7 Things to consider when buying a Polytunnel

While the list below is not exhaustive, we recommend that you view the structure that you are considering buying.
Stand in the structure and check the quality of structure and fittings. Below are some items to consider when you
buying a structure.  Make sure you are getting the best value and quality for your money!

1. CHECK THE POLYTUNNEL DIMENSIONS:

               When looking at structures, check if the sides are curved from the ground (round-sided) or straight-sided.
             Buyer beware: It can be claimed that there is a straight side of 1m but will have a sudden bend to save on steel so there is
             less standing room at sides or middle of structure.

             If straight sided, check the ridge to ground height (B), and are you able to stand comfortably inside at the sides of the structure (C )?


                                                                                                           
ADVANTAGES of Higher Ground to Ridge Height:  - Better Standing room and more Headroom
                                                                                        - Better Air circulation for plants
                                                                                        - Facilitates the growing of growing taller plants e.g. tomato etc
                                                                                        - Allows for extra growing space for crops suspended from crop supports

                                                                We recommend that you visit and stand in the structure itself to check the quality, heights, sizes etc.

2. STEEL SIZE & QUALITY: 

- Is the steel is high tensile?
- Is the steel galvanised inside and out?
- What is the size (diameter) of steel?

Recommended Minimum Size for 8ft—14ft wide tunnels: 35mm
Recommended Minimum Size for 16ft—18ft wide tunnels: 44.5mm

3. QUALITY OF FITTINGS:

How are the cladding rails attached to the structure? With Nails or with steel plates and bolts?
Ensure that the fittings are of suitable quality and will not deteriorate over time.
The cladding rails are used to attach the polythene onto the structure and good quality fittings should
be used to connect the cladding rails to the structure.

Recommended: Use high quality Steel Pressings, Steel timber plates to join rails together and bolts.

4. TIMBER QUALITY:

- Size of Timber rails: The heavier rails secure the cover to the structure.

   Recommended: 100 x 44mm (4”x2”) c/w laths 50 x 22mm (2”x1”).

- Timber Treatment: Is timber treated for Outdoor use
   If it is treated, it lasts longer.
  
   Recommended: Tanelith-E treated for outdoor use

5. CEMENT: How much cement are you getting?

If your structure is been installed with cement:  Are just the four corners been cemented in? 

Recommended: All foundation tubes including the uprights in the gable ends of the structure
are anchored in cement.

6. What is the difference between CROP SUPPORTS and a CROSS BRACE?

 Diagram A : Steel or Wire is installed close to the ridge                      Diagram B: shows how crop supports are installed
                       and used as cross brace. 
                                                                       with supporting steel down braces.
                   
Diagram A: Cross Brace-Single bar                                                      RECOMMENDED: Diagram B: CROP SUPPORTS c/w STEEL DOWN BRACES
- High up: Unable to use sides of cross brace for tying plants to.                 - Accessible, can be used to attach suspended shelving or for training up plants
- Limited use: Depending on the width of the cross brace,                           - Full Use: both the sides and middle of structure can be used.
  you may be able to use only the middle part of the brace bar                       - Weight Distribution: The steel down braces dissipates the weight of hanging plants from 
  and not the sides.                                                                                             the crop supports.
- Risk of buckling if heavy weight is attached                                                - Extra Bracing power of the crop supports

7. POLYTHENE QUALITY? - GET A SAMPLE

- We recommend that you request a sample of polythene to compare quality
- What is the clarity of the polythene or how clear is it?
  Check light transparency, particularly in the PAR (Photosynthetic Active Radiation, which is effective for the photosynthesis, i.e. 400-700 nm)  

  as it is necessary for the plants growth.
- Excellent thermal effect that limits the drop in temperature during the night or in poor sunlight conditions.
- What are the Mechanical properties of elasticity, tear resistance, tensile strength and resistance to perforation, even at low temperatures.
-
Diffused Polythene: Check how much light is passing through?
  High light diffusion = more than 40% of the light passing through the film is diffused.
- Properties e.g. anti-drip treatment should contribute to the high total light transmission and thermicity, an excellent thermal effect limits
  the drop in temperature during the night or in poor sunlight conditions

-
Where is the polythene coming from? For example: European manufacturers adhere to strict European manufacturing quality standards. 

Recommended:  Minimum 800G or 200 microns polythene film.
We recommend that you request a sample of polythene to compare quality.