Poly tunnel design
Poly tunnel designs are very similar they follow the same pattern steel or PVC pipes are bent into semicircular hoops then secured to the ground. Using timber framing to forms the end sections,ground and intermediate supports. Steel supports for the roof ridge pole with a timber cap and steel for an extra vertical central support and external east end supports for the door section. A concrete support for the west door. The doors to be of a timber construction with wire mesh ventilation and a simple lock.
Horticultural grade PVC covering (special ultra-violate coating) to prevent sun damage to be stretched over the structure and secured using timber battens. All surfaces with sharp edges to be covered with tape and all points of contact with the PVC using hot spot tape ( hot spot tape prevents stretching of the PVC covering in hot weather). A brick path to absorb heat and for ease of access. Various wire supports for plants and a pond for climate control, biodiversity and predator habitat.(frogs)
Horticultural grade PVC covering (special ultra-violate coating) to prevent sun damage to be stretched over the structure and secured using timber battens. All surfaces with sharp edges to be covered with tape and all points of contact with the PVC using hot spot tape ( hot spot tape prevents stretching of the PVC covering in hot weather). A brick path to absorb heat and for ease of access. Various wire supports for plants and a pond for climate control, biodiversity and predator habitat.(frogs)
poly tunnel diagram
Limiting Factors
The site is on a hill with strong winds from the west in winter and the water supply cannot be relied on, there is from time to time vandalism and theft. The site access can be a problem in wet conditions as it becomes very muddy. The construction of so many buildings in a short time span has time implications and funding issues.
Resources
This project was planned for next year when we could finance the project however we managed to collect many of the materials and man power in a very short space of time. The resources are listed below.
- PVC piping 50mm x 100m (new) from a closed down builders yard that required clearing.
- Hundreds of bricks both new and recycled from a closed down builders yard that required clearing.
- Concrete posts from a closed down builders yard that required clearing.
- Steel pipe work for the ground spikes from a friend recycled from a factory.
- Steel structure for ridge pole recycled.
- Timber recycled from skips and a school .
- Timber and screws from local merchant . (£60)
- Horticultural PVC covering from specialist suppler.(£130 life span 7-10 years) costs divided between 3.
- Pond and old 400 litre bin (on site when we arrived) pond liner John had spare from another project)
- THE MOST IMPORTANT a group of friends to help with the cover installation.
Analysis
The designs for poly tunnels are straight forward and to a formula which we tweaked to meet the requirements of the site which include extra protection for wind in the form of a shed wind break concrete door enforcing a steel central post and east end door supports. An additional water supply from the mains to the shed and rain water harvesting system from the shed into 2 water cubes of 1000L each.(which will be the primary source) The next phase will be the security of the tunnel, hedging on 2 sides a chicken run connected to the shed in front of the of the tunnel via a gate and fencing on the north aspect will limit the potential for vandalism.
The collection of materials before work commenced and the organization of extra people power will enable a quick build.
The collection of materials before work commenced and the organization of extra people power will enable a quick build.