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Guide to House Foundations

This guide to house foundations explains why house foundations is so important, and how the regulations have changed over the years. House foundations is what provides a structure with a stable grounded platform. It is usually the starting point when building a house. House foundations are designed to evenly distribute the weight of your home. A problem with the foundations can cause uneven settlement, which could result in problems such as subsidence. Follow this guide to house foundations to understand what type of foundation you already have, or may need for an extension.

The Most Important Stage!

Building foundations for homes is the most critical part of any new house build. Mistakes at this stage is very unforgiving, and could lead to costly repairs. To avoid such mistakes, foundation measurements should be double checked all the time. Blueprints should be fool proof and accurate. Communication on site is also vital, ensuring everyone is reading from the same plans.

Types of Foundations

There are four main types of house foundation. The one that is chosen depends upon the soil type in the region where the new build will go.

Strip Foundations

Deep Strip Foundations

  • Least expensive.
  • Used where ground conditions are considered ideal.
  • Trench depth is typically 1m. If you need to dig more than 2.5m, then this technique is not practicable due to the amount of concrete and risks involved. Piling would be the better option in this case.
  • Trench width is typically 600mm.
  • Concrete minimum depth is typically 225mm.

Wide Strip Foundations 

  • Used where ground conditions are not ideal, such as the soil being soft
  • Are used to distribute the load over a larger area.
  • These foundations are reinforced with steel to help reduce the loading per m square.

Trench Fill Foundations 

  • Used where ground conditions are not ideal, such as the soil being too loose or water logged.
  • Ideal for chalk and clay soils.
  • The trench sides need to be firm, therefore the ground type must support this.
  • Avoids the need to brick lay below ground.
  • Trenches are filled with ready mix concrete, approximately 150mm within ground level.
  • Mesh can be used to help reinforce the foundations.
  • More expensive than deep strip foundations.

Raft Foundations

  • Used where ground conditions are stable, but have the potential to become unstable due to disturbance deep down, such as mining.
  • This foundation is actually a raft of concrete.
  • Spreads the load much better than other types of foundation, reducing pressure on the ground.
  • Normally used when trench or strip foundations cannot be used.
  • These types of foundation are usually designed by a structural engineer.

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