MEP Design or MEP Detailing

Compared to architectural and structural disciplines, the MEP (M&E) services domain is typically more fragmented with a two tier design system being established in the sector. In an MEP services project, the key participants include the MEP design consultant (also known as the MEP Design Engineer) and the MEP contractor (which includes respective trade sub-contractors). MEP design consultants and MEP contractors have distinct responsibilities. In an ideal scenario, the MEP consultant remains responsible for developing the MEP design (known as the design-intent) and the contractor takes the role of, spatial coordination (which can be construed as detailed design in some respects) as well as procurement and then managing the fabrication and installation process.

In MEP (M&E) BIM as well as conventional MEP (M&E) CAD drafting approaches, the design consultant receives the architectural and structural design drawings/model from the respective parties during his design tenure for the project - the nature of 'design' in the industry means that several versions will be passed across to the design engineer while he is expected to continue with his design. His/her design-intent is intended to work (spatially that is) with the architectural and structural drawings/models but due to time and financial constraints of the project the MEP consultant’s drawings when passed to the MEP contractor will typically not have enough detail to allow installation i.e. the pre-fabrication and installation details required for installation. The MEP (M&E) contractor will then use his/her skills, knowledge, technical product data and other design data to create a services model that is clash free and that allows efficient installation, ease of fabrication and post-installation access and maintenance.

The MEP contractor will have created MEP (M&E) pre-fabrication models/drawings and installation layouts that feature enough detail required to coordinate the services within allocated spaces; prefabricate racks, modules, and assemblies with efficient runs; and carry out installation without on-field re-work. To achieve this, the MEP contractor will change consultant issue drawings drastically in some cases. When one considers that he may typically resize ductwork, split electrical ladder, use completely new equipment and re-route pipework if necessary, not to mention changes required due to lagging, insulation allowances, easy access to maintainable parts and hanging of services, then it is clear that whilst the design-intent may have been in place, the final design (which will still need to be approved by the design consultant) will change significantly.

To anyone else, and certainly to those in the structural or architectural sector where there may be concept development, design development and construction documentation phases, this effort from a contractor may constitute 'design' as it is in effect further detailing of the initial design. However, in the building services sector this is not referred to as design as the design itself is not affected according to the parties concerned. The MEP contractor is actually extending or progressing the design to create coordinated construction drawings.

So, while MEP design and design detailing may well continue beyond the drawings/models provided by the MEP consultant it is not called 'design' but is known as co-ordination or to be more exact ‘installation ready, spatial coordination’.

The advent of BIM, which is also being utilised by consultants, is seeing greater levels of design detailing in the industry with that MEP consultants (MEP designers) now undertaking more of the drawing role. The nature of 3D modelling implies some consideration for spatial coordination must exist and it is certainly true that consultants are now paying more attention to the creation of detailed design and therefore more spatial coordination. The question remains whether the consultant’s models can be used by installers.

The two tier design (intent) and design detailing (coordination) environment may continue to exist for the foreseeable future which in turn may continue to present timing and financial challenges in an industry where financial control and project deadlines remain fundamental for the industry.