Prefab ADU cost in Woodland Hills is often quoted as the price of the unit alone. The unit is only one line. A factory-built ADU still needs a foundation, a way onto the lot, utility connections and a permit, and those lines are the same kind of work a site-built unit needs. The useful comparison is the full cost of each path on your lot, side by side, and that is what we put in writing.
Two ways to build the same unit
On the site-built path, a crew frames the unit in your yard on a foundation poured there. On the prefab path, the unit, or large sections of it, is made in a factory, trucked in and set on a foundation poured there. Either way, a crew digs, pours, trenches, connects and finishes on site. What changes is where the walls and roof are put together and how they reach the back of the yard.
On a Woodland Hills parcel, the choice usually turns on the lot more than on a catalog. A flat yard with a wide side access suits a delivered unit. A yard behind the house with only a gate and a rise suits framing in place. Send us the address and a photo of the route from the street to the back, and we will quote both paths for the same unit once we have walked it.
What sets the price on either path
The unit. On the prefab path, the factory price covers what the factory makes, and its spec sheet says where that ends. Check whether it includes the foundation connection, interior finishes, appliances and delivery. On the site-built path, the shell and finishes are priced by us as lines of their own, so you choose each one.
Foundation. Both paths need one. A delivered unit sits on a foundation designed for that unit, often with set points given by the maker. A site-built unit gets a slab or raised floor drawn for the lot. Slope and soil drive this line on either path.
Crane and delivery. This line exists only on the prefab path, and it can be large. The truck needs a route to the curb, and a crane needs a place to stand and a clear swing over the house, wires and trees. Where the swing is blocked, the unit may have to come in smaller sections or may not fit at all. Framing in place avoids the crane but brings more deliveries and more crew days on the lot.
Utilities. Sewer, water and power reach the unit the same way on both paths. Trench length, the depth of the lateral and spare room in the panel set the cost. A factory unit arrives with its connection points fixed, so the trench has to meet them where they are.
Permits. Either path goes through plan check for the lot. A factory-built unit still answers to the building department, and we find out which permits and reviews it wants at your address. The site plan, foundation and utility connections are drawn and permitted on both paths. On the site-built path, a plans package is available for qualifying small one-story ADUs.
Decisions that change the scope
A few choices decide which path comes out ahead on a given lot. Setting the unit closer to the street can open up crane access but gives up yard and privacy. A two-story unit narrows the factory options and adds structure on either path. A custom shape that fills an odd corner favors framing in place. A plain rectangle that matches a factory module favors prefab. A rental with its own meter adds utility company work on both.
The schedule shifts too. Factory work can run while the foundation is poured, which can shorten the time a crew spends in your yard. Site-built work starts once the permit is in hand and runs in sequence. We show both timelines with the quote rather than promise one.
If you already bought a unit and only need the site side, or need part of an earlier job redone, we will look at that as well.
How the visit and written quote work
We start at the lot. We measure the access from the street, look up at wires and tree canopy, check the grade, find the sewer cleanout and read the panel. If you already have a factory unit in mind, bring its spec sheet and foundation drawings to the visit.
The written quote then sets two columns next to each other: prefab and site-built. Each column lists foundation, delivery or framing, utilities, permits and fees, and finishes. Items that would be paid to the factory on the prefab path are marked, so you can see what sits outside our contract. Any line that depends on something we cannot see yet is named along with how we will check it. If one path will not work on your lot, its column says why.
What to have ready
- The property address, plus a survey or site plan if you have one.
- Photos from the street to the back yard, including the side yard, the gate, overhead wires and trees.
- The spec sheet and price breakdown for any factory unit you are weighing.
- The size and room count you want, and whether the unit will be rented.
- A photo of the electrical panel with the cover on.
Our ADU construction page covers the four unit types, and our structural work page explains foundations and retaining walls on sloped yards. Owners weighing a unit against more room for the household can see room additions. Local notes are on our Woodland Hills page.
Price both paths with one visit
Call us or send the form with the address and photos of the access. We will walk the lot and send one written quote with prefab and site-built side by side.