The absolute smallest building we've ever had, was 20 wide, 50 deep, with a 12 wide by 14 tall door. I would never go smaller, as on this one I couldn't get the awning all the way out when parked in there. This building was sold with the house. If you ever decide to go with a fifth wheel or larger class a motorhome, the 14 foot tall door is the minimum, and 12 foot wide in the mirror of a class a looks more like 10. Plan for the future, or at least don't limit yourself. Suppose you get a 40 foot diesel pusher one day with a 13 foot height. Our Tiffin was between 12-13 foot tall. I've seen way too many people regret the size of their buildings as they wouldn't spend that extra few dollars.
John and Rebecca Dickson
Emma-7 / Little John-5 / Iva-1
Full Timing Again, Rev B
2013 Ford F-350 Lariat CC LB PSD
2015 SOB TT - With OC's Awning Poles (#8)
At least in Heaven, RVs will be perfect, and I won't have to keep fixing them.