Mat vs Raft Foundation

Structural Layout Vignette and Multiple Choice

Mat vs Raft Foundation

Postby alleycatbabe » Fri Sep 27, 2013 3:19 pm

In some sources it says a raft foundation is a mat foundation & is a shallow foundation.
Yet, question # 91 in the Ballast Q&A says that a raft footing is a mat foundation placed deep in the soil.

So which is it? Are raft foundations shallow or deep?
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Re: Mat vs Raft Foundation

Postby design8d » Sun Sep 29, 2013 8:12 am

From what I have read Mat and Raft foundations are the same. A raft/mat foundation is required where soils have low bearing capacity and have to support heavy structural loads. In high rises, raft/mat foundations can be several meters/yards thick. These types of foundations are used instead of deep foundations systems like piles when subsidence may be present. Think of them as a foundation system used on a building that would normally require a deep foundation system.
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Re: Mat vs Raft Foundation

Postby Mike-SE » Sun Sep 29, 2013 8:53 am

Ballast is wrong. Raft is a shallow foundation system
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