Things to consider before building a foundation.
  • By Vincent ,
  • 21 Aug 2018
  •    854

Things to consider before building a foundation.

The foundation is perhaps the most vulnerable part of a building and certainly the most costly to repair. Foundation problems usually start showing many years after construction. So it important that you pro-actively consult with your builder to make sure that they don’t miss something important in their foundation construction.

What can happen when a foundation is poorly designed or constructed?

  • Foundation failure

  • Structural cracks on walls

  • Building failure

  • Floor cracks

  • Damp floors/Flooded Floor


Above ground indicators of soil conditions:

Even without construction experience it is possible to approximate the soil conditions before or after buying a piece of land. You can check the following:

  • Soil type – Some Clay and Silty clay soils have low bearing capacity and are expansive (they expand when wet, contract when dry). Black cotton (clay) soils which when dry are very cracked and when wet are very liquid are a common problematic soil type in Zimbabwe. Sandy soils are usually well drained and give few problems.

  • Excavations – If there has been previously been excavations done on the land e.g. by sand poachers or for refuse dumping; extra care must be taken and you might have to backfill the excavations with soil transported from somewhere else.

  • Construction near existing Buildings – This can require shoring (supporting) of earth and existing foundations otherwise both foundations.

  • Rock Outcropping at building site – This usually indicates the presence of bedrock. Bedrock is good for supporting huge loads e.g. multi-storey buildings. Note however that its bad for excavations, this is especially a concern if you want to build on a hillside.

  • Water – The presence of a lake, dam, wetland or other water bodies indicate a high water table. As the water table moves up and down this can cause the foundation to: (1) settle excessively (making structure sag) (2) float the structure (making it tilt). Also in such instances waterproofing of foundations is required.

  • Level Terrain – If your stand is on level terrain this indicates it will be an easy site work, with fair load bearing ability. But drainage is usually poor. .

  • Gentle Slopes – Are usually very easy sites to work on, and have excellent drainage.

  • Steep Terrain – Steep terrains can necessitate costly excavations. You will also have to consider potential erosion protection. Excessive erosion can lead to scouring of foundations leaving it exposed and weaker. There is also the risk of sliding soils when on steep terrain.

  • Foliage – Some trees and vegetation indicate moist soils necessitating waterproofing. Large trees usually indicate solid ground.

After checking and determining that your stand may have problematic features it is advised to consult a civil engineer before beginning construction, who will do a professional site evaluation. 

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