I 22 
VEGETABLE GARDENING 
pairs in other types of construction. With proper care 
and painting the wood parts in a well-built house will 
last 25 years, and they could then be renewed at a cost 
which would not be burdensome to a grower who had 
harvested profitable crops for a quarter of a century. 
Iron pipe or angle irons, concrete, and thoroughly dried 
cypress are the most important materials needed in the 
construction of a modern commercial greenhouse. 
176. Semi-iron type of construction. — This is by far 
the most popular form of construction. The walls are 
usually concrete, and the 2-inch pipe or angle iron posts 
which support the roof of the house are often embedded 
in the concrete. If provision is made for walks or alleys 
along the walls in the greenhouse the posts should ex- 
tend at least 6 feet 4 inches above the ground level. All 
purlins, braces and interior posts are made of iron. The 
construction is of such a character that it is easily pos- 
sible to replace decayed wood parts without disturbing 
the posts, purlins or braces. Walks, beds and benches 
of concrete may be used if desired. Houses of this type 
are attractive, serviceable and durable. Any local carpen- 
ter can build them without difficulty, for nearly all wood 
parts are cut to the right dimensions at the factory and 
blue prints are furnished for the instruction of builders. 
177. Forms of greenhouses. — Lean-to, side-hill, even- 
span and three-quarter span are the distinct forms of 
greenhouse construction. The lean-to house is the least 
expensive type to construct, and it is often highly sat- 
isfactory ; but it is most useful when built as a lean-to 
against a building or wall running southwest and north- 
east, where there will be practically no shading of the 
plants. Lean-to houses are sometimes built along the 
south side of larger greenhouses. While simple in con- 
struction, they are not generally popular. 
Side-hill greenhouses are of various styles. Sometimes 
they are built on the ridge and furrow plan with very 
