Fourth Dimensional House Block (Four-Dimensional Building Extension Blocks) (四次元たてましブロック) is a gadget that is used to extend the size of user house. Doraemon brought out this gadget so that he and Nobita could have a pillow fight without annoying Tamako. However, Nobita used the gadget to convert the Nobis' Residence into a Skyscraper Mansion for rent.
By inserting a "room block" between the first floor and the top floor, a new room will be created between the two floors. When look from the outside the exterior of the house will be the same as the rooms are compressed in 4th dimension.
The 2005 version of the anime also revealed that if the block were somehow removed while there is still a person inside the room, when he exits the room and attempts to go up or down the stair he will be trapped on the same floor like Möbius strip.
- Nobita created a new second floor which Shizuka later used.
- Nobita created a new third floor for Suneo.
- Nobita created a new fourth floor for Gian.
- Nobita created a new fifth, sixth, seventh and eighth floor which Suneo moved to the seventh floor and Shizuka to the eighth. (manga and 1979 anime)
- Nobita created a new fifth, sixth, seventh floor which Suneo moved to the seventh floor. (2005 anime)
- Dekisugi moved in to the third floor.
- Nobita moved Shizuka's floor upward to the seventh floor and add several floors to separate Dekisugi from her, unknowingly knock Gian's floor out of the main mansion.
- Nobita added the rest of the floors (including Gian's) to prevent Tamako from reaching the top floor (his room).