My barn will be finished within a month.
The tedious bit was finalising a design, the planning application and finding the right supplier. The planning was a bit nerve racking as my whole project and future income hinged on it, so I was careful to have several discussions with the chap who I knew would take the decision and consequently I knew before applying it was very likely to go through OK. I eventually settled on an agricultural contractor who's widely used by local farmers, he's efficient, competitive and I've seen his finished buildings.
I opted for a building that was likely to be as big as I'd need rather than compromising on size, and these buildings tend to go in multiples of 15ft. My originally envisaged 20 x 40 therefore grew into a quite chunky 30 x 45. Its not cheap, but will be a great facility. It incorporates an area to be used for shelter as well as a large parted vented but weatherproof and secure open main area for timber and plant. The whole steel frame is hot dipped galvanized and the exterior will be double clad timber. The floor will be reinforced concrete. The doors are metal and without detailing my measures taken, it will be very secure.
The roof maxes out at around 18 feet at the ridge, is fibre cement, and that prevents condensation creating 'artificial rain' on the inside, as happens with steel roofs. It'll be well lit with plenty of skylights so will have good natural light inside, even without any windows. I pitched the roof at 22.5 degrees and the main part faces due South in the middle of the clearing, so I can put off grid solar panels on the top.
We've had a few delays due to the weather and the contractor having problems with other huge buildings he's doing taking longer than he thought, but its now rattling along nicely. The foundation pads, uprights, roof steel and purlins were done in just two days.