Here’s our greenhouse. The wood has a 50 year guarantee but is confidently predicted to be good for 70+ years. I’d say it will not need any treatment for at least 15 years.
Whilst the wooden ones are beautiful, given it can’t be seen from the house, have you considered a poly tunnel? Bear with! Not the usual ones that can be rather flimsy, but a Keder Greenhouse designed specifically for windy, exposed locations?
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