Dire necessity led to this DIY Polytunnel installment. We used 3/4 inch PVC pipes, 36 inch long rebar to make this 24 x 14 ft greenhouse. We got the design off http://www.garden.org in the How-to section.
First we hammered in the 36 inch rebar, so that only 10 inches were exposed above grade. Along each side, the rebar is 4 ft apart. The PVC pipes fit snugly on the rebar forming the arcs of the polytunnel.
Normally the crossbeams are connected with the arcs using 4-way connector pieces. These are not sold locally, so we just tied the crossbeams tightly with wire to stabilise the structure without 4 way connectors.
Then we attached our shade cloth for a fully functional nursery.
We were lucky enough to have a Virgo librarian volunteer to organize our greenhouse!