The following are several common shapes of frames;
Quonset- sidewall height is low, which restricts storage space and headroom.
Gothic: The gothic frame construction is similar to that of the Quonset but it has a gothic shape (Figure 3). Wooden arches may be used and joined at the ridge. The gothic shape allows more headroom at the sidewall than does the Quonset.
Rigid-frame: The rigid-frame structure has vertical sidewalls and rafters for a clear-span construction. There are no columns or trusses to support the roof. Glued or nailed plywood gussets connect the sidewall supports to the rafters to make one rigid frame. The conventional gable roof and sidewalls allow maximum interior space and air circulation. A good foundation is required to support the lateral load on the sidewalls.
Post and rafter and A-frame: The post and rafter is a simple construction of an embedded post and rafters, but it requires more wood or metal than some other designs. Strong sidewall posts and deep post embedment are required to withstand outward rafter forces and wind pressures. Like the rigid frame, the post and rafter design allows more space along the sidewalls and efficient air circulation. The A-frame is similar to the post and rafter construction except that a collar beam ties the upper parts of the rafters together.
Ridge and furrow (gutter connected) green houses:
A green house with more than three bays (multi gutter connected) is called a ‘range’
The lowest cost per square foot of growing space is generally available in a freestanding or even-span greenhouse that is 17 to 18 feet wide. It can house a central bench, two side benches, and two walkways. The ratio of cost to the usable growing space is good.
When deciding on the type of structure, be sure to plan for adequate bench space, storage space, and room for future expansion. Large greenhouses are easier to manage because temperatures in small greenhouses fluctuate more rapidly. Small greenhouses have a large exposed area through which heat is lost or gained, and the air volume inside is relatively small; therefore, the air temperature changes quickly in a small greenhouse.
- Sawdust/Sand/Manure at the ratio of 3:1:1 Or
- topsoil/sawdust/manure/sand/charcoal dust at the ratio of 10:10:6:5:3 Or
- top soil/sand/manure at ratio of 3:1:1
- Note: A lorry of each (7 tons) is required
- Other materials used as growing media are: Peat, perlite,bark,vermiculite
Sterilization of Growing Media:
Water the media in the beds thoroughly and then cover with black polythene paper for three-four weeks to eliminate weed seed, disease pathogens and insect pests in the growing media. The media also becomes cured and compacted ready for planting.