The build

A lot of raw materials are being affected, this in an email from Northern Polytunnels who I bought one off:

"Whilst we endeavour to manage the current situation as best we can, unfortunately where we have no alternative but to pass on some of the cost increases, we will reluctantly have to do so. The commodities most affected are steel, polythene, PVC and netting."

Not sure what other materials they would use.

Steel probably