112 
Labourers' Cottages. 
[may, 
work their somewhat smooth surface provides a poor key for 
plastering. The latter disadvantage may be remedied by a 
wash of cement and coarse sand, but the bricks can now be 
obtained properly grooved or keyed for plastering. 
Foundations. — It frequently happens that the subsoil of 
the selected site is of a character which renders concrete 
under the footings necessary to a depth of 9 in. or 12 in., 
the object being to distribute the superincumbent weight 
over a greater area than would be the case were the walls 
built directly on the soil. If the ground be made-up ground, 
or uneven or variable in its strength, the concrete may also 
have to act as a lintel. Where the subsoil is of rock, chalk, 
gravel, or compact sand, footings may be unnecessary. 
Walls. — Where walls are built of brick a thickness of 9 in. 
is usually prescribed for external walls. In some situations, 
however, particularly those on high ground and exposed to 
the south-west, it has been proved that a 9-in. wall will not 
prevent the damp from penetrating (though the quality of 
the bricks used may account for this in some cases), and in 
such circumstances hollow walls may be adopted. 
Hollow or cavity walls serve two useful purposes : first, 
to preserve a more uniform temperature inside the building ; 
and secondly, to prevent dampness extending from without 
to the interior of the building. The cavity between the walls 
should not exceed 2J in., and should in all cases commence 
from the damp course. Iron ties should be either galvanised 
or tarred and sanded, and inserted at least three to every 
superficial yard, and these not directly over one another, but 
midway between those immediately beneath them. The 
heads of all doors and window openings should be protected 
by means of strips of lead or zinc from any moisture that may 
drain upon them, and should extend 2 in. beyond the ends of 
the woodwork. 
iUthough the useful purposes served by hollow walls are 
obvious, what are known as 11-in. hollow walls are not to 
be recommended, as they involve a sacrifice of strength and 
stability as compared with a 9-in. solid brick wall well and 
properly built in English or Flemish bond. Opinions may 
differ on this point, but it seems obvious that two detached 
4j-in. walls, with no additional bond beyond that of three 
