108 



BRICKWORK. 



be laid directly upon it, but otherwise the use 

 of concrete is advisable. Concrete for this 

 purpose is composed of lime or cement mixed 

 with sand and ballast. In heavy work, Portland 

 or Rosendale cement is generally preferred. 



Bricks being absorbent, the moisture from 

 the ground will frequently rise by capillary 

 attraction. To prevent this, damp courses are 



SILVERLOCK'S HOLLOW BOND. 



employed. These consist of a layer of some 

 material impervious to moisture, which is laid 

 immediately above the ground-line. Asphalt, 

 sheet-lead, slate, and Portland cement are 

 among the materials employed for the pur- 

 pose. To prevent the penetration of wa- 

 ter into the interior of a building, it is fre- 

 quently advisable to construct an area -wall 

 around the entire site, at a distance from the 

 main walls of the building of about three 

 inches. Such walls are built wholly below 

 the ground, and are finished on top with a 

 course of molded bricks. With the same ob- 

 ject, the main walls of isolated buildings are 

 sometimes constructed with a cavity in the in- 

 terior, which not only effectually prevents the 

 dampness from penetrating into the building, 

 but also assists in rendering it warmer in 

 winter and cooler in summer. Such walls, 

 known by the general term of " hollow walls," 

 are constructed of two casings about two inches 

 apart, such casings being connected by the in- 

 sertion of iron or brick ties every two or three 

 feet. The ties are always formed in such a 

 manner as to prevent the passing of moisture 

 across them. At the bottom of the cavity in 

 these walls is a gutter connected with the 

 drain, and any water that finds its way through 

 the outer casing is conducted away. 



Hollow bond, as distinguished from hollow 

 walls, is used in some parts of the country for 

 the erection of small buildings, fence-walls, 

 and in other positions where but little strength 

 is required. There are two methods of con- 

 structing such walls, known respectively as 

 Silverlock's and Dearne's, and both of these 

 systems are limited in their application to 

 walls of the thickness of a single brick. In 



Silverlock's bond the bricks are all laid on 

 edge, stretcher and header alternately in each 

 course, producing an appearance somewhat 

 similar to that of Flemish bond in solid brick- 

 work. Dearne's plan is to lay the bricks all 

 headers and flat in one course, and all 

 stretchers on edge in the other. The only ad- 

 vantage of hollow bond is the saving in ma- 

 terial. Besides these bonds or systems of lay- 

 ing the bricks, there are others in common 

 use. Diagonal bond is sometimes employed 



SEMICIRCULAR ROUGH ARCH. 



in executing thick walls for heavy buildings. 

 On the exterior it is similar to English bond ; 

 but on the interior the bricks are laid di- 

 agonally, with the object of obtaining a bet- 

 ter bond. For the purpose of tying together 

 the component parts of brick walls of all 

 kinds, hoop-iron bond is sometimes employed. 

 In England its use is common, but in the 

 United States it is not employed to any great 

 extent. The hoop-iron is laid in between the 

 mortar-joints, in every fifth or seventh course, 

 and is lapped at all corners and joints. To pre- 

 vent oxidization the iron is often covered with 



EQUILATERAL GAUGED ARCH. 



tar, or is galvanized. Sometimes it has jagged 

 edges to give it a better hold on the mortar. 



The construction of arches in brick may be 

 divided into two distinct classes: 1. Those 

 known as gauged, in which each brick is cut 

 or gauged to a wedge shape in order to pro- 

 duce a parallel mortar-joint, and in which the 

 ends are curved to conform to the curve of 

 the arch ; 2. Those known as rough arches, in 



