If you're adding an accessory dwelling unit, a garage conversion, a junior ADU, or a detached new build in the backyard, one of the first things your designer or the building department will ask for is a set of as-built drawings of what's already there. Most homeowners don't expect this, and it's one of the most common reasons an ADU project stalls before it even reaches plan check.
This is a plain-language guide to what as-builts are in the context of an ADU, why you need them, what the drawings have to show, and how a 3D scan turns a multi-day measuring headache into a half-day site visit.
Why an ADU needs as-builts at all
An ADU is almost never a blank-slate project. It attaches to, converts, or sits beside a house and a lot that already exist, and the city needs to see how the new unit relates to those existing conditions. You cannot design a code-compliant ADU, or get it permitted, without an accurate picture of what's already on the property.
For a garage or interior conversion, that means accurate existing floor plans, wall locations, ceiling heights, and window and door openings, so the designer knows what they're working with before adding a kitchen, a bathroom, and egress. For a detached ADU, it means an accurate site plan showing the main house, property lines, setbacks, and existing structures, so the new unit can be placed within the required distances.
Original drawings, if the house even has them, are usually decades out of date, missing, or wrong after years of changes. The building department wants current, measured conditions, not what the house looked like in 1965.
What the as-built set has to show
The exact requirements vary by jurisdiction, but an ADU as-built package typically includes:
- A site plan showing the lot, the existing house, the proposed ADU location, other structures, and the distances between them, so setbacks can be verified.
- Existing floor plans of the structure being converted or added to, dimensioned, with walls, openings, and fixtures located.
- Existing elevations of the relevant faces of the building, which matter for height limits and for conversions that add windows or doors.
- Ceiling heights and sections where the project involves habitable space, since ADUs have minimum ceiling-height requirements.
- Existing utility and MEP locations where relevant, since the ADU has to tie into power, water, and sewer.
Your architect or ADU designer takes this existing-conditions set and designs the new unit on top of it. The more accurate the base, the fewer surprises in plan check and in construction.
ADUs are governed by tight dimensional rules: minimum setbacks from property lines, maximum size as a ratio of the main house, minimum ceiling heights, maximum height limits. A measurement that's off by a few inches can push a design past a setback or under a ceiling-height minimum, and that error doesn't surface until plan check rejects it, or worse, until an inspector catches it mid-build. Measured, accurate as-builts remove that risk.
Where 3D scanning fits
Traditionally, getting these drawings meant someone spending a day or two at your property with a tape measure and a clipboard, then drafting from handwritten notes, with a good chance of a return trip for the dimension they forgot. For an ADU, where the garage is full of boxes and the side yard is tight, that's slow and error-prone.
A 3D laser scan captures the entire property, house, garage, yard, and existing structures, in a single short visit. We walk the site with a mobile scanner, and every dimension your designer could possibly need is in the resulting point cloud: wall locations, ceiling heights, opening sizes, and the distances between structures for the site plan. From that one capture we produce the dimensioned floor plans, elevations, and site plan your ADU designer and the city require.
For the homeowner, that means one short appointment instead of a crew tramping through the house for two days, and an accurate base that keeps the project moving through permitting instead of bouncing back with correction notices.
How the process works
A typical ADU as-built job runs like this. We schedule a single site visit, usually a half day or less for a standard residential lot. We scan the interior of the structure being converted or added to, the exterior, and the surrounding site. Back at the desk, we process the point cloud and produce the 2D drawing set, floor plans, elevations, and a site plan, in CAD and PDF, dimensioned and ready for your designer. Turnaround is typically a few business days.
If you already have an ADU designer or architect, we deliver the drawings in the format they want to design from. If you're earlier in the process, the as-built set is exactly what you hand to a designer to get started.
The bottom line
Nearly every ADU project needs accurate as-built drawings of the existing property before design and permitting can move forward, and inaccurate measurements are a common cause of plan-check delays. A 3D scan captures everything your designer and the building department need in one short visit, and gives you a dimensioned, defensible base to build the project on. If you're planning an ADU or a garage conversion, send us the address and we'll tell you exactly what we'd capture and what it would cost.
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