BUILDING CONSTRUCTION 



187 



truss. 



ventilated. Figures 86-88 

 show various systems which 

 may be adopted. 



Rain - Damped IV alls. 

 Walls exposed to the prevailing 

 wet wind are usually damp 

 during the rainy seasons. In 

 new buildings this danger may 

 be provided against by building 

 the wall hollow, covering the 

 outside with a coat of cement 

 plaster waterproofed with a 

 good waterproofing solution, or 

 by covering the outer surface 



of the brick wall with slates or 



... .. , . , , ,, FIG. 89. Plan and elevation of a 12 inch 



shingles nailed to wood laths. thick hollow brick wall with piers 



Hollow brick walls should be outside and occurring at each roof 

 carefully built. The outer thick- 

 ness need not be more than 4| 

 inches if built in cement, the 

 main part of the wall being 

 inside. This arrangement pro- 

 vides a substantial support for 

 the roof, and bears the wear 

 and tear which is constant inside 

 agricultural buildings. The 

 cavity between the outer and inner walls 

 should be about 2\ inches, properly 

 ventilated at the top and bottom, with 

 galvanised louvred gratings to prevent 

 the entry of rain and vermin. Galvan- 

 ised malleable iron ties must be care- 

 fully built between the wall and its 

 outer casing, using at least two ties to 

 every superficial yard of work. These 

 ties have a twist in the middle to pre- 

 vent moisture from travelling across 

 to the inner wall. During the erection 



of hollow walls, care must be taken FIG. 91. Section of hollow 

 that the mortar does not drop down on 

 to the ties nor to the bottom of the 

 cavity. This may be prevented by 

 hanging laths in the cavity, and draw- 



FIG. 90. Plan of 16 inch thick hollow 

 brick wall with piers on inside face. 



brick wall with ventila- 

 tion of cavity by grat- 

 ings. Ties through 

 cavity and the footings 

 and damp-proof course 

 are shown. 



