CHAPTER V 



OPENINGS IN WALLS — ARCHES, LINTELS — WINDOW SILLS— CORBELLING — 

 OFF-SETS — COPINGS — ATTACHMENT OF WOODWOEK TO BRICKWORK 

 AND MASONRY— FIREPLACES — CHIMNEY SHAFTS AND FLUES 



Openings in Walls for Windows, Doors, etc.— The jambs of these openings 

 are finished in return bond as already explained. Openings in walls may- 

 be bridged either by an Cr 

 arch or a lintel. The i s ft 

 terms used in connection 

 with arches are illustrated 

 by Fig. 34, and are as 

 mentioned in the follow- 

 ing paragraph. 



The arch ring is built 

 up of voussoirs, V. The 

 voussoir K is called the 

 keg stone. The ends of 



the arch ring rest on skew-backs, which are the sloping surfaces Sfc, S&, 

 formed on the abutments AA. The lower surface (concave downwards) 

 of the arch ring is called the intrados or soffit, I. The lines in which 

 the intrados intersects the jambs, JJ, are called the springings, Sp, Sp. 

 The outer surface (convex upwards) of the arch ring is called the extrados 

 or back, E. The highest portion of the extrados is the crown, Cr, and 

 the lower portions from A 2 to B 2 , and from A x to Bi, are the haunches. 

 R is the rise of the arch, and C the centre. The masonry, SS, between 

 the extrados and the broken lines, forms the spandrils. 



Brick Arches. — In farm work, brick arches are generally built of uncut 

 bricks ; that is to say, the bricks are not chipped, or cut with an axe, or 

 rubbed to the required wedge- shape. This wedge-shape, either of the 

 voussoirs or of the mortar joints between them, is an essential feature of 

 the arch. When uncut bricks are used, it is the mortar joints (as will 



