commercial polytunnels · constructing polytunnels for over 40 years. we now supply com-mercial...

Experts in Structures Since 1969.

npstructures.co.uk01282 873120

Compare us againstthe competition

polytunnels | raised beds | cloches | fruit cages

Our polytunnels help you grow

bigger, better & faster!

Commercial Polytunnels

Look out for the blue stars!

Turn to pages 11 & 12 for notes from ourstructural engineer

At NP Structures, we have our own in-house team of design and construction engineers.

John is our in-house Structural Engineer. He has gained Master & Bachelor of Engineering Degree in Architectural Engineering, awarded by The University of Leeds.

We’re all very proud of John and this achievements. and as he played a huge part of pulling together this comparison chart, we felt it only fitting he should have his own section.

Throughout this brochure you will see blue stars on some of the comparison sections, such as anchor plates, hoop pieces and storm bars. These stars indicate there is note about these sections within our Structural Engineer notes.

Notes from our Structural Engineer can be found on pages 11 & 12.

What is a Commercial Polytunnel?The basic functions of a hobby polytunnel and a commercial polytunnel are exactly the same. They are both used to grow crops, whether it is fruit or flowers. The basic design of a hobby polytunnel and commercial polytunnel are therefore the same. A steel frame structure covered with polytunnel polythene.

The difference however, is scale. Commercial structures are wider and higher. they can also be combined to make very large, multispan structures. Because of their size commercial structures must be capable of withstanding the larger wind and snow loads imposed on them.

Why have we made this comparison?We’ve made this comparison because we think it is important to highlight the differences between our structures and those of our competitors. We want to tell our customers the reasons we manufacture our polytunnels the way we do and show them the difference be-tween the framework, fittings and polythene that we supply and those our competitors supply.

This comparison looks at the Commercial Single Span polytunnels we supply and ‘Commercial’ Single Spans polytunnels offered by our competitors.

It’s all about being fit for purpose - the fixtures and fittings should be made of a commercial grade.

You’d never expect to find hobby polytunnel fittings on a commercial polytunnel...

...We wouldn’t, would you?

About usAt NP Structures, we have been designing, manufacturing and constructing polytunnels for over 40 years. We now supply com-mercial polytunnels to some of the most prestigious polytunnel growers in the UK and Europe.

Our in-house team is a collaboration of mechanical engineers, structural engineers, architects and construction experts.Our services include carrying out studies and preparing applica-tion drawings* for planning permission and building regulation approvals.

*Prior to an order this service will be subject to a standard charge which will be credited when an official order is received.

Notes from our Structural Engineer

3

Northern Polytunnels /NP Structures

First Tunnels

PremierPolytunnels

Framework

Foundation TubesHeavy duty galvanised foundation tubes with a

3.5mm wall thickness to give increasedprotection from corrosion.

Pre-galvansied steel tube with 1,5 mm wall

thickness.


thickness.

Framework Tensioning System Up to 250mm of tensioning is available byraising the hoops and locking into place.

None. None.

Anchor PlatesNot available. We would NEVER

recommend a commercial polytunnelto be built using anchor plates.

Used. Used.

Hoop Diameter 50.8 mm High Tensile* 50.8 mm 50.8 mm

Number of Hoop Pieces(also see Storm Bars / Storm Stays)

2 - For extra strength andease of construction

3 4

Number of Struts/Stabilizers per end. 5 5 5

Number of Pieces Struts/Stabilizers are supplied in.

1 2 1

Strut/Stabilizer Bar Diameter 50.8 mm High Tensile* 35 mm Unknown

Ridge Bar Diameter 50.8 mm High Tensile* 35 mm Unknown

Crop BarsMain Crop Bar Diameter 50.8 mm High Tensile* 35 mm Unknown

Number of Crop Bar Hangers 2 1 2

Crop Bar Hanger Diameter 32 mm High Tensile* 35 mm Unknown

Storm Brace Bars / Storm StaysThese are used to strengthen a weakened point due to multiple hoop pieces.

Not Needed.35 mm

(Optional Extra)Unknown Steel Size

(Optional Extra)

Timber & AluminiumEnd Timber Sizes 75 mm x 75 mm Tanalised 100 mm x 50 mm 100 mm x 50mm

Side Timber Sizes 100 mm x 50 mm Tanalised 75 mm x 47 mm 75 mm x 40 mm

Base Rail Aluminium Section Sizes 70 mm x 50 mm 37 mm x 14 mm NO ALUMINIUM OPTION

Side Rail Aluminium Section Sizes 70 mm x 50 mm 55 mm x 14 mm NO ALUMINIUM OPTION

FittingsType of Fittings Used Purpose made commercial fittings. U Bolts and/or Q Clips U Bolts / Q Clips / P Clips

Polytunnel Coverings

Polythene Manufacturer Bpi. Visqueen - UK designed & manufactured for the UK climate. www.bpivisqueenhort.com

Unknown, Imported Unknown, Imported

Anti Hot Spot Tape Manufacturer

We have used the same tape manufacturer for as long as the records date. It seems daily we

get offers for tape that costs much less. How-ever our tests have shown that the adhesive

simply isn’t up to the job - so much so, we have given up testing other suppliers and stick to

what we know!

Unknown Unknown

Misc.

Side Vent SystemGearbox operated 50 mm aluminium tube with an ‘alitrap’ fixing system to trap the polythene

curtain.

Gearbox operated steel tube with spring clips to

secure the polythene

Manually roll a steel tube with spring clips to secure

the polythene

Doors Commercial Aluminium Door 75 mm x 50 mm Timber 75 mm x 50 mm Timber

Irrigation Solid PVC commercial irrigation pipe25mm - Flexible LDPE

Pipe20mm - Flexible LDPE

Pipe

* Our steel work is High Tensile. Material certificates are available on request.

Compare us against the Competition

18 ft Single Span

Disclaimer.Every effort has been made to accurately represent the products of our competitors at the time of going to print. The findings above are based on information that is widely available on the internet. We suggest all customers research these finding before purchasing their own Commercial Polytunnel and not to base their decision on which supplier to select on the findings above.

5


First Tunnels

PremierPolytunnels

Framework




thickness.


thickness.


None. None.



Used. Used.




4 4



1 2 1

Strut/Stabilizer Bar Diameter 50.8 mm High Tensile* 35 mm Unknown


Crop BarsMain Crop Bar Diameter 50.8 mm High Tensile* 35 mm Unknown




Not Needed.35 mm


(Optional Extra)













what we know!

Unknown Unknown

Misc.


curtain.




the polythene




Pipe




24 ft Single Span

Disclaimer.Every effort has been made to accurately represent the products of our competitors at the time

of going to print. The findings above are based on information that is widely available on the internet. We suggest all customers research these finding before purchasing their own Commercial

Polytunnel and not to base their decision on which supplier to select on the findings above.

Disclaimer.Every effort has been made to accurately represent the products of our competitors at the time of going to print. The findings above are based on information that is widely available on the internet. We suggest all customers research these finding before purchasing their own Commercial Polytunnel and not to base their decision on which supplier to select on the findings above.

6


First Tunnels *

PremierPolytunnels

Framework




thickness.


thickness.


None. None.



Used. Used.

Hoop Diameter 50.8 mm High Tensile** 50.8 mm 50.8 mm



4 4



1 2 1

Strut/Stabilizer Bar Diameter 50.8 mm High Tensile** 35 mm Unknown

Ridge Bar Diameter 50.8 mm High Tensile** 35 mm Unknown

Crop BarsMain Crop Bar Diameter 50.8 mm High Tensile** 35 mm Unknown


Crop Bar Hanger Diameter 32 mm High Tensile** 35 mm Unknown


Not Needed.35 mm


(Optional Extra)













what we know!

Unknown Unknown

Misc.


curtain.




the polythene




Pipe

* We have used the First Tunnels 22ft in this comparison as they do not offer a 21ft. ** Our steel work is High Tensile. Material certificates are available on request.

21 ft Single Span

7


First Tunnels

PremierPolytunnels

Framework




thickness.


thickness.


None. None.



Used. Used.




4 4



1 2 1

Strut/Stabilizer Bar Diameter 50.8 mm High Tensile* 35 mm 50.8 mm


Crop BarsMain Crop Bar Diameter 50.8 mm High Tensile* 50.8 mm Unknown




Not Needed.35 mm


(Optional Extra)













what we know!

Unknown Unknown

Misc.


curtain.




the polythene




Pipe



30 ft Single Span

Disclaimer.Every effort has been made to accurately represent the products of our competitors at the time

of going to print. The findings above are based on information that is widely available on the internet. We suggest all customers research these finding before purchasing their own Commercial

Polytunnel and not to base their decision on which supplier to select on the findings above.

8Disclaimer.Every effort has been made to accurately represent the products of our competitors at the time of going to print. The findings above are based on information that is widely available on the internet. We suggest all customers research these finding before purchasing their own Commercial Polytunnel and not to base their decision on which supplier to select on the findings above.


First Tunnels

PremierPolytunnels

Framework




thickness.


thickness.


None. None.



Used. Used.




4 4



1 2 1

Strut/Stabilizer Bar Diameter 50.8 mm High Tensile* 35 mm 50.8 mm


Crop BarsMain Crop Bar Diameter 50.8 mm High Tensile* 50.8 mm Unknown




Not Needed.35 mm


(Optional Extra)













what we know!

Unknown Unknown

Misc.


curtain.




the polythene




Pipe



27 ft Single Span

9

Compare us against the CompetitionCompare us against the Competition

Notes from our Structural Engineer

What we do and why we do it.At NP Structures we don’t leave anything to chance. We only use the highest grade materials in all of our polytunnels and structures. On these pages, our Structural Engineer explains the materials we use, their grade and why we use them.

5. Ground TubesWith ground tubes being in the ground, they are likely to be in contact with water for extended periods of time. We use heavier gauge ground tubes which are hot dip galvanised to reduce the chance of corrosion. Our ground tubes, with a wall thickness of 3.25 mm use over 70% more steel than the frame work to ensure the foundations are as capable of withstanding the forces applied ot them.

1. Crop BarsCrop bars stiffen up the structure during strong winds. They can also help keep the legs tied together under heavy snow. We use large diameter, high tensile steel to ensure the structure remain rigid under both wind and snow loads.Calculations on our ROBUS range show adding crop bars can increase the wind load capacity by up to 60%

7. DoorsAluminium doors are much stronger than timber doors. Timber will deteriorate over the years, whilst Aluminium will perform season after season.Aluminium doors can also be re-sheeted a lot easier than timber doors should the polythene need replacing.

3. BracingsAll our structures are supplied with 50 mm bracing to all corners. Providing large diameter, high tensile bracing in one piece en-sures the structure stays rigid under high wind loads.

9. Door FramesOur door frames are made from 75 mm x 75 mm timber which is tanalised for added durability. All door frame joints use steel plates to add to the joint strength.Our door frames also give extra strength in the gable ends for wind loads.

11. Anchor PlatesA lot of other polytunnel supplier supply ‘commercial’ polytunnels with anchor plates to secure them in the ground.At NP Structures, we will NEVER recommend using anchor plates on a commercial polytunnel.

Ground anchor plates typically require the foundation to be back-filled with loose soil, which is generally a lot weaker than compacted, historic soils. The weakened back-fill makes it a lot easier for the anchor plate to pull free of the foundation. Also the foundations do not just resist uplift, there will be an amount of overturning moment resisted by the foundation due

to side winds, A mass concrete block has both a counter weight and a larger surface area in contact with the existing soil with which to resist the overturning moment, ground anchor plates rely solely on the interaction of the ground tube and the weak-ened back fill to resist the overturning. During winds, the hole is more likely to become tapered, allowing the tunnel to move and flex, therefore creating extra stresses within the components and increasing the risk of failure.

6. FoundationsWe specify a mass concrete foundation for a number of reason, firstly the concrete provides additional protection to the ground tube steel. Secondly, the concrete block increases the surface area in contact with the ground, meaning the resistance to sliding and overturning is massively increased. Finally, the mass of the concrete helps resist the uplift created by high winds. Ground anchor plates are not capable of withstanding the same forces, so we don’t use them.

2. FittingsCommercial grade, weld fittings help keep the structure rigid under high winds reducing wear and tear on the cover, as well as ensuring our structures remain how we design them to be.

8. Hoop SectionsMany other polytunnel companies will supply hoops in 3, 4 or even 5 pieced due to transport restrictions. However, each joint within the structure will create a weak point. They provide ‘optional’ extra parts to strengthen these weak points. These extra parts are often referred to as ‘storm bars’.

Using as few hoop sections as possible keeps the structure as strong as possible. This is why at NP Structures, we will ONLY supply hoops in 2 sections and our hoops DO NOT need ‘storm bars’.

Transport Restrictions.

Because of our 2 piece hoop, 90% of our structures are delivered using our own transport. This allows us to delivery larger items safely and securely. This also ensures your structure arrives complete and in good order.

4. SteelworkAll our framework is manufactured from high tensile pre-galvanised steel to give a stronger structure. Our steel is typically 48% stronger than standard structural steel, with material certificates available on request.

10. Base RailsBase rails are important as they hold the sheet on the structure. The stronger the base rail the tighter the sheet is likely to remain, resulting in a longer life span and better performance during strong winds.

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See what else we do.

NP Structures LtdMill GreenWaterside RoadColneLancashireBB8 0TA

Tel: 01282 873120Fax: 01282 871733

[email protected]

06/12-V1

commercial polytunnels · constructing polytunnels for over 40 years. we now supply com-mercial...

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