LOD 400 fabrication packages for off-site MEP manufacturing. Duct spools, pipe modules, bathroom pods, and electrical racks — dimensioned, sequenced, and ready for the fabrication shop.
We cover the complete range of deliverables your project requires — modeled, coordinated, and documented to the standard your site team can actually build from.
LOD 300 or 350 models are adequate for coordination. They’re not adequate for prefabrication. The difference comes down to what information is in the model geometry.
At LOD 300, a pipe flange might be represented as a symbolic element at the correct position. At LOD 400, the flange is modeled with actual bolt circle diameter, raised face dimensions, and ANSI or BS pressure rating — because the fabricator needs those dimensions to match the corresponding flange on site.
Similarly, at LOD 350, an AHU is represented with its footprint and connection points. At LOD 400, the connection point geometry includes the exact spigot size, offset from the unit centreline, and flexible connection dimensions — because the duct spool fabricated to connect to that unit needs to match.
We develop models to LOD 400 specifically for prefabrication scopes. Where an existing LOD 350 coordination model exists, we develop the relevant sections to LOD 400 before producing prefabrication drawings. We document the additional information required and confirm it against manufacturer data sheets and installation instructions before proceeding.
We review the existing coordination model, confirm current LOD, and identify sections requiring LOD 400 development for prefabrication. Prefabrication scope boundaries are agreed with the contractor.
Equipment and component data from manufacturer technical submittals is incorporated into the Revit model. Flange dimensions, connection geometry, and material grades are updated to reflect actual supplied components.
Prefabrication-scope sections are developed to LOD 400 including full fitting geometry, support steelwork, connection hardware, and interface geometry at site-assembled joints.
Spool and module boundaries are defined to optimise fabrication efficiency and site installation sequence. Maximum dimensions for transport and site access are confirmed.
Individual spool and module drawings are produced from the LOD 400 model. Drawings include all dimensions, material specifications, finish requirements, and quality control test points.
Where modules contain multiple spools or assemblies, an overall assembly drawing is produced showing the relationship between components and the sequence of assembly.
Drawings are reviewed against the Revit model for dimensional accuracy. A drawing register is issued with the prefabrication package and transmitted to the fabricator.
A shop drawing shows the MEP system layout for site installation — where each element goes and how it connects. A prefabrication drawing is a manufacturing instruction for a specific fabricated component or assembly — it includes all dimensions, materials, and connection details required to manufacture that component in a workshop, separate from and before site installation. Prefabrication drawings are produced at LOD 400; shop drawings are typically produced at LOD 350 or 400 depending on the project phase.
Yes. Bathroom pod prefabrication is a well-established area of our work on UK residential developments. We model the pod structure, pipework, waste connections, and electrical containment at LOD 400, coordinating pod dimensions against the structural frame and facade interface. Prefabrication drawings include pipework stub positions and heights for connection to the rising mains, waste connection points and invert levels, and electrical supply entry positions.
Fabrication tolerances and site interface tolerances are incorporated into the LOD 400 model geometry. Spool and module connection points include the tolerance information required for site assembly — typically a combination of slip joint, flexible connection, or mechanical coupling — specified in the fabrication drawing. Where site conditions require field measurement before final spool dimensions are confirmed, we identify those spools and manage them as site-measured items within the prefabrication package.
Yes. We work with the contractor to sequence fabrication and delivery against the construction programme. Spools and modules are numbered in installation sequence, and the fabrication drawing package is issued in phased batches aligned with the programme. Lead times for fabrication are incorporated into the drawing issue schedule.
Yes. DfMA thinking — designing MEP systems to be assembled efficiently from standardised prefabricated components — informs how we approach LOD 400 model development. Repetitive elements across floor plates are identified early and modeled as standard assemblies that can be batch-fabricated. Connection geometry is standardized where possible to reduce the number of unique fabrication items.
