The CD225: Design for New Pavement Foundations document provides a design procedure for pavement foundations and is part of the DMRB (Design Manual for Roads and Bridges) suite of documents. The DMRB is responsible for providing requirements and advice documents for the design, assessment and operation of UK highways. The recent CD225 revision (Version 1.1.0 – 2025) supersedes revision 1 (2020) and replaces IAN 73/06 and HD 25/94.

This note provides a summary of the CD225 design procedures and important principles when considering the road foundation as part of an adoptable highway design.