It does not matter if you are building your accessory dwelling unit with a modular company, or a custom backyard cottage with a traditional stick-built builder, you will need to get the building permit from your city. There is no escaping this cost. It might be hidden in all-in-one price. But it is there. And the total cost of getting the permit might be anywhere between $20,000 and $30,000. That is assuming you have not hired a famous architect. If you have, you will be paying even more.
Some builders call it “soft” costs, while they refer to construction costs as “hard” costs.
The industry term is pre-construction. This is the only phase of your project where you have the chance to save money. This is the phase where the scope of work is determined, and the rest follows. As soon as the construction detail gets into the plan set and then gets permitted, any change order will lead to project delays and cost overruns.
Feasibility study starts in your backyard.
It includes the analysis of your city regulations, site analysis, understanding height and size restrictions, and, in general, looking out for the red flags that could become roadblocks on the fast lane towards an ADU.
The cost of it differs from $500 to $5000 depending who you ask.
Site survey can cost you anywhere from ~$2500 to ~$7000+ depending on the size of the lot and the amount of information of record the surveyor has on your property. You might be tempted to skip this step, however, if you are building anywhere close to property lines you really should not. It is messy business to find out in the middle of construction that you are encroaching on the neighbor’s property.
Additional complication is easements. The city will not allow building on the easement, and it is really silly to draw the plans first only to find out that you cannot build a 1000sf unit you had set your heart on because some oil company has easement across your property (happened before, you know, though utility easements are more typical).
If you’re planning to build an ADU (Accessory Dwelling Unit), a backyard cottage, or any addition close to your property line, there’s a good chance your city or county will ask for a land survey before issuing permits. Most jurisdictions now require one, especially when a new structure sits near a setback.
The reason is simple: everyone wants to make sure you’re building on your own land. But when homeowners start getting quotes, something surprising happens. Two neighbors on the same block can get very different prices for what sounds like the same service. One pays a modest fee for a quick boundary survey. The other is told they need a “Record of Survey,” which takes longer and costs more.
So what’s going on? It all comes down to how your property was described on paper long before you bought it.
Think of it this way. A boundary survey is the work. A surveyor goes out, does the research, and figures out where your property lines are. A Record of Survey is a formal map of that work, filed with the County so it becomes part of the public record forever.
Every Record of Survey starts with a boundary survey. But not every boundary survey has to become a Record of Survey. Which one you need depends on your deed.
Some properties sit on a complete original lot. The deed reads something like “Lot 7, Block 3, Maple Grove Subdivision.” That entire lot was already surveyed, mapped, and recorded at the County when the subdivision was first created, sometimes 50 or 100 years ago. The four corners already exist on an official map.
In this case, a surveyor can usually just locate the existing corners, mark them, and confirm the lines. No new map needs to be filed. This is the faster, cheaper version most people picture when they hear “property survey.”
Other properties are a little different. The deed might read something like “the westerly 40 feet of Lot 7 and the easterly 20 feet of Lot 8.” At some point in the past, someone carved up the original lots with a deed description, but no surveyor ever went out, officially established those new dividing lines on the ground, and filed a map showing them.
Under California law, whenever a surveyor has to establish a boundary line that isn’t already shown on a recorded map, they’re required to file a Record of Survey. This means more research (including checking the neighbors’ deeds to make sure everything lines up), drafting a map to strict County standards, a County review that takes several weeks, and setting physical markers at the corners.
It’s more work, and yes, it costs more. But it’s not the surveyor upselling you. It’s state law.
If you’re building an ADU close to the setback line, a Record of Survey gives you real protection:
When your house sits just a few feet from the property line, you want the strongest possible paperwork backing you up. A Record of Survey is exactly that.
Before you ask for quotes, pull out your deed (or grant deed) and read the property description. If it refers to a clean, whole lot, you may only need a standard boundary survey. If it refers to a “portion of,” “the northerly half of,” or combines pieces of multiple lots, expect a Record of Survey.
Either way, share the deed with your surveyor upfront. A good surveyor will tell you honestly which type your property needs and why. That one conversation can save you weeks of confusion later, and it will help you budget accurately for the pre-construction phase of your ADU project.
Building close to the line is completely doable. You just want to make sure the line is exactly where you think it is.
Are you looking for a simple off the shelf solution? You can go with a modular company that has design baked into the product. As long as you like the layout, its exterior finishes and the company can crane the unit onto your property, you gain thoughtful design and speed of construction.
Some architects also sell ready to go plan sets for custom builders, with structural engineering, Title 24 calculations included. These usually run around ~$8000+. In this case, you get the stamped plans ready to be submitted – but no changes. All the additional tweaks will be at the architect’s hourly fee.
If you have some specific design requirements, then it might make sense to go custom and work with the architect or designer of your choice to develop a unique solution.
Make sure the architect includes a CalGreen checklist, a requirement for all newly constructed buildings.
Structural engineer will charge you ~$3500 for a simple ADU project.
Grading and drainage plan will cost you ~$3000 more.
For energy calculations, a.k.a. Title 24, add ~$400.
You might need an arborist if you have any heritage trees that need protection – add ~$1000 to the bill.
Your estimates may differ – every backyard is different.
Printing costs should not be discarded either, I have recently paid ~$200 for the five paper copies of the plan set that I had to deliver to the city along with the corresponding pdf file.
City permit submittal costs hide different types of fees:
Recovery fees are paid for the time spent by the planner on your case.
An impact fee is imposed by a local government on a new or proposed development project to pay for the costs of providing public services. Impact fees have become an essential part of local governments to fund infrastructure and go towards the development of needed parks, schools, roads, sewer, water treatment, utilities, libraries, and public safety buildings. Most of them waived for units under 750 sf.
It might sound illogical that you will be charged for connection fees, as you are adding a secondary building, so all main utilities are already there, right? Well, a certain Bay Area county had charged a homeowner a whooping $36,000 for a water connection. Go figure.
Starting at $14,000
Starting at $11,000
Starting at $18,000