Lake Oswego allows one ADU up to 800 sq ft on most single-family lots, with no parking requirement and a possible waiver of system development charges. Serden Group handles feasibility, the pre-application conference, design, permits and construction.
Whether an ADU is allowed in Lake Oswego is usually settled — outside the R-W waterfront zone, it is. The real questions are where it fits around protected trees and slopes, how it connects to utilities, and whether the SDC waiver makes sense for how you plan to use it. We answer those first.
Detached units, attached units, above-garage builds and basement or garage conversions. Feasibility, engineered plans, the city’s pre-application conference, permits, site work, construction and final inspection under one contract.
A standalone unit in the back or side yard on its own foundation — kitchen, full bath, bedroom, and its own entry and address.
Built off the existing house on a new footing line, with a separate exterior door and a code-compliant separation wall.
Converting space you already own — insulation, egress, ceiling height, a new kitchen and bath, and a legal second address.
A second story over an attached or detached garage, with the foundation and shear capacity verified before design starts.
We confirm your zone allows an ADU, map setbacks, trees and slope, check utility connections, and outline whether the SDC waiver fits your plans.
Plans and structural drawings, the required pre-application conference with the city, then the building permit through e-Permitting.
Tree protection and erosion control inspected first, then foundation, framing, utilities, finishes and final inspection.
Why Homeowners Choose Serden
Homeowner Stories
Real reviews, quoted word for word from the sites our clients left them on. Every card links back to that site.
Across 400+ reviews on 9 platforms
Also rated on Houzz, Facebook, Nextdoor, BBB (A+ rating) and Networx.
Read all 400+ reviewsThe project was finished on time and within budget. There was outstanding communication from start to finish and meticulous attention to detail. They are a contractor that goes the extra mile and I would definitely recommend.
Fantastic experience! They renovated my entire home with new floors, a full kitchen remodel, and a bathroom upgrade. The kitchen looks amazing with new cabinets, countertop, and appliances, and the bathroom to shower conversion turned out beautifully. Great quality work, finished on time, easy to communicate with, and their pricing was very competitive. Highly recommend!
We were very happy with the workmanship on our upstairs, downstairs and stairs flooring. Very friendly and were very accommodating to our home schedule and would recommend them to anybody who needs work to be done in their home
Serden remodeled our kitchen, dining room, living room and entry way. Dennis and Alex were especially friendly and easy to communicate with. Every person we had contact with was professional and did quality work. When unexpected issues came up, they solved the problems efficiently so we didn't have to stress about anything. They worked really hard to make sure we were happy at each step of the process. We love our new living space!
I purchased my first home a couple years ago, which was a time capsule from the 60s/70s. I got multiple quotes on getting my house updated. I of course wanted the updates to be budget friendly, but quality enough to last for years to come. Serden Group helped make suggestions that saved me money (to no benefit to themselves). With some of the other quotes I received I couldn't understand where so much of the cost was coming from and the quotes themselves were not clear in what I was being charged for. Serden Group however was very transparent in their pricing. The work they did is absolutely beautiful. Communication was consistent and timely. Their crew is incredibly kind and professional and cleaned up everyday. I think the scariest thing for most people getting work done our their homes is finding a trust worthy company to do so. There are too many occasions of companies having inflated pricing, hidden expenses, shoddy work, or poor communication. If you're looking for a company you can trust and to treat your home with the best care, give these guys a call.
We have used Serden Team for 3 projects. They remodeled our master bedroom and bathroom, refaced kitchen cabinets and built a beautiful surround for my refrigerator so it looks built in and remodeled a secondary bathroom. Their work is fantastic. They are easy to work with and communication is the best. I can trust them to do a great job and do the work properly the first time. Wonderful company and will refer them gladly.
They did an excellent job. They were fast and professional. They installed all new doors throughout my house, raised the floor in my family room and office, installed new flooring, and painted both rooms. It looks wonderful. I will be so happy to use the rooms once everything is put back where I want it. We have more work we want done in the future and I will definitely be hiring these guys again.
Serden did a great job on my vacation home in WA. They transformed the property, I had all my floors and windows changed out. Everything looks beautiful, up to date and modern. I will be using them again to remodel my kitchen and bathroom. The whole experience was easy and quick.
We hired Serden and their team to do a complete remodel of our new home that was very outdated. The work they did was incredible! They were very professional, timely, and the attention to detail on the work is amazing. We are so impressed and highly recommend!
Thank you for your quick response. Also, a big Thank You for helping me make my dream house come true, I never expected my home to become so beautiful. Great job. I will recommend you to my friends.
Serden Group and their crews Had done an awesome job remodeling my house. I am very pleased with the outcome. They were very professional and on time. I would definitely use their service again and recommend them to families and friends.
The remodeling team from Serden Group did a very good and professional job at my home. They completely remodeled the kitchen and all the dining and living areas, everything looks like a brand new home! They also installed new patio cover and deck which we already enjoy. Thank you! I definitely recommend them, they are experts, friendly and know what they are doing.
Serden Group remodeled kitchen and all bathrooms in my house. I am very happy with the quality of their work and the way they were informing me on every stage of the project. They also provided design ideas and suggested colors and materials. I needed the full service from design to completion. I am very satisfied.
Cannot be happier with the outcome of our remodel! Professional and communicative contractors. We will go back to Serden for all of our remodeling needs, other contractors do not compare. Yes- we have wasted time and money on others, before finding Serden.
I recently worked with Serden Group on my condo renovation, which included replacing floors, removing popcorn from ceilings, and replacing kitchen counters and cabinets. I loved working with Dennis and David. Dennis helped with input on the kitchen design and was great in helping to reduce stress. They were patient with me and my questions. Their crew was great. And as messy of a job that it was, they managed to leave the place clean when they left for the night. The work was great, and they care for the space as if it;s their own.
This company did a great job on an extensive remodel of a mid 70s home. They upgraded the electrical, plumbing, removed walls, remodeled the bathrooms and kitchen, and put in all new tile flooring. All the home issues were addressed, and we could not be any happier.
Local Knowledge · Lake Oswego, OR
The rules below come from the City of Lake Oswego’s ADU guidance and Oregon law. We confirm each one for your lot during feasibility.
In Lake Oswego, OR, one ADU up to 800 sq ft is allowed on a lot with a detached single-family home in every residential zone except R-W (Residential-Waterfront); conversions of existing house space may add 200 sq ft. No parking is required. A pre-application conference is required before the building permit, and system development charges can be waived if you record an agreement not to use the unit as a short-term rental. Detached ADUs typically cost $220,000–$380,000 in 2026.
The core limits are simple.
State law limits what can be required.
SDCs can add significant cost, and Lake Oswego offers a waiver.
Most of the cost variation comes from the site.
| Scope | Typical cost | Timeline |
|---|---|---|
| Basement or garage conversion | $90K–$210K | 4–6 months build |
| Detached one bedroom | $220K–$380K | 6–9 months build |
| Two bedroom or complex site | $380K+ | 8–12 months build |
| Feasibility, pre-app and permits | Varies by site | 3–5 months |
Lake Oswego requires a pre-application conference before it issues an ADU building permit. Conferences are usually held on Thursday afternoons about two weeks after you apply. The permit is then filed through the state e-Permitting portal, and the ADU must meet the Oregon Residential Specialty Code.
Before issuing the permit, the city inspects tree protection and erosion control. Homeowners cannot do the electrical work themselves; our licensed trade partners pull those permits.
From First Addition and Old Town to Lake Grove, Westlake, Palisades and Mountain Park — plus West Linn, Dunthorpe and Tualatin. We check each lot for zoning, trees and utilities before design. Our Lake Oswego office is at 333 S State St, Lake Oswego, OR 97034 — design consultations by appointment.
Request your free Lake Oswego ADU feasibility consultation
Please select an option to continue.
Questions? Call (360) 836-7775
Three tiers cover most ADUs we build. Each includes design, engineering, permits, construction and finishes. System development charges are listed separately, since Lake Oswego may waive them.
Ranges are planning figures, not quotes. Your fixed price follows feasibility, a site visit and a written scope.
Both sides of the lake, from 1920s First Addition cottages to 1980s Westlake and Mountain Park homes.
Keep Exploring
Everything Serden Group builds in Lake Oswego, the same service in nearby cities, and the planning guides clients read before they start.
Blog posts will appear here.
Full project gallery will appear here.
Save up to
on your remodel when you call today
Call Now — (360) 836-7775Terms & restrictions apply | Offer valid for projects over $10,000
