According to Official Guinness Records,
The fastest time to build a house in Minecraft, on a tablet, is 3 min 2 sec and was achieved by Tristen Geren (USA), in Fredericksburg, USA, on 5 October 2015. This Minecraft challenge is part of the Gamers 2016 Annual mega-Minecraft spread.
For a complete list of 2015 records, please visit 2015 Guinness Records in United States.