Why do MEP prices change by square footage?

MEP pricing scales with square footage because a larger ADU contains more fixtures, more circuits, higher mechanical loads, and longer pipe and duct runs — and each of those requires additional engineering, drafting, and calculation work. The price reflects the real design effort, not an arbitrary surcharge.

What actually grows as the ADU gets bigger

• Mechanical: a larger conditioned area means a higher heating and cooling load. The Manual J load calculation must account for more wall, window, and roof area, and the equipment may need to be upsized or split into multiple zones. ASHRAE 62.2 ventilation rates also rise with floor area and bedroom count.
• Electrical: more rooms and appliances mean more branch circuits, additional receptacles to meet spacing requirements, more lighting, larger panel/load calculations, and frequently a larger subpanel and feeder.
• Plumbing: bigger units add fixtures (extra bathroom, laundry, larger kitchen), which means more supply and drain-waste-vent piping, longer runs, additional venting, and more detailed isometric and riser diagrams.

How the tiers map to engineering effort

The same logic applies to single-discipline and two-discipline orders — each tier steps up because the sheet count, schedules, and calculations grow with the unit.

Why size-based tiers are fairer than one flat fee

A single flat price would force owners of small studios to subsidize the engineering of large two-bedroom units. Tiering by square footage means a 550 SF backyard studio pays for a studio's worth of work, and a 1,150 SF family ADU pays for the additional fixtures and loads it actually requires.

This is why we publish the brackets openly rather than quoting case by case — you can verify exactly which tier your project falls into before you order.

What does not change with size

Our included benefits are flat regardless of square footage: two revisions, city corrections, and permit-ready PDF delivery. The Title 24 report add-on is a flat +$240 at any size, and turnaround upgrades are flat fees as well.

To find your bracket, measure the conditioned floor area and check the pricing page, then place your order.