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Civil Engineering/single column pad foundation

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Expert: - 2/4/2010


Question
Hi Arshad, I plan to build a 2 story house in Brazil with concrete post and beam construction and a single column pad foundation all by myself a little at a time using a small portable concrete mixer as most people do there but with help.  Hopefully there will be no cold joints or long days.  The entire house will be 95% masonry as all houses in the area are.....very heavy.  The lot is hard sandy soil 300 meters from the ocean and 25 meters above sea level.  The lot slopes from front to back evenly and the house will be 8 meters wide in front X 11 meters to the back heading down the slope. The lot slopes 1 meter from the front edge of the house to the back edge and the house will be 1 meter off the ground in front and 2 meters off the ground in the back.  Should I position all of the pads at the same level for reasons that there may be related to settling or does it make no difference to place each pad at a lower level than the one uphill to save a little on costs and digging?jr5b6  Also do you think it is necessary to connect each column one to another with a beam low on the columns or pads or both or will the soil itself serve the function that the beams would?  There are no other houses in the area with this foundation, they are all concrete wall foundations.  We need to jack this house up to get a view of the ocean and a wall would be a lot more expensive and heavy.   Thanks very much, David Smith.

Answer
Hi David,

So long as the slope is original ground (i.e. not fill), then you can step the foundations down to save costs. It is a good idea to use ground beams to connect the columns of the lower bases to the bases of the upper ones, so that you get a more robust construction. You can then also design these ground beams to act as supports for any walls that happen to align with them.

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Arshad Khan

Expertise

I can answer any questions to do with civil and structural engineering consultancy and construction industry in East Africa and the Middle East, and specifically with the analysis and design of reinforced concrete structures. My particular expertise is in the aseismic design and optimisation of tall buildings.

Experience

Employment history: 36 years in Construction and consultancy in the UK, Kenya, Tanzania, Uganda, Ethiopia, Eritrea, South Africa, Somalia, Zambia, Austria, Bahrain, Kuwait, Doha and the U.A.E.

Organizations
.Fellow of Institution of Structural Engineers (UK) .Fellow of Institution of Civil Engineers(UK) .Member of the Institution of Engineers, Kenya .Registered Engineer, ERB, Kenya .Member of the Architectural Association of Kenya (Engineers Chapter) .Chartered Engineer (UK)

Publications
•1984: International Conference on the Art and Practice of Structural Design, London •1994: 3rd Int. Kerensky Conference in Structural Engineering, Singapore •2008: International Conference on High-Rise Towers, Abu Dhabi

Education/Credentials
BSc, 1st Class Hons, in Building Engineering, University of Bath, UK MSc in Concrete Structures and Technology, University of London. Diploma of Imperial College, UK.

Awards and Honors
•Science Congress Special Award (for 2-seater Hovercraft - 1968) •Institution of Civil Engineers Award for outstanding performance at Bath University (1975) •Concrete Society Postgraduate study Bursary Award (1976) •Consular Representative for British High Commission, Nairobi. (1995 to 1998) •Examiner for Institution of Civil Engineers Professional Interviews, Nairobi. (1997 to 1998) •Branch Representative in Vienna for PI assessment for Inst. of Struct. Engrs. (1999 to date)

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