Greenhouse Construction is taking shape under new modernised farming. Unlike open-field farming, a greenhouse protects crops from excessive rainfall, strong winds, pests, and sudden temperature changes. This controlled environment enables farmers to produce healthier crops with better yields and improved quality.
A well-planned greenhouse should be strong enough to withstand local weather conditions while providing adequate ventilation, proper light distribution, and efficient water management. Every stage of construction, from selecting the site to installing the greenhouse cover, contributes to the overall performance of the structure.
Site Selection and Soil Testing before conducting Greenhouse Construction
1. Location-An ideal greenhouse site should have:
- Good sunlight throughout the day.
- Reliable water supply.
- Well-drained soil.
- Easy access for vehicles and workers.
- Protection from strong winds where possible.
- Enough space for future expansion.
Avoid constructing greenhouses in areas that remain waterlogged after rainfall, as excess moisture around the foundation can weaken the structure over time.
2.Water Availability-A greenhouse depends almost entirely on irrigation because rainfall does not reach the crops inside the structure.Before construction begins, farmers should identify a reliable water source such as: boreholes, wells, water storage tanks etc. Adequate water storage is especially important during dry seasons when demand for irrigation increases.
3.Accessibility- The greenhouse should be easy to access throughout the year on terms of proximity and infrastructure. It eases transport of commodities, harvest collection and movements.
4.Soil Testing Before Construction- It involves knowing the soil Ph, texture, nutrient levels, and drainage characteristics.
Site Survey and Marking
Before excavation begins, builders should measure and mark the greenhouse layout carefully. Important measurements include:
- Length.
- Width.
- Door position.
- Ventilation openings.
- Foundation points.
Using measuring tapes, pegs, and builder’s lines helps maintain accurate alignment throughout construction.
Proper marking also simplifies the installation of structural members during later stages.
Preparing for Foundation Construction
Once the site has been selected, tested, and cleared, the next stage involves preparing the foundation that will support the greenhouse frame. The type of foundation depends on:
- Soil conditions.
- Greenhouse size.
- Structural design.
- Wind conditions.
- Budget.
A strong foundation distributes the weight of the greenhouse evenly while resisting movement caused by wind and changing soil conditions. Proper foundations are the first step toward building a greenhouse that remains stable for many years.
Building Strong Foundations (Concrete vs Earth Anchor)
While the greenhouse frame carries the weight of the structure, the foundation transfers this weight to the ground and keeps the greenhouse stable during strong winds and heavy rains.
Purpose of a Greenhouse Foundation
- Supports the weight of the greenhouse frame.
- Prevents movement during strong winds.
- Keeps the structure level.
- Reduce stress on the steel or timber frame.
- Improves the lifespan of the greenhouse.
- Maintains proper alignment of doors and ventilation openings.
Without a stable foundation, the greenhouse frame may gradually shift, causing the greenhouse cover to loosen or tear.
Concrete Foundations
Concrete foundations are widely used for permanent greenhouse structures; especially metallic greenhouses intended for commercial farming. The process involves excavating foundation holes, positioning anchor posts or base plates, and filling the holes with concrete. Once the concrete cures, it forms a solid base that securely holds the greenhouse frame.
Advantages of Concrete Foundations
- Excellent structural stability.
- High resistance to strong winds.
- Suitable for large greenhouses.
- Long service life.
- Low maintenance.
Concrete foundations are particularly suitable for areas with unstable soils or regions that experience strong winds.
Earth Anchor Foundations
Earth anchors provide an alternative foundation system for certain greenhouse designs.
Advantages of Earth Anchors
- Faster installation.
- Lower labour requirements.
- Minimal excavation.
- Reduced concrete use.
- Easier relocation if required.
Frame Assembly: Hoops, Purlins, and Tension Braces
The frame forms the structural skeleton of the greenhouse and supports every other component, including the greenhouse cover, insect netting, irrigation lines, and crop support systems.
Hoops
Hoops are the curved structural members that create the characteristic arch of the greenhouse. They extend from one side of the foundation to the other, forming the roof and side walls. The number of hoops depends on the greenhouse length and structural design.
Functions of Hoops
- Support the greenhouse roof.
- Carry the weight of the greenhouse cover.
- Resist wind loads.
- Maintain the overall shape of the greenhouse.
Hoop Installation
Each hoop should be securely connected to the foundation before additional structural members are installed. Builders should check:
- Vertical alignment.
- Equal spacing.
- Secure fastening.
- Correct height.
Purlins
Purlins are horizontal members that connect adjacent hoops. They increase the strength of the greenhouse by preventing individual hoops from moving independently. Without purlins, the greenhouse frame would be less stable under wind loads.
Functions of Purlins
- Connect all hoops.
- Improve structural rigidity.
- Support greenhouse film.
- Maintain roof alignment.
- Distribute loads evenly.
Most greenhouse designs include ridge purlins along the roof and side purlins along the walls.
Tension Braces
Tension braces strengthen the greenhouse by resisting sideways movement. They are usually installed diagonally between structural members. Strong winds create horizontal forces that can twist or distort the greenhouse frame. They reduce these movements by increasing the rigidity of the structure.
Benefits of Tension Braces
- Improve wind resistance.
- Prevent frame twisting.
- Reduce structural vibration.
- Increase overall stability.
- Extend greenhouse lifespan.
Alignment During Frame Assembly
Throughout construction, builders should regularly check the alignment of the frame.
Important checks include:
- Straight side walls.
- Uniform hoop spacing.
- Level ridge line.
- Secure bolt connections.
- Correct brace installation.
Small alignment errors become more noticeable when installing greenhouse film, making early correction essential.
Fasteners and Connections
The strength of a greenhouse depends not only on the structural members but also on the quality of the connections between them.
Common fastening materials include:
- Galvanized bolts.
- Nuts.
- Washers.
- Self-drilling screws.
- Steel brackets.
Using corrosion-resistant fasteners helps maintain structural integrity for many years.
Loose connections should be tightened before the greenhouse cover is installed.
Installing Greenhouse Polythene Film and Insect Netting
Installation should preferably be carried out on a calm day with little or no wind. Strong winds make it difficult to stretch the greenhouse film evenly and may damage the material during installation.
1.Greenhouse Polythene Film
Greenhouse polythene is a specially manufactured plastic cover designed to withstand outdoor weather conditions while allowing enough sunlight to reach the crops. Unlike ordinary plastic sheets, greenhouse film is treated to resist ultraviolet (UV) radiation, which helps extend its lifespan.
A quality greenhouse film performs several functions:
- Allows sufficient light for photosynthesis.
- Protects crops from rainfall.
- Reduces the effects of strong winds.
- Helps maintain suitable temperatures.
- Minimises excessive moisture loss.
Most commercial greenhouse films also include additives that improve durability and reduce the formation of water droplets on the inside surface.
2.Preparing the Frame Before Installation
Before the greenhouse cover is installed, inspect the frame carefully. Check for:
- Sharp metal edges.
- Protruding bolts or screws.
- Loose fasteners.
- Rough welds.
- Damaged structural members.
Sharp edges can puncture the greenhouse film during installation or as the structure expands and contracts with changing temperatures. Where necessary, cover exposed sharp points using protective tape or plastic caps.
3.Positioning the Greenhouse Film
The greenhouse film should be unfolded carefully to avoid unnecessary stretching or tearing. Installation usually begins from one end of the greenhouse before gradually pulling the film across the roof. During this process:
- Avoid dragging the film across rough surfaces.
- Keep the material clean.
- Ensure the film remains centred.
- Prevent twisting during installation.
Uniform positioning makes tensioning easier and improves the appearance of the finished greenhouse.
4.Applying Correct Film Tension
Correct tension is essential for maintaining the strength and durability of the greenhouse cover. If the film is too loose:
- Wind causes excessive movement.
- The material wears more quickly.
- Rainwater may collect on the roof.
- Noise increases during windy weather.
If the film is stretched too tightly:
- The material may tear.
- Expansion during hot weather becomes restricted.
- The lifespan of the cover may be reduced.
The film should be firm enough to remain stable while still allowing for normal expansion and contraction caused by temperature changes.
Installing Insect Netting
Ventilation is necessary to regulate temperature and humidity inside the greenhouse. However, open ventilation also creates entry points for insects that can spread diseases and damage crops. Insect-proof netting allows fresh air to enter while reducing pest entry.
1.Positioning the Insect Net
The insect net is normally installed on:
- Side ventilation openings.
- End-wall ventilation sections.
- Roof vents where applicable.
Importance of Proper Ventilation
- Reducing excessive heat.
- Lowering humidity.
- Improving air circulation.
- Supporting healthy plant growth.
- Reducing fungal diseases.
Securing Film in Aluminium Profile Channels
Lock channels are fixed to the greenhouse frame and hold the greenhouse film securely using spring wire, also known as wiggle wire.
This system provides a strong and durable method of fastening while allowing easy replacement of greenhouse covers when necessary.
Aluminium Profile Channels
Aluminium profile channels are lightweight, corrosion-resistant components installed along the roof edges, side walls, end walls, door frames and ventilation openings.
Benefits of Aluminium Profile Channels
- Strong attachment of greenhouse film.
- Long service life.
- Easy removal during film replacement.
- Excellent resistance to corrosion.
- Uniform tension across the greenhouse.
Wiggle Wire Installation
Wiggle wire is inserted into the aluminium profile channel after the greenhouse film has been positioned. The wire presses the film firmly into the channel, creating a secure connection that withstands wind and changing weather conditions.
Advantages of wiggle wire include:
- Reusable for several film replacements.
- Simple installation.
- Strong holding capacity.
- Even distribution of pressure.
Inspecting the Installed Cover
After installation, inspect the greenhouse thoroughly. Confirm that:
- The greenhouse film is evenly tensioned.
- No wrinkles are present.
- Wiggle wire is fully inserted.
- Insect netting is tightly secured.
- Doors open and close correctly.
- Ventilation openings function properly.
- No sharp edges are touching the cover.