WINDOW SILLS 47 



If a window be at all exposed to the weather a water -bar is fitted, 

 consisting of an iron bar embedded half in the wooden sill of the 

 window frame and half in the concrete or brick sill. Concrete sills are 

 moulded in place ; brick sills are built in cement mortar. 



Referring to Fig. 41 the use of a throat, or groove, in both wooden 

 and concrete sills will be noted. A throat throws off rain-water, which 

 would otherwise find its way along the under surface of a sill. A similar 

 groove is formed in the plaster with which a brick sill is rendered. 



The top of a window sill should be sloped, or weathered as it is 

 called, from A to B (Fig. 41), so as to throw off the rain-water. Note 

 how the slope is carried back for about 1\ inches below the wooden 

 sill. This, in conjunction with the throat T, tends to prevent the 

 penetration of water into the joint between the wooden and the concrete 

 (or brick) sills. 



The window shown in Fig. 41 is provided with a window-board, 

 lining, and architrave, as marked on the figure. These, of course, 

 would be omitted in the case of stable buildings, etc. 



If a sill consists of one stone which, as is usually the case, is built 

 in during the progress of the brickwork, it should bear on the brick- 

 work for about 3 inches of its length at each end only, a space of 

 about £ inch being left below the intermediate portion. The reason 

 for this is that, on account of the superior weight of the jambs, the 

 settlement of the brickwork under each end of the sill is greater than 

 that of the brickwork under the middle of the sill. Consequently, 

 if the sill bore hard on the brickwork below the middle of its length, 

 it would be bent convex upwards as settlement proceeded, and would 

 probably fracture at or about mid-length. 



The same precaution should be observed in the case of concrete 

 sills. A board should be placed below the space which the sill is to 

 occupy. This board should be slightly wedged up upon the brick- 

 work, and should extend to within 3 inches of each end of the sill. 

 The sill is moulded on top of the board, and as soon as the concrete 

 has set sufficiently the board should be removed. Its removal is 

 easily effected by first removing the small wedges underneath it. In 

 this way a space is left between sill and brickwork, all along the 

 length of the former with the exception of 3 inches at each end. 

 When the building has reached the pointing stage, this space may be 

 filled up with safety. 



