Introduction: DIY POLYTUNNEL / GREENHOUSE
In 2013 one of our suppliers left behind and modular aluminium exhibition stand after an open day at my work. They then told me that it was to be replaced and just to skip it. However, as it was modular and put together with bolts/wing nuts and contained both curved and straight sections it got my mind working as to how I could use it up at my allotment. Then when I started playing around with it, it made 2 perfect sized arches and I knew then what it was going to be.
In the end we built a 4.3m Long x 2.5m Wide x 2.5m High Poly Tunnel and spent around £87.00.....Not bad!
Tip........It pays to ask local business for old unused, 2nd hand or discounted product, don't be shy!
UPDATE......Since building it we have added additional ventilation and filled the walkways with 2 layers of old monoblock, free of course. The idea was both to make walking easier as the walkways were narrow and to store heat during the day and give it off as it got colder, even if it was only for a short period of time.
LOCATION: Harburn Allotments, West Lothian, Scotland. The site is on the outskirts of West Lothian and at an elevated, exposed area so can get VERY windy.
BUILD DATE.........May 2014
TODAY........Jan 2020 and the Polytunnel still stands using all original materials. We've had to repair the odd tear and hole with poly repair tape and a couple of the external boards need replaced soon. However, consideration location and weather it's held up very well thus far.
Aluminium arches - Suppliers old exhibition stand left at my work and heading for landfill
Blue Poly Pipe Arches and Struts - 32mm water pipe - Old excess pipe free from our Allotment landlord
Yellow Pipe Insert/Fixings - 25mm gas pipe - Left over pieces/cut offs from raised bed arches
Scaffold Board Bracers, Shelves and Bed Walkways - Free from local scaffolding company
Timber Poly Pipe Bracers and Timber For Fixing Poly - £12.00
Vents - £12.00
Vent Insect Netting - Free from local scaffolding company
Sand/Cement For Securing Aluminium Arches - £8.00
2nd Hand Polythene Sheeting from local Pick Your Own Farm - £25.00
Hot Tape - £22.00
Decking Screws/Staples - £8.00
Paint - Spare paint leftover in my shed at home
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Step 1: STEP 1 - Fixing the Aluminium End Arches
1) Each arch built up with an 'L' shaped piece at the bottom of each leg.
2) The arches were temporarily sat in their final positions to mark ground areas were we needed to dig the holes for each leg.
3) The four holes were dug to the depth of the 'L' pieces and the arches inserted.
4) We then used old scaffold boards as bracers to secure each arch together and ensure the frame was level and square.
5) We then back filled the holes with sand and cement to about 90% and the rest with earth.
6) We then put a 'T' braced along the top to ensure the structure was rigid and let the cement set the frame into place.
Step 2: STEP 2 - Creating the Polypipe Arches
1) We used blue 32mm MDPE Poly Pipe to create the intermediate arches to mimic the shape of the end arches and also the upright straight intermediate pieces in the lower half.
2) We used some off cuts of yellow 25mm MDPE Poly Pipe to create joining pieces. This was done by cutting the pipe to the desired length (approx.4"/100mm), cutting it with a hacksaw 50% of the way through and then inserting the other 50% inside the blue 32mm pipe. Couple of screws to fix it into the blue pipe and then we splayed the yellow pipe side ways and fixed to the bracer boards with a couple of screws at either side.
3) The Poly Pipe arches however needed to be braced together in the middle to ensure they didn't pull off to either side when it came to putting on the polysheet and pulling it tight. We done this using a length of treated rough timer for each side bought from a local timber merchant and screwed each poly pipe arch into it.
Step 3: STEP 3 - Creating the End Frames and Base
1) We utilised the bracers by then turning them into shelves.
2) The back end supports were created from scaffold boards and screwed into place.
3) The base was then divided into 3 growing areas and walkways left at either side of the central growing area.
4) The front supports and door frame were then screwed into place.
5) Painting the wooden frame as we went.
Step 4: STEP 4 - Hot Taping and Fitting the Polysheet
1) We used hot tape on all the areas of the frame (well almost all) that the polysheeting would come in contact with as it reduces friction and wear on the sheeting.
2) On a day when it was calm, well slightly breezy, it is Scotland after all so calm is rarer that hens teeth, 3 of us fitted the Poly to the frame and used more scaff boards to brace it to the internal brace boards.This was by far the most challenging part of the build but we got there in the end, determination and perseverance were the key.
Step 5: STEP 5 - Door and Ventilation
1) Again we used scaff boards to create the door and cut the window space out which we then lined with poly, but later on removed the poly and put in mesh for extra ventilation instead.
2) We also cut out a top section of the door and fitted a grate vent with mesh.
3) Finally we cut holes in 2 off the rear sections of the end frame and added 2 grate vents and again at a later date we cut out 2 sections of the end frame poly and added more ventilation that could be covered or uncovered as needed.
4) Entrance mono blocked using old reclaimed monobloc.
Note: Ventilation is key, at the start when we first completed the poly, temperatures were reaching 50C+
FINALLY WE GAVE ALL WOOD A SECOND LICK OF PAINT AND JOB DONE.....