Squaring Polytunnel Foundations

We recommend that the foundations are set out accurately, this will ensure the polytunnel is constructed to satisfaction. 

Use the 3:4:5 Triangle Method to position the foundation tubes correctly. 

This will ensure the ends are square with the sides. 

Any measurement can be used, simply multiply the 3,4,5 by the same number. 

e.g. – 3ft, by 4ft, by 5ft can easily be multiplied by 5 to become 15ft, 20ft, 25ft, or by 10 to be 30ft, 40ft, 50ft. 

For this example, we’re going to keep it simple at 3ft, 4ft, 5ft.

Creating your right-angle. 

1 - Take a foundation tube and install it in the ground where you want your front left-hand corner to be. (facing the front door, the foundation tube you’ve just installed will be on the left corner) ( image 1, A) 

2 – Install a second foundation tube ( image 1, B) in the ground past the length of your 3 measurements (ie, if you’re doing a 3ft length, place the foundation tube 5 ft away)

3 - Take a length of string and tie it between the two foundation tubes ( A & B) so it’s taut. (image 1)

4 – From the original corner foundation tube ( image 1, A), mark 3 ft along towards the second tube. (image 1 B) and place a peg here. ( C)

5 – From the same original foundation ( A), take a second length of string and measure 4ft by making an arc ( image 2)

6 – From the 3ft marked measurement ( C) peg, draw an arc 5ft (image 3)

7- Where the arcs cross is your exact point for your right angle triangle. ( image 4, D)

8- Using the original corner foundation tube, you can now extend your string lines through the exact points ( C&D) for the rest of the foundation tubes.

9 – To double check your measurements, the diagonal measurements across the opposite corners of the polytunnel should be the same on both sides.