Types of Site

These are the principal types of building sites : 

1. Open fields where the topsoil for many years has been cultivated to a depth of about 300 mm. 
2. Wooded sites where Silurian depth of topsoil be expected. 
3. Reclaimed urban areas, which have been subjected to successive building and demolition for perhaps centuries. 

There are few problems associated with the first type of site, subject lo the bearing quality of the subsoil and the presence or otherwise of a high water table. The second type of site poses more problems. Where trees have lo he cut down in areas to be covered with buildings or roadworks, the whole of the  structure must be dragged out. It is not satisfactory for root growths, which may continue to develop to be left in these positions. The excavations left must be properly filled with hard soil, in layers not exceeding 225 mm thick and well watered in and consolidated by rolling or ramming. 

The third type of site can pose many problems.  It is likely that that the site has been filled in with hard soil which is probably loosely compacted and can contain large voids. It is also possible that old foundations and floor slabs will have been left in mil need to be broken out. Drains and old service pipes will probably  be found, It is essentially that all these problems ace fully appreciated and steps taken to deal with them if the occasion arises, Usually it will be necessary to take  foundations  down to level below that of any original work or filling.