I didn’t want a box valley (they take constant cleaning out) and the doorway in the existing building prevents going too low at that side anyway and I wanted the ridge close to that wall so the door will be nicely lined up with the centre of the greenhouse.
So I built the rear slope at 25degrees (as low as I could risk going but still giving a nice slope so rain will run off it) and the front at 35 degrees.
The front slope is very long (over 3.5m/11.5ft) so I bought in some imported redwood tanalised 4x2 timber - really straight, tight-grained wood without knots which will cope with this span without sagging. The glass panes are quite narrow so we get lots of rafters along the run making the structure stronger again.
I used mahogany for the crested ridge so you never need to think about painting those again to protect them - although we should only think about touching up the paintwork every 5 years or so anyway.
Off to Bristol next week to build a 3m by 4m greenhouse with full-length cold frame.
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