This achievement seems almost impossible/quite buggy, but I found a way not mentioned anywhere that worked first try for me. Put your building to be sapped somewhere far away with a hidden teleporter exit near it (I recommend maps with areas you can drop down from that are out of the way), then go as far away from the building as you can, and build the teleporter entrance.
As soon as your building is sapped, go into your teleporter, wrench in hand, and destroy that sapper.