The strip is deeper for greater security...
Simply put, a deep strip foundation is a strip of concrete laid inside a trench. Deep strip foundations usually have a minimum width of 450mm although there may be occasions where a builder recommends a different width. Once this is in then 225mm depth of concrete is needed for the conservatory’s foundation. Sometimes builders will recommend that the strip is deeper for greater security.
There should be no weak soil patches...
Deep strip foundations work well where the ground does not have imported soil or a wide variation in the strength of the soil in the load area (floor area or load of the building). There should be no weak soil patches as this could cause the foundation to fail. The width of the foundation strip has to comply with building regulations. Whether or not you choose to have deep strip foundations is dependent not only on the soil but on the size of the wall that you intend to construct. When deep strip foundations are in the proper place, i.e. not close to trees they usually work well.
Don't work well in areas where the soil is loose...
Problems occur when the trenches are not in the right place or if they are not as straight as they should be. Trenches need to be the exact length and width if you are to avoid subsidence or foundation failure. Most problems that people experience with their building’s foundations occur within the first ten years. Deep strip foundations will not work in an area where there are a lot of trees or when the ground is heavy with clay. Deep strip foundations will also not work well in areas where the soil is loose. Loose soil can lead to the trenches shifting which will lead to failure of the foundation and eventual cracks in the wall.
Deep strip foundations can take a long while to prepare because the measurements for the trenches need to be exact if future problems are to be avoided. Sometimes builders will recommend using reinforced concrete in the trenches as this makes for a more secure foundation.
Related articles: