The size is 10'x8'. Constructed from oak pallets, scrapped double glazed windows, walls are double insulated and lined with HDC. Floor is oak planks on oak joists and finished with 15mm HDC x 2. The roof has two ceiling windows for added light. The only things I paid for were the screws, electrics, security, and the felt for the roof.
6 months to complete, now with full electrics and 2" thick oak, steel pinned doors with high security mortise locks, 4 hinge bolts per door. Wireless IR security cameras, infra red and standard floodlights.