252 GREENHOUSES 



forms, usually vertically, about midway be- 

 tween the sides and 2 or 3 feet apart before 

 the concrete is poured. 



When an extra strong wall is required rods 

 may be laid horizontally on the top of every 

 layer or every second layer as the concrete is 

 placed and tamped down into the soft mix- 

 ture. When the walls extend only 3 or 4 feet 

 above the surface and are at least 8 inches 

 thick as is commonly the case in greenhouses, 

 little if any reinforcement is needed. 



Walks and Floors. Concrete walks are 

 now very commonly used in commercial as 

 well as private greenhouses, and the boiler 

 and service rooms are usually floored with 

 concrete. As the walks are not usually sub- 

 ject to as hard usage as those laid out-of- 

 doors, or to the action of frosts, it is not 

 necessary to make them quite as thick, but in 

 other respects they differ but little from the 

 concrete sidewalks now so common. 



The common method of building walks in 

 a greenhouse is to make an excavation a few 

 inches deep and as wide as the walk is to be 

 and fill it with broken stone, pieces of brick, 

 etc., to make a foundation. On top of this, 

 two pieces of straight 2 x 4-inch lumber are 

 placed on edge, level with each other and 



