Building mode is used when players want to access their Player-owned house to start constructing rooms, building furniture, etc. This feature can be accessed from the Options menu in the main game interface. Once "House options" button is chosen, players can toggle Building mode ON and OFF.
When building in OFF mode, house owners can invite friends to visit their houses. Anyone visiting the house will only see furnitures that have already been built. Owners can host parties, duel with others, and serve tea while in this mode. Basically, in this mode, entering the house will be the same as entering any other house or building in RuneScape. By default, building mode is set to OFF. Pets are not allowed to be out in building mode.
However, when building in ON mode, only the owner of the house is able to enter. Other players will be prohibited from entering the house. While in this mode, vacant hotspots appear as ghostly figures of the lowest piece of furniture that can be built there. House owners can also build additional rooms (such as Quest Hall and Portal Chamber) and gardens, by clicking on "Door hotspot"s that becomes available as rooms are created. It should be noted that items from the inventory cannot be dropped while building mode is ON.