Renton Steep Slope Homes: Skyway, Renton Hill and Earlington

Renton steep slope homes are concentrated in fewer places than the hills suggest. When we laid the City of Renton’s slope atlas over 5,064 single-family lots in Earlington, Renton Hill and Skyway-West Hill, the steepest grades clustered on a handful of streets: the NW side of Earlington, Renton Ave S and Cedar Ave S on Renton Hill, and the bluff above Lake Washington in Skyway. Most of Skyway’s 4,126 lots have no steep ground mapped at all.

At The Rache Team we have guided Renton buyers and sellers for more than 26 years, and the hill neighborhoods are where the views, the larger lots and the questions are. So on October 20, 2026 we downloaded the city’s regulated slope, landslide and coal mine hazard layers, along with King County’s 2016 landslide maps for Skyway, and checked them against King County’s parcel boundaries. This guide reports where Renton steep slope homes sit, what the city and county codes say about building near those slopes, and how to check one address.

How Renton Steep Slope Homes Are Mapped

Renton’s code sorts hillsides into two classes, and the line between them is the number most buyers never hear. Under RMC 4-3-050, a sensitive slope has an average grade of 25% to less than 40%. A protected slope has an average grade of 40% or more with at least 15 feet of vertical rise. Engineered retaining walls are excluded. A 40% grade rises four feet for every ten feet across, about 22 degrees.

The code says where the boundaries are: the city’s COR Maps viewer, which draws them from the City of Renton Steep Slope Atlas. It also says the maps are a general guide. The actual presence and extent of a slope on a specific site is identified in the field by a qualified consultant and confirmed by the city, and an applicant’s professional may substitute boundaries drawn from a survey.

King County, which regulates Skyway, uses a single class. KCC 21A.06.1230 defines a steep slope hazard area as a slope of 40% or more over at least ten feet of vertical change. The county also maps landslide hazard areas separately, under a definition that includes slopes over 15% with layered impermeable soils and springs or seepage, and any area that has shown movement in the last 10,000 years.

One note on our method. We counted lots, not houses. A lot counts as steep here when at least a tenth of its area falls in the atlas’s 40%-or-steeper bands. The atlas is a terrain model, so it does not test the 15-foot rise and it can pick up a cut bank or a rockery. Treat these figures as where to look, not as a determination for any one property.

Renton Steep Slope Homes in Earlington

Earlington has the most hillside of the three. The neighborhood sits on the face of the West Hill above the valley floor and the airport, and 338 of its 709 lots (48%) have a tenth or more of their area at 25% or steeper. The two halves differ sharply. In the north half, around the NW streets, 94 of 344 lots have a tenth or more at 40% or steeper. In the south half, around Langston Rd and the SW streets, it is 11 of 365.

The steep lots run along NW 6th St, Lind Ave NW, Seneca Ave NW, Stevens Ave NW and NW 2nd St. The city’s landslide layer puts 278 Earlington lots (39%) in a high landslide hazard area, led by Lind Ave NW, Seneca Ave NW, Stevens Ave NW, Maple Ave NW and SW Langston Rd. In Renton’s code, high landslide hazard means slopes over 40%, or slopes of 15% to 40% on soils that are not glacially consolidated or with adverse groundwater conditions such as seeps or springs. One lot on Taylor Ave NW touches a very high landslide hazard area, the city’s class for mapped landslide deposits.

The trade is visible in the county record. Earlington’s steep lots have a median size of 9,894 square feet against 7,200 for lots with no steep ground, and 44% carry a view rating. Our Earlington neighborhood guide covers the rest of the hill, and Earlington vs Skyway compares it with its neighbor across the city line.

Renton Steep Slope Homes on Renton Hill

Renton Hill rises straight up from the Cedar River, and almost half of it is sloped: 108 of 229 lots (47%) have a tenth or more at 25% or steeper. The steepest ground is narrower. Twenty-four lots have a tenth or more at 40% or steeper, twelve on Renton Ave S and eight on Cedar Ave S, with the rest on Beacon Way S and Mill Ave S. Every one of those 24 lots carries a view rating in the county record.

Landslide and Erosion on Renton Hill

Renton Hill reads differently from Earlington on the landslide map. 169 lots (74%) touch a medium landslide hazard area and none touch a high one. Renton’s code defines medium as slopes of 15% to 40% underlain by glacially consolidated soils. 108 lots (47%) also touch a high erosion hazard area, which the code ties to soils with severe erosion potential on slopes over 15%. That matters most during construction, when the city requires erosion control plans.

Coal Mine Hazards Under Renton Hill

The layer that surprises most buyers here is not about slope. On the city’s coal mine hazard map, 155 of 229 Renton Hill lots (68%) touch a mapped coal mine hazard area and 55 (24%) touch a high one, mostly on Renton Ave S and Grant Ave S. Renton’s code defines high coal mine hazard as areas with abandoned, improperly sealed mine openings or workings shallow enough to risk collapse, and medium as deeper workings that may cause subsidence. For new development, a report is required within 200 feet of a medium hazard area and within 500 feet of a high one. Talbot Hill has mapped coal hazard as well, on 208 of its lots.

A mapped hazard is not a record of a problem at a particular house. It tells you which permit questions will come up. The Renton Hill guide has more on the neighborhood, and our Renton view homes guide shows why so many of these lots are worth the climb.

Renton Steep Slope Homes in Skyway-West Hill

Skyway is the largest of the three and the least steep. Only 77 of its 4,126 lots (under 2%) have a tenth or more at 40% or steeper on the city’s atlas, which extends across West Hill even though Renton’s rules do not apply there. Sixty-six of them are on the Lake Washington side, the Lakeridge and Bryn Mawr slope. The Campbell Hill and Skyway plateau lots barely register: 10 of 1,239 on the Campbell Hill side and none of 269 on the plateau.

King County’s own maps point to the same edge. Its 2016 potential landslide hazard map and the 50-foot buffer drawn around it reach 108 Skyway lots, on Rustic Rd S, Cornell Ave S, S Sunnycrest Rd, Lotus Pl S and Lakeridge Dr S. When we queried the county’s 2016 potential steep slope layer, it returned no mapped areas on West Hill’s residential lots, so for Skyway the landslide layer and a site study carry more weight than that map.

Skyway’s steep lots run larger, a median of 9,810 square feet against 7,440 for lots with no steep ground, and 45% carry a view rating. Our Skyway-West Hill guide covers the neighborhood, and Skyway ADU rules explains why King County’s critical areas rules override the Skyway zoning chapter when a slope is on the lot.

What the Codes Say About Renton Steep Slope Homes

Neither code stops anyone from owning or living in a hillside home. Both apply when someone applies for a permit to build, add on or grade.

In Earlington and on Renton Hill: RMC 4-3-050

• Geotechnical studies. A development permit on a site with sensitive or protected slopes, medium or higher landslide hazards, high erosion or seismic hazards, or medium or high coal mine hazards requires a study by a licensed geotechnical engineer or engineering geologist. The same applies when one of those hazards sits within 50 feet on a neighboring site.
• Protected slopes. Development is prohibited on them, with limited exceptions. The buffer table adds a 15-foot structure setback, and buffers are measured from the top, toe and sides of the slope. Non-exempt development on a site with a protected slope also requires a native growth protection area over the slope and its buffer.
• Very high landslide hazards. Development is not permitted, with a 50-foot buffer and a 15-foot setback beyond it.
• During construction. On sensitive slopes and medium or higher landslide areas, the code requires weekly site inspections directed by the geotechnical professional, at the applicant’s expense.
• Existing homes. Additions and alterations to an existing house or garage are exempt when they do not increase the footprint inside the critical area or its buffer and do not move closer to it.

In Skyway: KCC 21A.24

• Buffers. A buffer is required from every edge of a steep slope hazard area or landslide hazard area. Without a geological critical area report, the minimum is 50 feet. For single detached homes, the county may waive the report and reduce the buffer.
• Setbacks and vegetation. Structures sit at least ten feet back from the outer edge of the buffer under KCC 21A.24.200, and removing vegetation from the slope or buffer is prohibited unless it is part of an allowed alteration.
• Notice on title. Under KCC 21A.24.170, the owner of property with critical areas or buffers files a notice on title when a development proposal is submitted. It runs with the land, so a past owner’s permit can leave one on record for you to find.

Questions for Renton Steep Slope Homes Before You Offer

Washington’s seller disclosure form asks three questions that bear directly on a hillside lot: whether there has been any settling, slippage or sliding of the property or its improvements; whether any part of the property contains fill; and whether there are critical areas on the property. The same questions appear in the version of the form that takes effect on January 1, 2027. Read those answers closely, then:

1. Open the city’s map. In COR Maps, turn on Critical Areas, then Regulated Slopes, Landslide and Coalmine, and see where the colors fall on the lot. For Skyway, use King County’s iMap with its sensitive areas layers as well.
2. Note whether the steep ground is under the house or in the yard. A slope at the back fence and a slope under the foundation lead to very different permit conversations.
3. Ask for the paper trail. Ask the seller for any geotechnical report, permit file or recorded notice on title tied to the property.
4. Plan the project before you count on it. If you want to add a deck, an addition or a detached unit, ask the city or county what the slope and its buffer leave room for. Our Renton lot sizes guide shows how much land each neighborhood starts with.

For the other hazards on the same map, our guide to Renton flood zones covers the river and the valley floor below these hills.

Steep Slopes in the Highlands and Talbot Hill

The other neighborhoods we cover are flatter. In the Renton Highlands, 186 of 4,341 lots (4%) have a tenth or more at 40% or steeper, two-thirds of them built since 2000, and the high landslide hazard band follows the west edge above the Cedar River on Bronson Way NE, Grandey Way NE, Windsor Way NE and Monterey Dr NE. On Talbot Hill, 62 of 1,270 lots (5%) do, mostly on Lake Ave S, Talbot Rd S and Talbot Crest Dr S. North Renton has none.