Handling a gradient

Flattening an uneven site does not appear logical either ecologically or economically

Reality: The levelling cost added with foundation in greater depths hikes the budget.

One aspect where all of us — owners, builders and designers — need to be blamed is for the habit of destroying nature by constructing on undulating locations. Traditionally our country believed that sites should be in an unaffected level, strange in a nation of gently sloping regions, rolling plains and low hilly terrains. So, what we do is to cut the ridges, fill the valleys and level the uneven.

Even in the historic homes of the west coast where we notice raising verandahs in 2 or 3 levels, the ground had to be flat. The back filling of soil into the plinth must have been humongous, demanding large labour and cost. The ground water flow, disturbed, must have eroded soil elsewhere causing unwanted headache. The levelling cost added with foundation in greater depths must have hiked the budget. The possibility of creating a building elevation, growing taller and majestic, must have got lost.

Building in different levels

Have we learnt our lessons? Not really. We can build up the foundation in steps, corresponding to the site gradation, instead of it going down to the same depth everywhere. Better still, we can plan the building itself in different levels. By skilful planning and careful alignment of the structure to the natural site levels called contour, we can not only avoid unwanted cut and fill, but also keep the foundation depth to the minimum.

Designing with parallel load-bearing walls could be considered, where the cross walls need only a nominal support. In traditional homes with wood joist roofs, it was common to have a full-fledged foundation only for those walls which take the joists. Today, in RCC design, we can replace this system by one-way slab design. If these walls taking the slab load are running parallel to the contours, required digging can be further reduced.

In coastal Karnataka, the practice of proper foundation for the external walls with nominal ones inside the plinth is still prevalent.

In case of varying slopes within a larger site, providing plinth beam could be another simple system, where deep foundation trench can be avoided where soil is loose and uneven. Also, the engineer may advise us to execute a soiling course, primarily a large stone base to strengthen the soil condition. Of course, it is advisable to get the expert opinions and construction cost compared before jumping to a conclusion.

Anyhow, flattening the site does not appear logical either ecologically or economically.


Posted on May 29, 2010, in fundamentals. Bookmark the permalink. Leave a comment.

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