London
OK, finally able to post this after seeing so many great ones here - thank you for the inspiration and helpful tips. I'm based in the UK, so £, metres and many other linguistic compounds may be used that you may or may not understand will be used 
I had a external building at the bottom of my garden that was to be for something else. Anyway I ended up hijacking it and it would take 6 machines in but I kept buying more machines, with three in the house, two at my office, 6 in the room and a bunch in the garage. Looked to buy a bigger house but couldn't find anything I liked enough; considered extending my current house but couldn't figure away to do it that worked with the existing building but then I saw an epic video of a "pinball shed" not far from where I live and googled for it and found a build thread over on pinballinfo (UK forum). Julian the guy who built it was kind enough to let me visit, that was a bad move lol, as soon as I went to see it I knew thats what I needed to have. His shed comfortably fitted twenty games and could probably fit thirty uncomfortably.
Julian was kind enough to share his details but he did his a few years ago and a few things had changed, key thing being the exchange rate which made the shed a lot more pricey so I decided to shop around a bit more. I narrowed it down to three shed vendors and let them convince me. One company stood out and whilst not the cheapest (to be honest money was a secondary concern but nobody wants to be ripped off right?) they had done some huge builds for school halls etc and feedback was positive. So I went with them; they are called Keops; I'd recommend them with one or two caveats. I went for a dual skin log cabin.
So September last year I applied for planning permission, here in the UK you can't just build what ever you like, the planning process is sub-optimal but by the end of the year it was granted although I had to get a special tree report; planning cost me just under £2000.
Because of the size of the room certain building control regulations apply around insulation, electrical and foundations. To qualify this, I spent more money on insulation than I did on the actual materials to construct the building! Fortunately the cabling for power was fine and I was able to reuse this which game me . The building included 200mm roof insulation, 100mm floor, and 80-100mm all around.
The picture with red flooring is my to rough scale initial plan. I was including a small area for a gym for my wife but increasingly thats ended up somewhere else
This finally turned into the scale drawing attached.
So first thing I had to do was remove my existing games and store them in the house. Backbreaking fun
IMG_7858-2 (resized).JPGIMG_7859-2 (resized).JPGIMG_7860-2 (resized).JPG
So did this just after Christmas - install date for the cabin was February. But I had to demolish the existing room in-time for the foundations to be installed.
Foundations turned out to be the hardest part of this job. First building control had limited guidelines on this approach and I was worried they might make me go super deep but in the end I was able to build a concrete raft foundation, 20cm crushed concrete followed by 15cm of poured concrete with steel reinforcing mesh and vapour barrier. but first I had to demolish the old room:
I did a lot of it myself but this building was a SPS panel built and I was worried about the roof coming down on me so I got the help of a couple of demo guys for a few hours- they were spot on. Once thing I totally under-estimated was the amount of crap I had to get rid of and spent a lot more on skips (containers) to take crap away from the site.
But the good news is that I had demolished the old site just intime for the foundation guys to do there thing...
part 2 soon...
)
