There are three types of Hakka dwellings :

1. Phoenix house 五鳳樓
2. Round house 土樓，圓屋 (See pictures above)
3. Piang Fong 平房 (Ping Fang in Mandarin = flat house)

        These three types of dwellings I believe signify the three stages of Hakka migration. It can be supported by the statistical distribution of the different type of houses along the path of migration.
When the first Hakkas moved to Fujian, they were the imperial court officials. They could afford to build the very extravagant houses (Phoenix house) that were modeled against the imperial court. Unless the inhabitants were authorized by the emperor, it is unlikely that they could build the houses in this design with such exquisite decor, without risking their lives for violation of the imperial court.
        In the mid stage, the Hakkas were losing their support and affiliation with the imperial court. They had to compete with the locals on equal (actually less equal) grounds. Failed to have the blessings and protection of the emperor (who was in trouble himself), they were often attacked by the locals. The round houses were built as a very defensive structure to fend off the locals.
In the final stage of migration, the Hakkas were more or less integrated with the locals. There was less need for protection and defense. To befriend with the locals, the Piang Fong were built as a symbol of openness. Piang Fongs also could appear early as the dwellings for the lower class (servants, lower rank officials) who accompanied the nobilities in the southward migration.
        There is some indication as we learn that the phoenix houses were abundant in early Hakka settlements in Fujian. The Round houses were common in upper(eastern) Pearl River of Guangdong, while near the Pearl delta, mostly we see Piang Fong. In my home village in Dongguan, I have not seen Phoenix house nor Round house.
This part was written as a letter in February 1996 to a Korean friend studying Hakka dwellings. It is added to this WEBpage on March 5, 1996.

Hakka Earth Building

Styles and Location of Hakka Earth Building - There are many different types of Earth Buildings in Hakka area. The most popular types are the Round, Square, and Five-Phoenix Earth Buildings. The following styles are found among Hakka Earth Buildings:

Round Earth Building

One of the popular types of Hakka earth buildings is the Round Earth Building.
Click Chinese description of Earth Building (Chinese browser required).
This type of building is round in shape and divided into three classes, small, medium and big. The small ones are usually 2 to 3 stories tall with a single ring. The medium dwelling is usually 3 to 4 stories tall with a large inner open space (single ring) or double rings. The large round building is usually 4 to 5 stories tall consisting of as many as three rings.
The very small round building has about 12 to 18 rooms, the small ones have 21 to 28 rooms, the medium ones have about 30 to 40 rooms, the large ones have about 42 to 58 rooms, and the super large round buildings have about 60 to 72 rooms.
Two-third of the round building are 3 stories high and hold roughly 20 families or 100 people.
The round earth building is a "group-oriented" residence, usually with one main entrance. Its wall is usually around 1 meter thick. The main entrance door is padded with iron sheet and is locked by 2 horizontal wood bars. The wooden bars retract into the walls in order to open the door. In the event the wood bars are sawed through, the locking mechanism is still intact.
Inside the entrance is a huge central courtyard where all the doors of the rooms and inner windows are open to.
At the ground level except the hall and the staircases, the rooms are used as kitchens and dining rooms. The rooms on the second floor are used for storage. The rooms on the 3rd level are used as bedrooms. The rooms in each level are identical. In front of each room, there is an open round hallway and usually there are 4 staircases to move from one level to another.
Thus each family occupies one vertical units with lower level as kitchen, 2nd level for storage and miscellaneous use and 3rd level and above used as bedroom. Sometime there is no open round hallway. Instead, every family has its own private staircase.
A typical room is about 10-13 square meter in size. The larger round earth building has room around 15 square meters. The windows facing outside tends to be small, with the window size at the outer wall smaller and the window size at the inner wall larger enabling wider surveillance from the inside. It is extremely hard for outsiders to come in through the windows. There is usually no window at the ground level.
While the round building is fairly large, it has an inner ring, which is like a round building within a round building. For round building that built earlier than 15th century, they have other defensive features that would counter siege. It is said that during Ming dynasty as Japanese pirates intruded the coastal areas, they always leave the Hakka's Earth Buildings area alone.

There are about over 2,000 Five-Phoenix buildings in Shang Hang county(Western Fujian), over 1,000 buildings in each of the other Western Fukien counties: Yong Ting, Wu Ping, Ning Hua, Lian Chen, Ching Liew and Chang Ting. Across Guangdong province, there are altogether more than 10,000 Five Phoenix Buildings, with majority in Eastern Guangdong. All together, it is estimated that there are 20,000 Five Phoenix Buildings, more than 4 times the Round Earth Building.
Five Phoenix represent five different types of "birds" in five different colors: Pink, Yellow, Green, Purple, and White. It also represent the North, East, South, West and Central section, thus the name Five-Phoenix.
There are variations based on the pattern indicated above: three-hall pattern, two-hall and one side-room pattern, three-hall and two side-room pattern, three-hall and two side-room plus the "curl-back dragon" ³ò龍 (Wei Long) in the back, nine hall and two cross pattern etc. all based on the central axis.
The largest is the nine-hall type. In the same central axis, it is composed of three Five-Phoenix Buildings, usually for the clans that has about 500-700 years of settlement history in the area. The last Five-Phoenix Building is called the Back Building (後樓 Hou Lou), the three central halls in the central axis are called Upper, Central and Lower Room (Ting). There is a field or open courtyard between the last Five-Phoenix Building (Hou Lou) and the second Five-Phoenix Building which is overall about one step lower in level than the Hou Lou. This second Five-Phoenix Building is called Central Tang 中廳, and then across another field or open courtyard, yet another step lower in level, is the 下廳 Lower Tang. Thus we have three independent Five-Phoenix Building, yet on the same axis line, it has three levels of ground height, nine halls (three in each building), aligned in the same axis line.
The most popular variation is the three central-structure (tang) and two side-room pattern. The back tang and left-right rooms are usually of two-story. In front of the building is a semicircular pond, the diameter side of the pond is in parallel with the front building. Between the pond and the building is a field.
Entering the front door, you are in the Lower Ting. The Lower Ting is of rectangular shape where the depth is much shorter than the width. On the left and right of Lower Ting there is one room each, the doors of the rooms open to face the lower Ting. Between the Lower Ting and the Central Ting Tang is an open courtyard. There are also left and right smaller Ting between the Lower Ting and Central Ting. Thus the four Tings shares the same open courtyard and each Ting could see the other three Tings. You have 4 independent Tings of different sizes and yet still form an integrated structure with one another. Each Ting is used for different purpose.
As one enters Central Ting from Lower Ting, after passing through two smaller Side Tings, one steps up half a step to show it is at higher level.
The depth of the Central Ting Tang is about twice the depth of Lower Ting, thus Central Ting Tang is quite a bit larger than the Lower Ting. In the Upper Ting, there are two levels. All the rooms window open to the hallways or open courtyard, facing the central axis line.
The Five-Phoenix Building is usually built facing a river and on a slope. At the back of the building, there is usually a vegetable garden. The front pond is used for washing , irrigating the garden, and for aqua- culture. The roof is usually made of Green "Wa" (瓦roof tiles), and the walls tends to be in white colors