Are MEP plans the same as architectural plans?

No — they are completely separate documents prepared by different disciplines. Architectural plans show what the building looks like and how it is laid out. MEP plans show only the engineering systems hidden inside the walls, ceilings, and floors. Both are usually required for an ADU permit, and critically, they must agree with each other.

What each set actually shows

How the two sets are labeled

Sheet labeling makes the distinction clear at a glance. Architectural sheets are typically prefixed A (A-1, A-2). MEP sheets carry their own prefixes:

• M-1, M-2 — mechanical
• E-1, E-2 — electrical
• P-1, P-2 — plumbing

On a full permit set you will often also see structural sheets (S-1, S-2) and, where relevant, a Title 24 energy report. All of these live in one bound submittal, but each is its own scope of work.

Why coordination matters

The MEP engineer works from your completed architectural plans. The duct runs, outlet locations, fixture placements, and equipment all have to match the room layout, wall locations, and ceiling heights the architect drew. If the architectural plan moves a bathroom, the plumbing and ventilation move with it; if a wall is relocated, the circuits feeding it follow. This dependency is exactly why we ask for your architectural drawings when you place an order — they are the foundation the engineering is built on.

A useful way to picture it: the architect designs the house you can see; the MEP engineer designs everything you can't. Both have to describe the same building, or the plans won't pass review.

Who prepares each set

Architectural plans are typically produced by an architect or residential designer. MEP plans are produced by mechanical, electrical, and plumbing engineers or qualified designers who specialize in those systems. It is common — and often more cost-effective — to use a dedicated MEP provider rather than asking your architect to subcontract the engineering, because a focused MEP team already knows the California-specific calculations, schedules, and code notes a reviewer will look for. The two teams simply have to share the same coordinated architectural base.

What this means for your project timeline

Because MEP follows architecture, the smoothest path is to have a complete, stable architectural set before MEP drafting begins. If your architectural plans are still changing, expect the MEP to change with them — relocating a wall or a fixture ripples into the circuits, ducts, and piping that serve it. If your set is final, we can move straight into engineering. If it is still in progress, reach out anyway — we'll tell you exactly what we need before drafting starts, and our included revisions give you room to adjust as the design settles.

To see precisely what a finished engineering set contains, review Mechanical, Electrical, and Plumbing Plans, or the bundled Full MEP Package. Confirm submittal requirements with your local building department, as they vary by jurisdiction.