What MEP Shop Drawings Include, and How They Differ from Design Drawings

Design drawings say what; shop drawings say how

The engineer's design drawings show what the building needs: the systems, the equipment, the sizes and how they perform. They are drawn to show intent, not every fitting.

Shop drawings are produced for the installing contractor and show how it will actually be built - every duct, pipe, sprinkler line and tray at its real size and elevation, routed around the beams, the ceilings and the other trades, with the fittings, hangers and supports a fabricator needs. Our MEP shop drawing services cover this for mechanical, plumbing, fire protection and electrical contractors.

The sheets in a typical set

What a set contains depends on the trade and the project, but a mechanical contractor's package usually includes:

• Sheet metal plans with duct sizes, elevations and fittings, floor by floor
• Mechanical piping plans with sizes, slopes and supports
• Duct and piping riser diagrams
• Air-device plans showing every diffuser and grille
• Overhead coordination drawings combining all the MEP trades in the ceiling
• Core-drilling and sleeve plans for the openings in each slab
• Sections and details where space is tight

How they are coordinated

Each trade is modelled in one combined BIM model, and clash detection finds the places where a duct, a pipe, a tray or a sprinkler line runs into something else. The conflicts are cleared in the model before the drawings are issued, so they are not discovered when the materials are already on site. A good clash report groups the conflicts by trade, level and severity so the team can act on it - see what a good clash detection report looks like.

How the review rounds work

Shop drawings are normally submitted by the contractor to the architect or the engineer of record, who reviews them against the design. They come back approved, approved with comments, or for revision and resubmission, and fabrication waits for the approval.

On a building that is released floor by floor, the drawings are issued in many rounds rather than one. Planning for that - and keeping every revision tracked - matters as much as the drawing itself.

A real example

For a new affordable housing building of more than 10 storeys in New York City, we produced the mechanical contractor's shop drawings for the whole building: sheet metal plans with duct dimensions from the cellar to the top floor, mechanical piping plans, duct riser diagrams, air-device plans and overhead coordination drawings combining the MEP trades, plus VRF core-drilling plans for the typical floors and a roof model for clash checking.

The set was issued over about eight months in more than 25 submission rounds as floors were released, reviewed and revised.

What to send your detailer

To start a shop drawing package, a detailer needs:

• The current architectural, structural and MEP design drawings or models
• The equipment submittals that have been approved, with sizes and connection points
• Your company's fabrication and installation standards
• The floors or areas to start with, and the release schedule
• The BIM execution plan and file formats, if the project has them

Try it on one floor

If you are weighing up outside help, start small: send the models or drawings for one floor and ask for a free clash check. You see how the conflicts are reported before committing to a full package.