A properly installed greenhouse film fixing system keeps the polythene firmly attached to the steel structure, reduces movement caused by wind and makes it easier to replace the covering when it becomes old or damaged.
An aluminium profile is fixed to the greenhouse frame, the greenhouse film is positioned over the channel, and a flexible wiggle wire is inserted into the profile. The wire locks the film firmly into place.
Securing Greenhouse Film to Steel Frames
The main purpose of a greenhouse film fixing system is to create a strong connection between the greenhouse covering and the steel frame.
Greenhouse polythene is relatively flexible. When exposed to wind, it can move if it is not properly secured. Continuous movement can eventually cause tearing, stretching or pulling around the edges.
A profile and wiggle-wire system spread the holding pressure along the length of the greenhouse instead of concentrating it at a few fixing points.
Main Components of a Greenhouse Film Fixing System
| Component | Function |
| Greenhouse polythene sheet | Protects crops from weather |
| Aluminium locking channel | Holds the film along the frame |
| Wiggle wire/spring wire | Locks the film into the channel |
| Steel frame | Supports the greenhouse structure |
| Screws or bolts | Attach the profile to the frame |
| Corner accessories | Complete fixing around corners |
Aluminium Locking Channels: Specifications and Sizes
Aluminium locking channels are special greenhouse profiles designed to hold plastic film. The profile has a groove that accommodates the wiggle wire. Once the film is placed over the channel, the wire is inserted into the groove and presses the film against the profile.
Aluminium is commonly used because it is lightweight, easy to handle and naturally resistant to corrosion compared with ordinary untreated steel.
Common Profile Specifications
Exact dimensions differ between manufacturers, but greenhouse profiles are commonly supplied in different lengths and channel designs.
| Specification | Common Description |
| Material | Aluminium |
| Length | Often 4–6 metres |
| Application | Roof, sides and ends |
| Fixing | Screws or bolts |
| Locking component | Wiggle/spring wire |
| Surface | Mill finish or coated finish |
Profile Length
Longer profiles reduce the number of joints needed. The profile should also be properly aligned with the greenhouse frame. Bending or twisting the profile during installation can affect how well the wiggle wire locks.
Wiggle Wires (Spring Profiles): Tension Ratings
A wiggle wire is a spring-shaped steel wire designed to lock greenhouse film inside an aluminium profile.
Why Wiggle Wire Is Important
A good wiggle wire helps:
- Hold the film securely.
- Distribute tension evenly.
- Reduce film movement.
- Improve wind resistance.
- Make film replacement easier.
- Provide a clean finish.
The holding strength depends on more than the wire itself. It is influenced by:
- Wire diameter.
- Steel quality.
- Galvanising or protective coating.
- Profile design.
- Channel dimensions.
- Film thickness.
- Quality of installation.
- Wind conditions.
Galvanised Wiggle Wire
Galvanised spring wire is commonly preferred for greenhouse applications because it provides better resistance against rust. This is especially useful in areas where the greenhouse is exposed to moisture and rainfall.
| Wiggle Wire Feature | Importance |
| Galvanised finish | Reduces corrosion |
| Correct diameter | Ensures proper locking |
| Flexible spring design | Makes installation easier |
| Good tensile strength | Improves film retention |
| Correct profile compatibility | Prevents poor locking |
Installation: Securing Film in Profiles
1: Inspect the Steel Frame- Before installing the film, inspect the greenhouse frame carefully.Look for sharp metal edges, protruding screws, poor welds, rust, loose frames and bent sections.Sharp edges should be corrected because they can puncture the film.The frame should be clean and ready before covering begins.
2: Fix the Aluminium Profile- The profile is attached to the steel frame using suitable screws or bolts.It should follow the frame evenly without unnecessary bends.Profiles are commonly installed around the areas where the greenhouse film will terminate.
3: Position the Film- The greenhouse polythene is then placed over the frame.Large sheets are easier to handle when several people work together.Installation during strong winds should be avoided because the film can behave like a sail and become difficult to control.
4: Place the Film Over the Profile-The edge of the film is placed over the aluminium channel.There should be enough film allowance for proper fixing.Do not leave only a very narrow section inside the profile.
5: Insert the Wiggle Wire- The spring wire is then pushed into the profile over the film.Work gradually from one end towards the other.The wire should lock the film without cutting or damaging it.
6: Inspect the Finished Fixing- After installation, check the entire fixing line i.e. Loose sections,uneven tension, Film pulled out of the channel, Gaps, Damaged film and Loose screws.Any problem should be corrected before strong winds occur.
Correct Film Tension
The greenhouse film should be reasonably tight, but it should not be stretched excessively. Too much tension can increase stress on the film and fixing points. Too little tension allows the film to flap. Temperature also affects greenhouse film. Plastic expands and contracts as temperatures change. The fixing system should therefore hold the film firmly while allowing normal movement.
Securing Roof and Side Film
Roof sections require careful fixing because they are exposed to wind and weather. Profiles should be properly secured along roof edges and other termination points. Side walls can use fixed film or roll-up ventilation systems.
Where roll-up sides are used, the film fixing arrangement needs to allow the intended movement. A section that is designed to roll up should not be permanently locked in a way that prevents ventilation. This is why the film fixing system should be considered during greenhouse design.
Cost of Profiles and Locking Channel Assemblies
Factors affecting the price include:
- Aluminium profile thickness.
- Profile length.
- Profile design.
- Wiggle wire quality.
- Galvanisation.
- Quantity purchased.
- Supplier.
- Transport costs.
For budgeting purposes, indicative prices in Kenya may fall within the following ranges:
| Component | Indicative Price per four meters |
| Aluminium locking profile | Kshs 500 |
| Wiggle/spring wire | Kshs 50 |
| Profile + wiggle wire | Kshs 550 |
Why a Good Fixing System Extends Film Performance
A good greenhouse film fixing system can help reduce mechanical damage to the covering. A continuous aluminium profile and wiggle wire helps distribute the holding pressure across the film edge.
When film is loose, wind can cause repeated flapping. This movement may eventually produce:
- Small tears.
- Enlarged holes.
- Loose edges.
- Film separation.
- Premature damage.
Maintenance of Profiles and Wiggle Wires
Regular inspection helps identify problems before they become expensive repairs.
Farmers should inspect the fixing system for:
- Loose screws.
- Damaged profiles.
- Bent channels.
- Rusted spring wires.
- Loose film.
- Dirt inside channels.
- Torn film.
Choosing a Greenhouse Film Fixing System for Kenyan Conditions
Different parts of Kenya present different conditions.
In windy locations, the fixing system should be strong enough to withstand local wind exposure.
In areas with frequent rainfall or high humidity, corrosion-resistant components are preferable.
In hot areas, proper film tension and ventilation should be considered together.
For commercial farms, it is worth investing in a complete system rather than mixing incompatible components.
| Farm Condition | Main Consideration |
| Strong winds | Strong profile and secure frame |
| High rainfall | Corrosion-resistant components |
| Hot climate | Proper ventilation and film tension |
| Commercial greenhouse | Continuous profile fixing |
| Small greenhouse | Simple compatible system |
| Frequent film replacement | Reusable profile and wire |
Factors considered when purchasing Greenhouse Profiles and Wiggle Wire
Profile Material- Aluminium is a popular option for its low weight and corrosion resistance.
Profile Dimensions- Check the channel width and depth.
Wire Compatibility- Make sure the wiggle wire is designed for the selected profile.
Profile Length- Choose lengths that are practical for transport and installation.
Film Compatibility- Check that the fixing system is suitable for the thickness of the greenhouse polythene sheet.
Fasteners- Ensure the correct screws or bolts are available for fixing the profile to the frame.
Quantity- Calculate the complete fixing requirement before ordering to avoid shortages during installation.