I came acrosss this practice while living in Istanbul, and prior to working on the Architex. A freind made a film about a man who lived in a Gecekondu. I was intrigued to find a reference in the Atlas of Ownership to a site near the Astral Ship in North Wales - atlasofownership.org 
The Ugly House in Snowdonia was built using the old Welsh custom of 'Tŷ unnos', which means 'one-night house’. The custom says: > That if a person could in one night construct a dwelling, without disturbing the supreme authority (in this case the officials of the landowner of the privately owned estate) they could claim rights to the land and the dwelling.
We don't know for certain why the house had to be built during the night - however it is likely that the process had to be a secret one, and if nobody noticed the house popping up overnight then the new homeowner could pretend that it had been there all along.
The practice of the one-night house in Wales began in the 17th century and continued throughout the 18th and 19th centuries.
At the time, most of the land was enclosed within privately owned estates by the gentry and aristocracy. Scottish records reveal that 3% of the population had legal rights to land in the 18th century.
The one-night house custom was also a way for landless people to claim a piece of land to make a home, and to escape the suppression of land monopoly.
# Legal context
One-night house has no basis in English common law (established in Wales in 1536) or medieval Welsh laws and it existed before the planning system was established in the UK in the 20th century.
Interestingly, examples of the one-night house tradition are found in informal settlements in Colombia, 1950s northern Italy, Bresse region in eastern France, Cornwall and Gecekondu in Turkey across many other legal contexts; old Germanic law, Roman law and old Ottoman law.
The French scholar G. Jeanton suggests that the one-night house custom likely derived from ancient Indo—European folklore.