I'm not sure what a ATCO trailer is, but it is a 40x60 steel building that is used for storage. I think in this pic you can see the 10x10 garage door in the back. The 2nd floor is 20x 44 and is canalivered(?) to the back building. There was a OLD garage on the bottem that we had taken down, so whe we built we used the same footer and slab that was there, so I ahve a space of 9ft between the buildings that only has 5ft head room but great for mowers. I would have loved to ran the footers and slab back but it was not in the cards. It made the permit a lot easyer being that I didnot change the footprint of the building.