It is a type of fill used in landscaping and earthworks projects. The material is utilised to build up or level out landscaping areas.
The classification and requirements this is detailed in Series 600 of the Specification for Highway Works, a document that provides guidelines on various types of earthworks and materials that can be used.
The definition of Class 4 fill material is intentionally broad, allowing for flexibility in the types of materials that can be used. The Specification for Highway Work simply describes the types of materials are “Various” meaning there isn’t a strict, predefined list of materials.
The guidance document on these states, general or selected fills should be allowed for Class 4 landscape fill with appropriate limits on materials properties being stated in contract specific Appendix 6/1. These limits should draw in those materials, listed within Clause U1A unacceptable material in Clause 601, which would be acceptable as landscape fill.
It also states class 4 is for landscaping and top soiling respectively. Applying common sense to this you can expect soily material should be used but it doesn’t always necessarily need to be.
It should be noted that there are plenty of compaction specifications that the material needs to adhere to.
Sources:
...It Shouldn't Cost The Earth
