The NJCECI is composed equally of representatives of three employers' associations and three trade unions who are signatory to the NAECI, under an independent Chairman.

The employers' associations are the ECIA: Engineering Construction Industry Association, TICA: Thermal Insulation Contractors' Association and SELECT: Electrical Contractors' Association of Scotland.

The signatory trades unions are Unite the Union and GMB.

These unions form the National Engineering Construction Committee (NECC) which achieves a single trade union voice.

The structure of membership and the constitution of the NJCECI provide the essentials of a single table agreement and create the standards setting authority for good practice. Continuous improvement in standards has had a positive impact on the safety and welfare conditions of the workforce; and it continues to have a major impact on the performance of the engineering construction industry.