Commercial Single Span Aluminium Polytunnel

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Full Aluminium & MAGNAtube® coated Steel construction, for superior strength and longevity. W-Wire fixing system for fast construction and a superior finish.

  • Robust 2.5mm Wall MAGNAtube® coated Steel foundations
  • Full metal construction
  • Cover tensioning system to ensure a drum tight finish
  • Superior brackets & Fittings
  • Wind & Snow loading calculations to ensure suitability for even the most exposed locations
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If you need help with your purchase or have any questions call us on 01282 873120

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This is our highest standard commercial single span which offers superior quality and lifespan and is free of any timber elements.

Over time it works out better in terms of strength, value and longevity which is why it offers the best return on investment. This has been our best rated single-span polytunnel range and continues to be a firm favourite with our experienced commercial growers.

Our aluminium profiles have been extensively tested, each of which promises strength along with the ease of the W-wire fixing method which results in a clean and professional finish on the structure.

The foundation tubes are thicker at 2.5mm with a cover tensioning system that allows you to tension the cover after it’s been fitted, ensuring a drum-skin tight finish.

Our in-house engineers have calculated the wind and snow loads for our structures to ensure that every polytunnel that leaves us can withstand the weather at your location.

Northern polytunnels are renowned for their strength which is why you can expect to see them in the most hostile environments, from the Shetlands to The Falklands.


Unique Polythene tensioning system – Allows the polythene to be tensioned or loosened as needed throughout the year

Lumisol Polythene – A British made, 7 layered polythene that has been specifically engineered for the British weather

Our 4-piece hoop is made up of a 2-piece arch connected to a straight leg. Making them stronger and able to withstand a heavier load

Aluminium Base Rails, Aluminium Door Frame & Aluminium Doors with brush seal as standard – No specialist tools required, no digging, no sawing and definitely no rot.

U.K. Manufactured from the brackets to the polythene.

Armourguard Coated Steel Framework – Galvanised to last a lifetime

Foundation Tubes – 2.5mm thick (others use 1.5mm)

Single Span Polytunnel
MAGNAtube® 50-60mm Pre-Galvanised Steel Hoops
Cover Tensioning System for Increased Cover Life
Commercial Grade Sliding Doors
Aluminium Box-Section End Frames
Roof, Side & End Vents with Full Automation Available
Robust UK Manufactured Bracketry
Clear, Diffused or Twin Skin Covers Available


Northern Polytunnel Hoop Design

Our 4-piece hoop is made up of a 2-piece arch connected to a straight leg. The leg connection is located on a vertical plane meaning the hoops can withstand a heavier load. Manufacturing a hoop in this way also makes the hoop more customisable by giving the customer the ability to increase the height of the straight leg without compromising the stability of the single span.

four piece hoops

Other manufacturers of Polytunnels often have their connections on the curve of the hoop which compromises strength and allows the hoop to ‘snake’. To combat this, extra bracing brackets are used resulting in increased materials, labour and cost.

Wiggle Wire Aluminium Fixing Profiles

Aluminium is free from defects that wood has (knots, splits and bows) and will last a lifetime. All our aluminium profiles incorporate our unique ‘W-Wire’ polythene securing system. By simply weaving the ‘W-Wire’ into the open channel of the aluminium rails & frames the polythene is securely trapped in to place. ‘W-Wire’ is the easiest and quickest system on the market and doesn’t require any specialist tools.

Wiggle Wire fixing

Aluminium Side Rail And Door Frames

After years of research and development we have designed a profile that has the strength of a box profile with all the features that you expect from a modern fixing system.

Base Rail Fixing

  • T slot rear fixing for bolts
  • Wiggle wire fixing of up to 3 different materials
  • Keder slots for simple curtain replacement
  • Strong purpose designed door frame fittings

Aluminium Base Rail

This is a smaller section size but still retains the strength of a box profile, with the simple wiggle fixing system

Base Rail Fixing

  • T slot rear fixing for bolts
  • Wiggle wire fixing of up to 3 different materials

Superior Brackets And Fittings

The strength of our brackets and fittings have been proven for over 40 years and have been specially designed and manufactured in-house. Bespoke fittings are designed to simplify the construction process, thereby reducing the construction cost.

Superior Brackets

ArmourGuard® Steel

ArmourGuard® is NP Structure’s developed high-endurance galvanising treatment, giving extraordinary levels of corrosion resistance. ArmourGuard® offers up to 20 times the corrosion resistance of traditional zinc galvanising due to the combination of zinc, aluminium and magnesium.

ArmourGuard corrosion resistance

Configurable Options

Different crops and growing systems require different solutions, which is why we offer a range of options to suit your individual requirements and budget. Options include; doors & louvres – foundations – brace and crop bars – choice of polythene covers – ventilation systems and irrigation.

configurable options

BPI Polythene

Visqueen’s British made polythene allows UVB to enter the greenhouse unlike normal glasshouse films and glass. This has many benefits including enhancing the fragrance, taste, colour of crops with the added advantage of earlier harvesting and longer post-harvest shelf life. It also has a unique condensation reduction additive to further reduce light-loss. Our polythene is guaranteed for 7 years*


*incremental guarantee from invoice date


Our ground tubes (Foundation Tubes) are 1m long, they are ArmourGuard galvanised treated with a 2.5mm wall thickness.
The image shows a ground tube concreted in with a retaining bar to hold it securely

Ground Tubes

Cover Tensioning System

All of our foundation options incorporate our unique polythene cover tensioning system. The collar tensioning system enables quick and easy tensioning of the polytunnel cover.

The hoops sleeve over the foundation tubes allowing each hoop to be raised individually and locked into position after the polythene sheet has been attached. This stretches the polythene cover to create a drum-tight like cover finish. Unlike some competitors, our system allows easy tightening and slackening throughout the lifespan of the polytunnel

polythene tensioning



MAGNAtube framework and aluminium upgrades available to maximise product lifespan


Both self-build and turnkey solutions available to suit your time frame


Manufactured at our Lancashire facility and delivered by one of our fleet of vehicles


Easy to add side and/or roof ventilation as necessary


Greenhouse Standard EN13031 ensures durability against wind and snow loadings


An easy-to-use tensioning system ensures a drum tight cover, extending the polythene’s lifespan





Polythene film: Diffused or Clear?

Light Transmission

  • Light transmission is the quantity of light going through the polythene, measured by %.
  • For temperate climates, a rate of higher than 85% is the target.

Thermal Efficiency

  • Where the heat in the tunnel is retained during the night.
  • This is measured by thermal retention + thermal transmission = 100 and is expressed as %.
  • The higher the thermal efficiency, the better the polythene retains heat.
  • The higher the thermal transmission the more energy is lost.


  • The anti-drip coating reduces condensation droplets and produces more of a film of water.

Benefits of Anti-Drip

  • Reduces the risk of droplets then dripping which can cause fungal diseases.
  • Improves the quality of light for photosynthesis, Droplets of water cause light refraction reducing the quality of light.

Note: requires adequate management of the internal micro-climate through ventilation.

Lumisol Clear – Clear Polythene

Lumisol Clear Polythene

The clear polythene improves the passage of light into the tunnel to promote photosynthesis.

Clear polythene is measured by haze. The lower the % the clearer the polythene appears and the more light is allowed to be transmitted.

  • Our clear polythene has 30-35% haze.
  • Our clear polythene has 88-92% light transmission.
  • Our clear polythene has 80-85% thermic effect.

Benefits of clear polythene:

  • Improves the quantity of light to encourage photosynthesis.
  • Encourages early crop yields and crop strength.
  • Increases daytime temperatures.
  • 5-year incremental guarantee, although a 12-14 year lifespan is not uncommon.

Lumisol Diffused – Diffused Polythene

Lumisol Diffused Polythene

The diffusion effect ensures better light distribution inside the polytunnel, Diffused Polythene is measured by haze.

The higher the % the cloudier the film is, the more light it defuses.

  • Our diffused polythene has 90-93% haze.
  • Our diffused polythene has 87-91% light transmission.
  • Our diffused polythene has 80-85% thermic effect.

Benefits of diffused polythene:

  • Reduces the stressful effect of direct sunlight on the plants.
  • Reduces the risk of leaf burn and crop deformation.
  • Encourages a more uniform ripening and colouring of the fruit as less shadowing is cast. Note: designed for use in very luminescent areas of the UK.
  • 5-year incremental guarantee, although a 12-14 year lifespan is not uncommon.

Side Vents

Over a certain length, commercial tunnels can struggle with stagnant air in the middle of the structure that airflow from open doors cannot circulate.

The best recourse for this is to opt for side ventilation. Whether manual winch, gearbox or motor-driven, it gives the grower control over the environment in the polytunnel.

Opening the side vents allows air to flow throughout the tunnel reducing hot spots in summer. Closing them during cooler months reduces heat loss and encourages the grower to bring on plants earlier in the year.

Side vents are designed work in conjunction with open doors and/or roof ventilation, allowing full circulation through the tunnel.

Commercial Timber Range

  • Timber Base Rails
  • Timber Side Rails
  • Timber Battens
  • Full Depth net with PVC skirt
  • Draft Panels
  • Manual Gearbox
  • Aluminium Curtain Tube with Keder Slot
  • Wind-Up PVC Curtain with double Keder

Side Vent Options

This is our professional range side vent with a manual gearbox operating the internal roll-up PVC screen. This system is available for polytunnels with timber side rails.

The PVC screen and exterior netting are battened on to the side and base rails using wooden laths. The netting comes complete with a solid draft-proof skirt, draft panels are also fitted to the mesh where the curtain ends to minimise the cold air entering the tunnel. The PVC Screen fits inside the aluminium drive tube using a Keder bead and is raised or lowered with a manual gearbox. (An automation option is available)


We only offer sliding doors on our commercial tunnels. Over the years we have learned that doors on polytunnels work better and last longer if they slide rather than swing.

We offer 2 models; a low-cost timber framed, clad in polythene and our new heavy duty aluminium frame, clad with PVC. Both versions come with our aluminium profile sliding track and 4-wheel roller carriages.

Low-cost Timber Doors

  • 3” x 2” timber with fixing battons
  • Polythene cover
  • Nail plate joints
  • NP door furniture Door shoes fixing to the posts, drop bolt at the back of the door, door catch, small channel to hold the together when shut.

Timber Commercial Doors

Heavy Duty Aluminium

  • NP designed aluminium door profile with wiggle wire fixing system
  • Clear PVC top panel
  • PVC grey lower panel
  • Steel, bolt on triangle corner plates
  • PVC finishing strip to cover the perimeter wiggle wire
  • Brush strip seal at the rear of the door (optional)
  • NP Designed door furniture, Door shoes to fix to the door posts, drop bolt at the rear of the door, full length channel section to form a seal between the doors, door catch.

Aluminium Commercial Doors

End Louvre Vents

Louvres are easily fitted to the ends of our structures. They can be used in conjunction with doors and the configuration can vary, depending on the size of your structure.

Louvre measurement: 0.79m x 2.12m.
Actual ‘opening’ size: 0.8m x 2.15m.

Louvre vents

Ventilation Louvres – Pull Cord (Gable end instead of a door)
These feature our unique 3 positional hinge which locks the louvre in place. This allows the louvre to be set in the fully open position, (90°) 1/2 open (45°) or closed. These can either be single row or a double row (as above) for extra ventilation.

configurable options

Ventilation Louvres – Rack and Pinion (Above the door)
These louvres feature a rack and pinion system for opening, controlled by a gearbox with winding handle. The rack and pinion louvres are fully adjustable, not just limited to the three positions like the pull cord louvres.

Crop Bars

It may seem like an obvious statement, but the more steel in the structure, the stronger it is. How much steel you need can depend heavily on the prevailing weather in your area. You can use the maps and tables included in this brochure (page 6) to check your average wind speed and snow load. This will help you to determine which kind of crop bar hangers you should choose; the “Inverted V” for lighter weather loading, or the sturdier “W-Hangers” for heavier weather loading, load bearing apparatus and crop support.

Formed from 50mm and 32mm diameter, Armour-guard coated steel tubing, our crop bars and hangers are just as strong and durable as the hoops they service. Not only do they pin the hoops together, they prevent lateral movement and joint loosening. When fitted with “W-Hangers”, they’re strong enough to carry direct loading. This is often seen in retail locations where large numbers of hanging baskets or planters are to be displayed. Crop bars also form the backbone of vital irrigation and air circulation systems as they are able to carry the additional load of water pipes, heaters and fans.

Our crop bars are just another reason why Northern Polytunnels produce the most robust tunnels on the market, specifically designed to stand up to the worst that the British weather can throw at them.


V Hangers – Sufficient throughout most of the UK

V Hangers for polytunnels

W Hangers – Used in more extreme locations on wider tunnels

W Hangers for polytunnels

Roof Ventilation & Controllers

These roof air extraction fans have revolutionised the way that polytunnels can be ventilated. These fans extract heat from the roof space of the greenhouse at its highest point. Which, in turn, draws cooler, fresher air in from the doors or side vents creating air movement in the structure. The 240v fans can be connected to either a simple on off switch, one of our fan controllers or a climate computer.

Roof Fan
The number of fans required depends upon the volume of warm air you want to expel and how quickly you want to expel it. As a general guide we would recommend a maximum of one fan for every 350m³ of air space – this would allow up to 13 air changes per hour.

Typically, one fan would be required for every 35ft to 80ft of polytunnel, depending on the width, height, and existing ventilation systems. For a 30ft (9.14m) wide polytunnel this would be approx. 1 fan for every 36ft (11m) length of polytunnel.

Therefore, a 30ft wide x 110ft long polytunnel would require a maximum of 3 fans. Even if only a single fan was installed you would still feel a significant difference as you would still achieve 4-5 complete air changes per hour.

Fan Controller

This precise, adaptable and dependable temperature controller is the ideal partner to any of the air circulation fans offered in our brochure, allowing for maximum economy and temperature control.

This robust unit can also be configured to work with heaters in winter. It’s a fantastic way of keeping simple, but accurate control over your growing environment.

  • Function for ventilation in summer
  • 1 Single temperature dial control
  • From 0° to 30° control
  • Temperature sensor on a 20m cable
  • Fan appliances output load 1kw inductive
  • Can run up to five roof fans
  • Splash proof IPX4

Circulation Fans

Optimal ventilation is vital as it plays a significant role in the cultivation of crops. Effective air circulation not only supports but drives crop growth and gives the grower complete control over the climate inside the tunnel.

Mould and fungal diseases thrive on poor ventilation, which is why proper air flow is so important.

It’s not all about the heat. On a humid and sunny day, when the temperature inside the greenhouse rises excessively, it’s important to open the vents to avoid overheating and to spread that cooler air evenly throughout the tunnel. This can be achieved using circulation fans throughout the structure.Fans

Overhead Irrigation Systems

NP overhead irrigation kits utilise the best components we can source including VDL valves and pipework, Netafim down tubes, anti-drip valves and nozzles giving high spray uniformity with minimal wasted water.

Our kit includes 30cm weighted down tubes, anti-drip valves and a nozzles/sprinkler specific to each width of greenhouse, twin 32 mm PVC spray-lines with PVC ball valves on each line, these are connected to a 50mm PVC header manifold with a drop pipe and connection for a Geka snap coupling.

All straining wires, tensioners and header brackets are included in the kit.

Sprinkler Performance

Each sprinkler is connected to a weighted 30cm down tube this allows the sprinkler to work in a true plumb position for optimum performance.

These are connected to a pressure release anti drain valve, these prevent the water within the sprayline dribbling out after a watering period has ended, saving water and leaving the line ready and primed for the next use.


Benching & Staging


Our robust cost-effective benching system is modular meaning that its easily dismantled and reassembled to expand or reduce in size.
The benching comes as a flat pack which is easy to re-site or store when not in use.

The construction is based on our ArmourGuard 25mm diameter tube which has a magnesium zinc coating for years of rust-free life. Our specially designed corner and side fitting gives the bench its modular capability and strength. It is supplied with four corner bracing bars to give extra stability.

The bench top is a hot dipped galvanised mesh with a 3mm wire diameter and hole size of 25mm x 75mm.

Available in 1mtr wide and in multiples of 1.2m lengthways, allowing you to create a continuous bench to suit the length of your polytunnel or plant display area.



Our staging kits are a low cost solution where a full length bench is required for your polytunnel.

We ONLY provide the steel frame, leaving you to provide your own table-top. Some customers use heavy-duty, galvanised weldmesh, whereas others choose timber slats. Whatever your choice, our staging kits provide the ideal framework on which to grow your potted plants. Supplied with fasteners for fixing timber slats.

Our staging can be installed in new and existing polytunnels.


Danish Trolley Track Mat

The Danish Trolley track and ramp is easy to lay and move, and can be used as either a permenant or temporary track. The interlocking sections (end to end) ensure smooth and quiet trolley movement and are supplied in 1.2m x 0.54m interlocking lengths. The track is heavy-duty,long-lasting and made from recycled plastics, with a built-in anti-slip surface along the centre.

Quantity = length of the tunnel ordered

Danish trolley track matting

Ground Cover

ground cover

With less than 5% light transmission, ground cover is an effective weed control fabric. Manufactured from black polypropylene (100gm/m2) with 25cm x 25cm green grid lines for accurate plant spacing.

Optimum water permeability (15ltr/m2/second). Ideal for above-ground or below-ground applications.



We strive to give our customers the best product. For this reason, we undertook the huge task of analysing the strength of our polytunnels. This is done creating a computer-generated model of the structure and applying loads from the relevant standards shown in the table opposite.

These loads are applied to the model of the greenhouse using our structural analysis software. The software helps us to locate potential weak spots so that we can optimise our design.


The table below shows the wind and snow load numbers, the higher the number the stronger the greenhouse required.

Using the maps, pinpoint where your structure is to be sited; note the colour and zone. Each zone relates to snow loading and wind speed throughout the country. Check the polytunnel wind and snow load performance table to make sure the polytunnel will perform in the area you have pinpointed. If you need further help with this, please don’t hesitate to get in touch with our sales team.