254 GREENHOUSES 



a very neat walk may be made in this way. 



For the lower layer, when there is a firm 

 foundation, a I '.2^/2 15 mixture will be satis- 

 factory. The top layer should "be of a i :2 14 

 mixture or, when an especially smooth sur- 

 face is required, of a 1 12 mixture, that is, 

 one part of cement and two parts of sand. 



Floors are laid practically the same as 

 walks, except that they are usually troweled 

 level instead of curving. The work is begun 

 at one side of the floor, and as soon as one 

 section has been laid and has had time to 

 set, the side boards are taken up and put 

 down for the next section. Floors should 

 seldom or never be laid in a solid mass. 



Waterproofing. Much trouble is often 

 experienced in underground boiler rooms 

 from water. The- best protection is to lay 

 a row of tile completely around the 

 outside of the foundation, at the bottom, and 

 connect it with the sewer or drain. If the 

 bottom of the cellar is springy it may be 

 necessary to lay the floor in a solid piece and 

 in two layers. After the first layer has set 

 and become dry, or nearly so, a thick coating 

 of hot tar may be applied, allowing it to ex- 

 tend for a few inches up the side walls. 

 When this has hardened put on another coat 



