BUILDING CONSTRUCTION 185 



For agricultural buildings two classes of damp-resisting course- 

 can be recommended. They are (a) a layer of British or liquid 

 asphalt about f inch thick, poured in a hot liquid state upon the 

 walls. This is composed mainly of Archangel tar, a percentage 

 of pitch, and thinned to the proper consistency with a coal tar oil. 

 It should be neither too brittle nor too soft. If the former, it is 

 easily cracked and becomes useless, and if too soft it squeezes out 

 when the weight of the building comes upon it; (b) a ready-made 

 rolled damp-resisting course of good quality will be found more 

 serviceable, more reliable, less easily misapplied and certainly much 

 quicker in execution, as no boiler is involved and the work may be 

 stopped at any stage and renewed when found necessary. Many 

 types of such courses are available, a bituminous sheeting with a 

 good canvas core being the best. There are many other types 

 of damp-resisting courses, but they are hardly suitable for agricul- 

 tural work, either by reason of their nature or their cost. Some- 

 times, in slate-producing districts, effective courses are made from 

 thick slates embedded in cement mortar. These need to be in two 

 or three layers, with all joints broken bonded. In any case, their 

 great fault is that they are full of joints. Mineral rock asphalt^ 

 or Limmer rock asphalt, is very satisfactory, but is too expensive 

 for anything but high-class buildings. Glazed earthenware tiles 

 are occasionally used. These are specially made for the purpose, 

 and are sometimes perforated in order to act as ventilators for 

 wooden floors. They should be embedded and jointed in fine 

 Portland cement as closely as possible. They are open to objection 

 by reason of their joints, and in any case are too expensive for 

 ordinary agricultural work. 



Retaining Walls. On some sites it is impossible to avoid the 

 ground being higher than the floor level at one or more sides of the 

 building, and where this state of matters exists the wall supporting 

 the high soil is known as a " retaining wall." In such cases the 

 earth or rock should not come in direct contact with the wall of the 

 building, otherwise it will be impossible to prevent surface water 

 and subsoil water running from the higher ground to the retaining 

 wall, which will act as a dam and consequently be constantly in a 

 wet state. There are various methods of preventing or curing such 

 dampness. The simplest is to form a trench down to the level of 

 the bottom of the foundation, laying a field drain with proper runs 

 and outlet at the bottom, and filling up the whole space with clean, 

 dry, broken stones or bricks, which should be carefully hand-packed. 

 The top of these stones at the ground level should be covered with 

 cement concrete, extending the full width of the trench. An 



