is used no sand is 

 wanted, as the clinker is fine enough; and as this substance forms a very 

 tough concrete, 8 parts of ground clinker to 1 part of cement will be a 

 good mixture. When calculating out the quantities, allowance must be 

 made for shrinkage. Ground clinker will occupy about one- sixth less 

 space when mixed and put in place than it will when dry, while beach 

 may be calculated as beach alone, the spaces between the stones taking 

 up all the sand and cement. The shrinkage of other materials had better 

 be ascertained by trial of a small quantity before ordering the bulk. The 

 best way to measure the materials is to make a box of 1^ cub. ft. capacity, 

 i.e. measuring 1 ft. 6 in. by 1 ft. by 1 ft. Nine of these boxes full makes 

 just \ cub. yd., and this is a handy quantity to mix up at a time. Of course, 

 when the proportions are 1 in 8, as for the beach and broken brick, the 

 quantity is just short of | yd. 



If the box is treated as one part, no mistake can be made. The 

 materials are shot in a heap on the platform and turned over twice dry 

 to mix them. They are then spread out over the platform and water 

 added through a fine rose, while Canterbury hoes are raked backwards 

 and forwards through the mixture till it seems fairly wet. The mass is 

 then turned up into a lump again, water being added whenever a dry 

 portion shows, the lump being worked all the time with a Canterbury 

 hoe as before. If not wet enough then, it must be turned once more. The 

 finished product should be neither too wet, so as to be sloppy, nor too dry, 

 so as to be solid. The concrete is wheeled to the mould and shovelled in. 

 The first layer may be shot off the shovel with some force, so as to make 

 it spread out beyond the boards, any space that is not so filled being filled 

 up from outside up to the lower edge of the first board. As the work 

 proceeds the louvre boxes are put in, well bedded in, and fixed by a couple 

 of nails lightly driven through the boards. These louvre boxes are made 

 with the sides projecting beyond the ends, for building into brickwork, &c., 

 and for concrete work these projections had better have a V cut in them 

 and have the concrete worked into the V when they are set in the wall. 

 As the concrete rises to the top of the planks the plate ties must be put in. 

 These are simply pieces of flat iron 1 ft. long by 1 in. by \ in. thick, bent at 

 right angles, with one arm 4 in. and the other 8 in., and a f -in. hole punched 

 near the end of the longer arm. These are put in at every 10 ft., and 

 always one at each corner or where a door post will come. They are set 

 touching the inside boards of the mould, and the hole should be about 

 1| in. above the top of the wall when the concrete is filled right up. The 

 top of the wall is best finished off with a builder's trowel, being nicely 

 smoothed down. The concrete should be left alone for twenty-four hours, 

 and then the little crosspieces are unscrewed, the posts taken out till the 

 last few feet of finished wall are reached, and the planks lifted out, 

 scraped clean, especially along the edges, and placed in position farther 

 along and filled with concrete as before. When putting the planks in 

 place it is best to arrange them so that the ends all come in different 



