Choosing Your Polyhouse
Planning Permission
Planning requirements vary with each individual local authority and location. It is most likely that your proposed structure will require planning permission even in the most basic form of notification.
We do recommend planning permission be achieved prior to purchasing a structure to ensure the correct specification is chosen to meet any specific planning requirements.
We will assist with advice and are happy to produce specific drawings to support your planning application.
Foundations
On structures larger than 14 feet in span, it is essential to have the foundation tubes anchored firmly in concrete. The volume of concrete required to set foundation tubes increases proportionally to the span size of the structure, we can advise the volume and specification of ballast accordingly. Foundation tubes can be supplied ahead of a structure to be delivered for early site preparation upon request.
Cladding Systems
Three methods of affixing cladding material to the structure are available : -
Trench & Bury a low cost traditional method for smaller tunnels where a trench is dug a spade deep and a spade wide for the polythene to be laid in and back-filled with the spoil, following this the hoops are raised to tension the polythene. This method offers limited flexibility especially if digging is difficult or the structure is long.
Timber rail for ground, side & end rails - a tanalised timber rail is joined with splice plates and attached to the structure at each hoop with pressings secured by through bolts. The polythene cladding is wrapped around a timber batten which is then nailed to the timber rail where it can be tensioned by pushing down and tightening the fixings. This is a simple, low cost solution but has the drawback of a tendency to warp or twist, with a rough appearance and reclading work takes time to fix.
Aluminium Grip-Rail for ground, side & end rails – an extruded Aluminium box section rail with an integral 'T' slot for sliding in bolt head fixings. The polythene is held by a two piece PVC in-fill strip to secure the cladding material . The Aluminium rails offer a strong rigid fixing without cutting the polythene and makes easy work of cladding with control over the finish. The plastic in-fills can be replaced or removed for recladding work and are available in two versions to cover the range of thickness in materials.
Aluminium rails are available in a single channel section for base rails, a double channel section for side ventilation mid height rails and gable end lintels. A single channel clipping rail is also available to clad around door openings.
Anti-Hot Spot Tape
Anti-Hot Spot Tape is an over-hoop foam insulation tape with a slippery surface coating. AHST is applied to all steel frame components that are in contact with the polythene cladding. This is essential to reduce heat transfer & abrasion thus dramatically increasing the life of the polythene.
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Cladding Material
Polybuild only supply British Visqueen polythene to provide our customers with a quality, long life and high performance product in line with our own structures. All supplied polythene is guaranteed against any manufacturing defects for 5 years and we do recommend to budget for replacement every 5 years although sheets will usually last up to 7 years.
The following polythene options are available 'cut to size' through Polybuild.
Clear transparent 720 gauge. This allows maximum unfiltered light through and is the standard budget option.
White 720 gauge with a light transmission of 65% which is ideal for growing plants which require shade and a cooler environment such as to keep nursery stock ticking - very suitable for retail areas and animal housing.
Clear Politherm AF 720 gauge. Enhanced energy saving and anti-condensation droplet formation. Politherm will provide 2 - 3 degrees C higher temperature versus clear. Politherm also provides improved light levels particularly in spring and autumn by 10 - 15% and is suitable for bedding plants, flowers and strawberries.
Luminance THB AF 800 gauge.Providing diffused light to increase growth and yield, Infrared solar radiation is screened out to keep the environment cooler without a similar reduction in photosynthetic radiation. An anti condensation additive is applied to the interior surface of the film and the cloudy finish to this material helps reduce scorching on hot summer days. With a high light diffusion this film is recommended for a variety of crops especially nursery stock and ornamental plants.
Polybuild supplies a range of Monofilament shade/windbreak netting in rolls or as sewn sheets. Please contact our sales department for further details 01903 892333
Structure Strength and Wind Speed Design
Fitting Crop Supports can improve the rigidity of your Polyhouse, although not essential Crop Supports will improve the rigidity and wind speed handling by approximately 10%. If you are on a very exposed site the wind speed handling can be further improved by reducing the hoop spacings - available as an option for each structure. On large multispan structures longitudinal tie bars can be fitted to further tension the unit as a whole.
Snow loading can be increased by up to 50% with the use of crop supports and is essential for net clad structures.
Door Options
Ruche Up Flaps -Suitable for the 'popular' range Ruche up flaps are the simplest & cheapest end enclosures and comprise of a polythene blind reinforced with timber lathes which slide in a simple guide.
Door Panels, Timber framed doors are made from truss grade tanalised timber, 90mm x 40mm cross section. They are factory assembled via mortice & tenon joints and clad with "Correx" rigid plastic sheeting.
Steel framed doors are welded from 32mm x 32mm cross section steel and then hot dip galvanised. The steel frames are clad in PVC Biolex rigid plastic.
Hinged Door kits are complete with galvanised "T" hinges, handles, tower bolts, drop bolts, auto latches and door stops.
Sliding Door kits are complete with aluminium extrusion combined door track and drip proof heading, quadruple sealed bearing carriages, steel bottom track guide. |