In stock

Tunnel houses / Polytunnels 3.7m and 4.9m wide.

You can cover a much bigger area than a glasshouse of similar cost, "more bang for your buck"

In a recent Kiwi Gardener article (quarterly special, Under-cover Gardening) a writer Dianna Noonan on page 9 writing about polytunnels said "you won't get more than a couple of seasons from them before they begin to deteriorate". It is a shame some writers don't do even a small amount of research before writing articles. It may be true of some cheap tunnels, but in our case that statement is completely wrong. We use commercial grade EVA polythene, the same product commercial NZ growers are using. Even common sense tells us that commercial growers, sometimes with hectares of valuable plants under a plastic cover, are not changing their covers every few years? It would not be economic. I would be surprised if the cover we supply did not last at least 10 seasons if looked after. I had a cover on tunnel house that lasted 15 seasons and that is with old technology plastic.

Expensive glass does obviously last longer, except perhaps in a severe hailstorm. And what about the glass to frame seals? They are often some plastic or rubber compound sandwiched between the glass and the frame in full sun. I wonder how long they last before going brittle? Nothing lasts forever.

Please note we can also use our frames to make a very strong shadehouse, something to consider if you want to protect young plants from intense summer sun. You will find plants grow very well in some shade, especially a small seedling tree that would normally start on the forest floor protected by its larger parents.

COVID-19 has changed the world, probably forever. It won't be the last time we see it, and should it come back more contagious and deadly, leaving home to get food might be very risky. Time to get more resilient and less reliant on supermarkets for your fresh herbs, fruit and vegetables. If you want to have on hand fresh food at any time of the year, crop protection is essential. Whether it be from birds, pests, weeds, weather or diseases, it is an important next step for producing healthy quality crops with minimal wastage and chemical use.

If you are after something smaller and cheaper, 2.4 m wide? Check our our NZ made domestic tunnels here Domestic tunnel houses

Please note. We do not sell individual components to people who want to build their own polytunnel. We keep our components for our own polytunnel customers in case they need after sales service.

Strength and durability is the cornerstone of our business and we don't believe in cheap, flimsy materials. That's why we were pleased to find a range of polytunnels that are designed and manufactured in the UK by Northern Polytunnels, one of the leading Polytunnel manufacturers in the UK. They only use the highest quality materials, such as high-performing Z35 grade steel with special protection against corrosion. Read on ......

We have always preferred aluminium for construction because it does not rust, however it is not as strong as steel. With ArmourGuard®, a newly developed high-endurance protection treatment, steel tube becomes the material of choice. By combining extraordinary levels of corrosion resistance with the durability of high strength steel we have an ideal structural material that easily outperforms aluminium as a main structural component. ArmourGuard® offers up to 20 times the corrosion resistance of pre-galvanised steel tube thanks to its revolutionary combined zinc, aluminium and magnesium coating.

ArmourGuard® is designed not just to survive in the most hostile environments, it also offers extreme longevity. In exhaustive tests carried out by Rotech Laboratories, one of the UK's leading test houses www.rotechlabs.uk.co.html ArmourGuard® endured the equivalent of 100 years' exposure to the harshest elements without undue deterioration. Real life can be a bit different, but we are confident to give ArmourGuard® coated components a 20 year guarantee against corrosion.

Aluminium bottom rails and door frames means there is no timber to rot and warp or to leach treatment chemicals into the ground.

Environmentally Friendly
ArmourGuard® even protects the environment by reducing the amount of zinc which is used in the manufacturing process compared to the fully galvanised steel tube. By extending the product life we are also reducing the overall long-term consumption of steel and the related energy inputs.

Three month salt water spray test comparison

Top: Plain Steel, Middle: Hot dip galvanising, Bottom: Bottom: ArmourGuard

Please Note. Our 20 year guarantee against corrosion applies to ArmourGuard tubular steel components only (arches, stabilisers, bracings & ridge tubes). Even though all the brackets and fittings are also fully electroplated, they are not protected with our ArmourGuard® coating and as such do not carry the same guarantee. However, the steel used to manufacture our fittings is 2-3 times thicker than the wall thickness of the steel tube. Our polythene covers and anti-hotspot tape has up to a 5 year pro-rata guarantee against UV degradation, but since it is the same cover material that is used by the commercial horticulture industry in New Zealand, we expect it to last longer than this if looked after.

Question: So why use plastic if it fails in time, why not glass that lasts longer.

Answer: It is about cashflow. If you are going semi-commercial, or going to grow for a Farmer's Market, you can get a lot of polytunnel for a lot less money than a glass greenhouse of the equivalent size. This means you may be able to avoid a loan (going into debt) and all the interest asscociated with it. If your venture is successful the profits will give you the ability to replace the cover at a later date out of your cashflow. I have a cover on one of our smaller domestic tunnel houses that is still the original cover after 15 years!

All the steel tube is UK made Z35 construction grade steel that is corrosion protected both inside and out. The tube is 32mm in diameter with a 1.5mm wall thickness.

Benefits of Purchasing one of our Polytunnels

"More bang for your buck" Cover a large area a lot cheaper than if you used polycarbonate or glass

Screw Anchors - No digging, no mess and very quick. Strong grip in the ground.

Strong 32mm diameter steel hoops - ArmourGuard® treated, long lasting for all weather conditions

Aluminium Sliding Doors - Easy to assemble and problem free

Aluminium Door Frames - Pre-cut - no carpentry required. Concreted in the ground for extra strength

Aluminium Base Rails - No need to trench-in the cover. No rot, no leaching, no warping

'Wiggle Wire' Polythene Fixing System - Quick, simple & secure and easlity undone if required.

Anti-hotspot tape on the frames that come into contact with the cover - it makes the cover last much longer

Cover is drum tight - makes the cover last a lot longer

200mu cover - Cover material is widely used in NZ on commercial tunnels, one of the best available.

The cover is a one piece rectangular sheet, not welded - No seams to break open and you can use any supplier in the future for a replacement cover if you wish. You are not tied to any particular manufacturer. The frame can also be covered with shade cloth to make a shade house.

Screw Anchors By far the best and most popular method. Suitable for most soil types, especially clay soils. Avoid only on ground with a high stone/rubble content, peat soils, or loose soil which has been recently disturbed or deeply cultivated. In this case it is advised to dig a hole with some undercut and concrete in the screw anchor.
Each screw anchor only takes 1-2 minutes to screw into the ground. Compare this to the time it takes to dig each hole when using either the concreting method or ground anchor plates, and without any of the mess or exertion. In recent tests, the strengths of different polytunnel foundation options were measured. The tests showed that the screw anchors out-performed all other methods in most types of soil.

Screw anchors also incorporate a unique polytunnel cover tensioning system where the hoops are raised (and locked into place) after the cover is attached to achieve a drum-skin tight finish. The tighter the cover, the longer it will last!

Screw anchors are screwed approximately 500mm into the ground (T bar supplied)

Stronger Two Piece Steel Hoops For All Weather Conditions
Hoops that are made from three or four pieces are easier to make and more convenient to deliver, however they are not as strong as a two piece hoop and often require extra bracing bars to support them. That is why we only have two-piece hoops, and one of the reasons why so many of these polytunnels are sold to customers in the Scottish Highlands and Scottish Islands. All the steel tube is protected with ArmourGuard® coating, 32mm diameter with 1.5mm wall thickness. Z35 grade steel.

Doors...Easy to Assemble and problem Free

Aluminium Sliding Doors. Made from easy-to-asemble aluminium sections incorporating our unique "W-WIRE" polythene fixing system. Supplied with enough materials to fully clad it with polythene, or to clad the top half with netting for extra ventilation.

An optional extra aluminium door can be installed at the other end to give a door both ends.

Aluminium Base Rails, Aluminium Door Frames all pre-cut.
Due to the natural variances which occur in timber and its much shorter lifespan we use aluminium for the base rails. Some customers are concerned about CCA treated timber (Copper, Chromium, Arsenic) leaching from timber into the soil and possibly being taken up by their crop. There is no CCA leaching with Aluminium. Aluminium is also straight and does not warp like timber can, a big advantage in a long polytunnel. Macrocarpa will rot in contact with the ground so not a viable option.

Note the strong aluminium door frames (profile shown below) are put into the ground (both ends) resulting in even more strength. I prefer to concrete them in for extra stability.

"Wiggle Wire" Polythene Fixing System...Quick Simple & Secure
The aluminium base rails, doors and door frames all incorporate our unique "W-Wire" polythene securing system. Simply weave the "W-Wire" into the open channel of the aluminium rails & frames securely trapping the polythene in place. Don't worry if you have to redo a section, it's easily unclipped and can be wiggled back into place in a jiffy, ensuring a tight neat finish every time. This is especially useful when pleating the polythene around the door frames. We believe the "W-Wire" method is the easiest and quickest system on the market. If you are in a very exposed postition, then for a very small cost, extra "W-Wire" can be purchased to double up the fastening of the polythene.

Watch the videos below to get an honest review and also a detailed video the assembly. Note: Tony O'Neil was not given a Polytunnel for the review. I would aslo urge you to look at his other practical videos on gardening for some great practical gardening advice.

VERY IMPORTANT The poytunnel assembly videos shown here have 6ft (1.829m) hoop spacings. Our polytunnels are the 5ft (1.524m) version, so where Tony says place the ground augers 6ft apart, on our polytunnels they are 5ft apart. We opted for the slightly more expensive 5ft option as it supports the cover at closer intervals and is of course stronger in extreme weather. Worth the extra we think.

Follow the link to view some helpful assembly videos and other info (click videos and gallery midway down their page) Please note we do not stock all options shown here and we don't use any timber in our polytunnels. Whilst aluminium is more expensive, it is also far more stable and there are no importing issues. If Biosecurity NZ find a daddy long legs spider inside the container holding a union jack we have all sorts of issues. Northern polytunnels Easy Build polytunnels

A printed assembly manual in colour is supplied with each kit and you can also download it. Follow the link below.

Click here to download a PDF of the assembly instructions (10.1Mb)

Wind ratings

There is no doubt our weather is getting more extreme, so customers are often asking about a wind rating. In my view wind ratings are just hype and a marketing ploy. The devil is in the detail and they are not normally stated. How do you wind rate a polytunnel or greenhouse with so many variables? Here are just few variables.

1/ One of the biggest dangers is a polytunnel lifting off the ground. Our augers are wound 500mm into the ground so are very secure. However, obviously their holding power is greatly affected by the soil type. In clay you would probably need a hydraulic lifter to pull them out, in sand who knows. Is the soil saturated with water? Again this affects the holding power.

2/ Is the wind rating for any direction? Obviously side-on has more wind pressure on the structure than end on.

3/ What about length? Side on, the longer the polytunnel, the more wind pressure.

4/ Is the figure theoretical, or is every size tested in a wind tunnel from all angles? I doubt it.

And then the irony - A high wind rating, but the guarantee excludes storms. Isn't that when you get high winds?

I am a practical person, so the construction of the polytunnel has more meaning than any theoretical wind rating.

How about ….
1. Sold into the Outer Hebrides and the Falkland Islands, not much shelter there.
2. Steel augers approx. 500mm wound into the ground
3. 32mm diameter Z35 grade British made steel tubing.
4. Heavy duty British made steel fittings
5. Big solid aluminium 75mm box section door frame extrusions each end
6. Grade 8.8 high tensile bolts, often called "structural grade" with nylock nuts so they don't vibrate loose in high winds.
7. Optional cross brace bars and ridge bars for added strength.

We prefer real life. What is our own experience after for 4 years selling these polytunnels in New Zealand? No damage reported from storms or Cyclone Gabrielle, we feel that says it all.

The Easy-Build kit, Basic kit, what is included.
Our basic Easy-Build polytunnel kit includes all our unique features mentioned above, but also includes our most popular options: Single sliding door at the front, screw anchor foundation tubes and Polygro EVA 200mu commercial grade greenhouse film that we source from a New Zealand supplier to get the most UV resistant material.

The series of pictures below show a 1.8m tall person standing inside one of our polytunnels. Grow tall plants right to the walls.

Being UK made the sizes are in feet so we have converted to the approximate equivalents in metres. Steel hoop spacings are at 1.52m (5ft) for extra strength. Northern Polytunnels have an option of 6ft spacing, but with only a small in price difference we felt the strongest available for a little more was a better option.

Further options can be added at extra cost such as double doors (wider models) cross bars, extra ridge tubes, extra rear door, roll up side ventilation and staging. Prices in the table below are for the basic Easy-Build kit.

Basic kit prices (including a single door. You can change to a double door for an extra fee) including GST, excluding freight

Please note the GST inclusive prices in the table are ballpark figures. Please email us with your requirements and we will give you an accurate quote. We can do virtually any length, provided it is in 5ft (approx 1.52m) increments. Contact us

Freight is additional and we will obtain a quote on this once we know what is wanted.You can also pick up from our base in Tuakau for a minmal fee (we sometimes have the covers freighted to you from Auckland seperately and don't hold them in stock). Please contact us for a quote. Contact us

Door Frame and Door Options

Single Aluminium Sliding Door with optional vent screen

Our Easy-Build polytunnel comes with aluminium doors and door frames as standard with each piece of aluminium cut to size, eliminating the need to cut down or trim any excess material. Each component easily fastens together using steel brackets, removing the chances of making mistakes whilst also removing the requirement for carpentry skills (which would be required to assemble timber doors). All doors are supplied with all the necessary hardware, including door guides, handles, drop bolts etc.

Aluminium Sliding Doors Made from easy-to-assemble aluminium sections incorporating our unique "W-Wire" polythene fixing system. Supplied with enough materials to fully clad it with polythene, or to clad the top half (optional) with netting for extra ventilation..

Several door options are available Our single door frames have a 0.8m opening. The double door frames have a 1.7m opening.

The height of the door lintel is approximately 2m.

Double Aluminium Sliding Doors with optional vent screen

Extra single door including frame for the door to fit in. approx $1,220

Double door including double frame for the door to fit in. approx $1,797

Double doors can be fitted both ends, for the additonal door. Please note the picture shows the optional vent system.

Ventilation Options

PVC Ventilation Panels, no access.

Ventilation partially open

Ventilation open

Ventilation closed

Fabricated from a translucent PVC fabric mesh insert. It comes with a removable translucent PVC fabric panel which simply attaches over the mesh (to seal the vent) with its Velcro edging.

The panel can be fully opened, fully closed or partially opened. Gives ventilation without allowing unwanted pests to enter your polytunnel. Quick and easy to fit. Only available with single door frames and only one per structure as this option isn't used for access.

$226.88 plus freight if ordered by itself.

No extra freight if orderd with a polytunnel.

Side vent half open

Side Ventilation (optional extra)
Although doors offer ventilation on shorter polytunnels throughout most of the growing season, additional ventilation can be necesary on longer tunnels, especially if you are growing through a hot summer. This simple to operate, low cost ventilation system offers a practical solution during hot summer months. Simply wind up the polythene side when required and wind down when you want to retain heat. The screened openings keep most bugs at bay. These can be fitted to one or both sides of your tunnel. The kit includes an aluminium side rail, external polythene wind-up screen and netting (to cover the ventilation holes). The holes are cut into the main cover once the side rail has been attached. This kit can be fitted to one of our tunnels at a later date if required. Please note the vent cloth is white not green as shown in the picture.

Approx $167.00 per bay per side plus freight

Horizontal brace bars, 12ft model. Staging to the left is not included.

Brace Bars (Widthways Crop bars) (optional extra)
Although often used to hold hanging baskets, or to support lateral poles on which to tie up your tomatoes, beans peas etc, they are often added to a polytunnel to give it extra strength. Even though we boast our tunnel houses are very strong, they give peace of mind during severe windy storms and also when heavy snow is expected. They increase the strength by at least 20%, so well worth considering if you are in a high wind situation. Can be retrospectively fitted to an existing polytunnel. Brace bars when installed are approximately 1.85m above the ground.

Horizontal brace bars for 12ft wide tunnel approx $112 per bay plus freight

Horizontal brace bars for 16ft polytunnels come standard with crop hangers and are approx $186 per bay no extra freight

Additional Ridge Bars (Lengthways Crop Bars) (optional extra)
The basic polytunnel will always have a central ridge bar, but additoinal ridge bars can be added to either one or both sides of a polytunnel. They will increase the strength a little, but the main use of these is to provide crop support along the length of the polytunnel. They can be positioned and re-positioned to the most convenient place for the crop you are growing.

Ridge bars approx $186.00 per bay, no extra freight.

Staging (optional extra)
Our polytunnel staging kits are a low cost solution where a full length bench is required for your polytunnel. We ONLY provide the strong 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 provides the ideal framework on which to grow your potted plants. Supplied with fasteners for fixing timber slats. Can be installed in new and existing polytunnels.

Click here to download a PDF of the staging assembly instructions

Approximate pricing per side, ask for a quote