Subsidence and heave affect millions of homes in Britain, with almost 1m in the highest-risk category. With extreme weather conditions becoming more common, the numbers affected are expected to rise. The areas with the highest risk of subsidence and heave are Colchester, South London, Bristol and Glasgow. Within the M25, 40% of all postcodes are classified as being at risk of subsidence or heave. These issues are often made more prominent through adjacent trees which abstract large amounts of water from the surrounding soil which increases the shrinkage rate.
Some clay soils change their volume in relation to their water content. They shrink as they become drier and expand as they become wetter. They act like a sponge. Some types of clay shrink and expand more than other types. Conservatory builders should always take the soil conditions into account when designing a building but rarely do.
The NHBC advise you provide a void under floors to accommodate heave where required along with the use of claymaster type protection to protect the foundation from volume change of the soil. Most conservatory builders simply lay a slab and take little or no heed of the ground conditions.
As a builder of quality conservatories, it is essential that you do not damage your reputation by building on inferior foundations.
Quickbase Foundation Systems are designed specifically to overcome problems of clay heave. The system rests on helical piles, which are driven below the zone of influence of tree roots and subsequent volumetric change in the clay. The smooth shaft of the pile allows the clay to expand and contract without the pile/building being influenced by the movement.