Secular lordly houses emerged as a distinct style in the late 19th century, during a period of relative peace in Bhutan.
Under the direction of an inspired lama the fortress is constructed by citizens who historically participated as part of their tax obligation to the state.
[1] Modernly, however, traditional structures are built by wage laborers, straining the government's ability to repair and preserve dzongs in particular.
As recently as 1998, by royal decree, all buildings must be constructed with multi-coloured wood frontages, small arched windows, and sloping roofs.
[4] Lordly mansions of western Bhutan (Bumthang, Paro, and Trongsa Provinces) appeared in the late 19th century during a period of relative calm.
[4][5] The wetter eastern valleys of Bhutan tend to be steep, narrow ravines, with settlements dug directly into mountainsides.
Sloping, wooden-shingled roofs are pitched but lack rain gutters; there is a growing trend toward metal shingles for their durability.
[4] Bhutanese dzong architecture reached its zenith in the 17th century under the leadership of the great lama Ngawang Namgyal, the Zhabdrung Rinpoche.
Smaller flared chortens in Tibetan style are found in eastern and central Bhutan, often accompanied by a protective wooden superstructure.
The native Bhutanese style is a square stone pillar with a khemar near the top, sometimes accompanied by a ball and crescent to depict the sun and moon.
[5] Mountainous Bhutan has always relied on bridges for travel across its many steep ravines and rushing rivers prone to disastrous flooding.