ADU construction
Detached ADU construction
in Ventura and Los Angeles County
A second home in the yard, on its own foundation, with its own services and its own front door.
What this covers
A detached accessory dwelling unit is a self-contained second dwelling built in the yard of a property that already has one. It has its own entrance, kitchen, bathroom and sleeping space, stands on its own foundation, and is served by its own water, sewer, power and drainage.
EMAE & Sons Inc works across Ventura, Los Angeles and Orange County. An ADU stands on its own foundation and carries its own services, so the excavation beneath it and the structure above it fall within a single contractor's scope.
- CSLB license
- #1107216 — Class A, B, C-36
- Office
- Thousand Oaks, CA 91360
- Local service area
- Thousand Oaks · Newbury Park · Westlake Village · Agoura Hills
- Recent work
- Newbury Park · Simi Valley
What the work covers
Detached units in a back or side yard
A separate building with its own entrance, kitchen, bathroom and bedroom. A home in its own right rather than a converted outbuilding.
Foundations and site preparation
The pad cut, formed and poured for the unit, including the retaining or shoring work a sloping yard needs before anything can stand on it.
Utilities run to the unit
Water, sewer, power and drainage trenched from the main house or the street, and reinstated afterwards.
Access, paving and drainage
The path, the parking and the drainage that has to work once a second dwelling is sharing the lot.
Units on constrained lots
Narrow side yards, slopes and restricted access, where getting plant and material to the back of a property is most of the problem.
Structural work to the main house
Where the main house has to be altered to suit: a new opening, a relocated service run, or foundation work along the shared boundary.
Design, permits and build under one contract
The drawings and the permit application handled alongside the construction, so the unit is designed, approved and built without the owner holding three separate agreements.
One to three bedrooms
Units from one to three bedrooms with one or one and a half bathrooms, a vaulted living room, and an exterior covered patio.
What decides the cost of an ADU?
The unit varies far less between jobs than the site it stands on. Three conditions account for most of the difference from one lot to the next.
What the ground will carry
A level yard on firm ground takes a straightforward foundation. Slope, made ground or fill has to be cut, retained or founded deeper before the unit has anything to sit on.
How far the services run
Water, sewer and power have to reach the unit. Ten feet of trench across lawn and sixty feet across finished driveway are the same operation at very different cost.
Whether plant can get there
Back-yard access determines whether material is machine-handled or carried. A narrow side return can add more to a job than the specification of the unit does.
EMAE & Sons establishes all three before quoting, and states where a condition has to be investigated first. A price issued without them is a price that will change.
How one gets built
An 880 square foot detached guest house in Simi Valley, from a cleared plot through to a finished room. The same five steps run on every unit; what changes between lots is how long the first two take.
Groundwork
The pad cut and levelled and the footing trenches dug, which is where a sloping or filled yard turns into a cost before anything is built.
Footings and slab
Footings formed and reinforced and the slab poured and finished, so the unit stands on its own foundation rather than on the house's.
Framing
Walls framed and sheathed and the roof decked, which is the point the building stops being a footprint and starts being a structure.
The vaulted ceiling
A vaulted living room changes the framing rather than the finish: the roof carries its loads without a flat ceiling tying the walls together.
Finished
The same room closed in and decorated, with the vault carried through to the finished ceiling instead of being lost above a flat one.
ADU projects
Both units stand in Ventura County, where EMAE & Sons is based, and each carries its own record. One is photographed as a completed home. The other runs from cleared plot through footings, slab and framing to final inspection, and is the only job on this site documented end to end.
Who this is for
Work we are the right contractor for
- Owners adding a detached unit to a lot that already has a house
- Sloping, narrow or awkward yards where the ground work is the hard part
- Units needing their own services trenched from the house or the street
- Owners who want the foundation, the utilities and the building under one contract
What we do not take on
- Garage and interior conversions inside the existing house
- Prefabricated and modular units placed on a pad by others
- Units on a lot where the main house has no capacity for the added services
EMAE & Sons Inc builds detached units as permanent buildings on their own foundations. A unit in Newbury Park was finished this way, with its own entrance, kitchen and bathroom.
Questions about ADU construction
What is an ADU (accessory dwelling unit)?
An ADU, or accessory dwelling unit, is a second and smaller home on a lot that already has a house on it, with its own entrance, kitchen, bathroom and sleeping space. EMAE & Sons Inc builds detached ADUs in Ventura, Los Angeles and Orange County: a separate building in the yard rather than a conversion inside the existing house.
Does a detached ADU need its own foundation?
Yes. A detached accessory dwelling unit is a building and needs a foundation designed for its own loads and for the ground it sits on, not a slab poured on top of a lawn. EMAE & Sons Inc holds Class A General Engineering alongside Class B General Building, so the excavation, the foundation and the unit above it are one contractor's scope.
How are water, sewer and power run to a detached ADU?
They are trenched to the unit from the existing house or from the street, depending on what the property already has. EMAE & Sons Inc carries out the trenching, the underground services and the reinstatement afterwards under the same contract as the building, so the yard is opened and closed once.
Does EMAE & Sons handle the design and the permit for an ADU?
Yes. EMAE & Sons Inc offers ADUs as design and build, which means the drawings are produced and the permit application is made under the same contract as the construction. The owner deals with one firm from the first sketch to the final inspection rather than holding separate agreements with a designer and a builder.
Can an ADU be built on a sloping or difficult lot?
Yes, and it is where most of the cost difference sits. EMAE & Sons Inc cuts and retains the pad, provides access for plant and material to the back of a property, and manages drainage once a second building is sharing the lot. On a constrained site the ground work is usually a larger part of the job than the unit itself.
Related services
Send us the address and a photograph of the yard
The address, a photograph of the yard the unit would go in, and how it is reached from the street. That is enough for EMAE & Sons to tell you what the ground work is likely to involve, how far the services have to run, and what has to be established before any of it can be priced.