What is a pile raft foundation?
A piled raft foundation combines two foundation-building techniques into a hybrid design suitable for specialized circumstances. The raft, or spread, foundation spreads the load of the building across the ground. Think of it as a raft floating on the ground supporting a structure.
Which is better raft or pile foundation?
The most prominent point of different lies in the types of buildings for which they are suitable. Both types of foundation are distinct in terms of design and offer different cost benefits also. For example, raft foundations prove cost-effective in the short-term while pile foundations are built for the long journey!
What are pile foundations made of?
Pile foundations are deep foundations. They are formed by long, slender, columnar elements typically made from steel or reinforced concrete, or sometimes timber. A foundation is described as ‘piled’ when its depth is more than three times its breadth (ref. Atkinson, 2007).
When would you use raft foundation?
They spread the load imposed by a number of columns or walls over the area of foundation, and can be considered to ‘float’ on the ground as a raft floats on water. They are suitable where: Floor areas are small and structural loadings are low, such as in one or two-storey domestic construction. A basement is required.
How deep do piles need to be?
Piles were typically concrete, installed to a depth of 300 mm or more. Houses could be supported fully on piles, or have internal bearer support only provided by piles. External piled walls could be: piles supporting the bearers.
How much does a pile foundation cost?
Pile Foundation Prices
|Pile Material||Cost per linear foot|
|Wood||$13 – $20|
|Steel hollow||$20 – $40|
|Steel H Shaped||$20 – $55|
|Steel pipe filled with concrete||$25 – $45|
What is foundation spread?
Spread foundations are foundations at shallow depths of burial where the ground resistance on the sides of the foundation does not contribute significantly to the bearing resistance. Some of the provisions in this Section may also apply to deep foundations, such as caissons and piers [C6.
Is a raft foundation expensive?
Raft foundations are relatively inexpensive and fast to put down, when compared with other types of foundation. Ground excavations are less onerous than for trench excavations, for example, and the foundation and floor slab can often be combined, giving significant savings on materials and time.
Why pile foundation is used for weaker soil?
Pile foundations are quite effective, especially in weaker soils, for transferring the structural loads into the underlying ground.