Demolition costs depend on the size and construction of the building, access for machinery, the presence of hazardous materials such as asbestos, and waste disposal. Licensed disposal of construction and demolition waste, and asbestos removal by a competent contractor, are usually the items that push a demolition budget up.
The physical demolition is often a smaller part of the cost than dealing with what comes out of the building. Construction and demolition waste must go to an authorised facility, and segregation for recycling affects the disposal rate. Any asbestos-containing materials must be identified by survey and removed under the relevant health and safety requirements before general demolition begins.
Access matters too. A detached rural house with room for machinery is straightforward; a terraced or semi-detached property requires temporary support, party wall protection and more hand demolition, all of which take time.