184 
Hollow Brick Roofn. 
The arches are iormed, as shown, with hollow brick, set in 
good stone lime mortar ; and to render the arch water-tio;ht, and 
prevent absorption by the bricks, they require a coating of 
cement, paint, or pitch — the two former are the most manage- 
able, and calculated to give least trouble. This must be done 
with great care, or heavy rain will come through the roof. 
I append a statement of the cost of a hollow brick roof as 
compared with roofs of timber and slates as used in common 
farm buildings. The following estimate is for one square of 
roofing, or 100 feet superficial : — 
£. s. d. 
Cost of 200 bricks, at 50«. ])er 1000 0 10 0 
Labour in setting arch, &c 056 
Lime mortar required 020 
Iron spring-ers placed 8 feet apart on the building 0 5 0 
Iron tie-rods, including fixing, &c 0-3 0 
Cost of forming parapets for gutters, including all materials ..030 
Stone coping to parapets, or hollow bricks set in cement . . .040 
Forming gutters with Portland cement, including labour, &c. ..028 
Securing the outside of arch from wet, with ])aint 0 3 0 
£1 18 2 
Common roof with Baltic timber, per square 1 10 0 
Welsh slating, per square 140 
Stone coping to ridge 040 
£2 18 0 
In the above calculations the prices actually paid have been 
given, and the most costly mode of constructing the arched roof 
yet adopted has been taken ; for instance, to use lioUow-brick 
coping set in Portland cement for the parapets would reduce the 
item of coping one-lialf. I may also observe, that in districts 
where freestone is plentiful, the adoption of the stone springers, 
instead of the cast-iron ones with parapets and gutters behind, 
might reduce the whole amount very considerably. Tlie hollow 
bricks are made with an ordinary pipe-tile machine. No charge 
has been inserted for carriage, as this varies so much in different 
places, and the comparative cost of the two descriptions of roof 
would be materially altered if the building to be covered were 
at any considerable distance from a yard where hollow bricks 
can be made. 
Robert Dunn. 
Howick, \2th June, 1854. 
