GNOMES HAVE GREAT IMAGINATION as builders and make use of any material that comes to hand. Often they have to disguise their homes of course, so no human passers-by will notice, but it is surprising how many odd corners are left untouched by humans, even in cities. Behind garden sheds and factory walls and tangled banks of bramble, there's many an odd corner where gnomes can build their houses and even mansions, and none but the odd passing cat or mouse will notice.
As a broad rule of thumb, the size of a gnome's home is a measure of how many other gnomes live nearby, because they take turns to pitch in and help build each other's houses on a voluntary basis. The hosts just provide a barrel of beer and an endless supply of pies and the house takes shape around them. The owners do get some say as to what kind of house they want. At least, the others generally listen politely as they outline their vision, but this is often little more than a formality because they then tend just to go ahead and do whatever they think is needed. This accounts for the often rather eccentric look of gnome dwellings and why they usually have at least one room with no doors or windows.
Here we see a group of gnomes hard at work on a friend's house, starting from scratch with raw materials they happen to have found lying around nearby. Gnome houses are rarely this obvious but these gnomes live in a particularly isolated spot surrounded by bogs, so they feel freer than most to express themselves architecturally.