A small city of view lots and real grade
Newcastle is compact, largely built between the late 1980s and the 2000s, and defined by its topography. Many houses sit on ridge and hillside parcels with genuine views west toward Lake Washington and Seattle, and a large number of them have decks, retaining walls and drainage systems that are now old enough to need serious attention.
Deck and retaining work here is not cosmetic. On a hillside lot, a deck ledger that was never properly flashed and a retaining wall that was built without drainage are structural problems dressed up as maintenance items. We check for them at the walkthrough because on Newcastle lots the odds are meaningful.
Neighborhoods we work in
Lake Boren · China Creek · Olympus · Newcastle Hills · Coal Creek · Highlands ridge
Permits and inspections in Newcastle
The City of Newcastle permits residential work in its limits. The area's history brings two site issues up more often than elsewhere: steep slope and landslide hazard areas across much of the hillside, which can require geotechnical review, and coal-mine hazard areas — the region was mined historically, and mapped areas may require additional study before building.
Drainage review also matters more here than on flat ground: what you do with roof and surface water on a slope affects your house and the one below you. We treat that as engineering, not an afterthought.
What we build in Newcastle
- Deck rebuilds with correct ledger flashing, footings and railing detail
- Retaining walls built with real drainage behind them
- Kitchen and bath remodels in 1990s and 2000s ridge homes
- Additions engineered for slope, with geotechnical work where required
- Covered outdoor living space that makes a view usable ten months a year
- Whole-house updates: finishes, lighting, doors and millwork as one package
Newcastle at a glance
- Based in Kirkland — Newcastle is a core service area
- We pull the permits and meet the inspectors
- Written, itemized estimates — no verbal numbers
- Bonded and insured in Washington
- Free walkthrough, written estimate
What Newcastle lets you build in the back yard, in 2026
Washington rewrote the accessory dwelling unit rules statewide, and Newcastle rewrote its code to match. Most of what homeowners here believe about ADUs is two or three years out of date.
| What people ask | Newcastle, 2026 |
|---|---|
| How many you can build | Up to two, subordinate to the house |
| Biggest detached unit | 1,000 sq ft, with director discretion for a single-floor conversion |
| Height | 24 ft detached, 30 ft attached |
| Parking | One space per unit, waived within half a mile of a major transit stop |
| Can you sell it separately | Yes — an ADU may be rented, or sold as a condominium or fee simple within an approved unit lot subdivision |
| Owner occupancy | Not required. Washington abolished it statewide under RCW 36.70A.681 — you do not have to live on the lot to have an ADU, and you may rent both units |
| Who issues the permit | City of Newcastle Community Development |
Worth knowing in Newcastle
Newcastle adopted the two-unit rule in its 2025 compliance ordinance. Washington's ADU law has no small-city exemption — the size of the city changes nothing about what you are allowed to build.
Ready-made plans
Newcastle has no pre-approved plan programme.
Source: Newcastle Municipal Code Chapter 18.31, Ordinance 2025-671, plus RCW 36.70A.681. Checked 4 September 2026. Codes in this region are being rewritten faster than any web page keeps up with — we verify your parcel against the code in force on the day we submit, not against a summary.
Four ways to add a unit — a new detached building, the garage, the basement or a suite inside the house — with a calculator that takes your own numbers: see all four and what each returns →
What it costs: a new detached unit on the Eastside runs roughly $325,000 to $550,000 all in, and advertised "starting at" prices leave out $120,000 to $180,000 of site, utility and permit work. Here is the whole number, line by line →
Building in Newcastle: what works in your favor
- Newcastle handles permits directly with the city — we prepare the package to their requirements.
- Hillside lots with views are common — structural and drainage planning up front saves redesign later.
Statewide, Washington law (HB 1337) is on your side in Newcastle: up to two ADUs are allowed on most residential lots, a detached ADU may be up to 24 ft tall with side and rear setbacks of no more than 5 ft, units up to 1,000 sq ft must be permitted, there is no owner-occupancy requirement, and no parking can be required near major transit.
Rules change and every lot is different — we verify your exact address with the city before any design work. This page is information, not legal advice.
Newcastle questions we get asked
My deck feels bouncy. Is that serious?
What is a coal-mine hazard area?
Do view-lot additions need special engineering?
Nearby areas we serve
Building in Newcastle? Let's talk.
Tell us about your project — we'll listen, come out, and give you an honest number.
Get a Free EstimateGet a free estimate in Newcastle
Tell us about your project — we'll come out, listen, and give you an honest number.
Call or text(425) 866-3940Email: office@nwhomesremodel.com
Hours: Mon–Fri 8:00 AM – 6:00 PM · Sat by appointment
Based in Kirkland, WA — serving the Eastside and Greater Seattle