If you’re confused and not sure where to start for planning a small remodel, or even a large addition, or a totally new construction project for your house in Seattle and other areas, you are not a stupid, total idiot:) Even for a seasoned veteran architect in Seattle who specializes in residential architecture, the codes, rules, regulations, policies, etc are very confusing to say the least. If anyone is a stupid idiot, it’s the ones who wrote the codes in such difficult language:) I am here to help, and this post is your guide to help you navigate the thick bureaucracy. (It is also worth noting there is a major difference between the “building code” and “land use code”. This post only dives into the “land use code” to help you understand WHAT/WHERE you are allowed to build on your property and not the “building code” which gets into the specifics of HOW to build something.)
All of the housing rules in Seattle got significantly changed in 2025, so be sure to educate yourself by reviewing the paragraphs below.
The land use code classification that is applicable to most single family homes in Seattle is known as NR3 (formerly named SF5000, SF7200 renamed to NR2, and SF9600 renamed to NR1 for larger lots). The “SF” meant: Single Family. The 5000 meant the property is more or less 5000 square feet. The rules are pretty much the same for all these zones except for the bigger lot sizes. The new naming convention of “NR” means “Neighborhood Residential.”
OVERVIEW
The most basic, common concepts in NR zoning are yard setbacks, maximum percentage of lot coverage, floor area ratio, and height limit. Some of the other nuances in the codes are the exceptions to all these rules, tree requirements, and parking requirements. Some projects may also involve various other codes for garages, ADU’s (accessory dwelling units), DADU’s (detached accessory dwelling units), existing nonconforming uses (projects with non-compliant stuff that is “grandfathered in” since it was built before the codes existed), allowable uses (like using your house as a hotel), and ECA’s (properties within environmental critical areas such as steep slopes, shorelines, etc).
In Seattle, I have dealt with zero properties that are straightforward. There is always something weird about each lot such as a part of the existing house that was built too close to the property line, a part of the lot that is considered an ECA because it is too steep, something a previous owner built without a permit, difficulty in determining which side is technically considered the “front,” or a tree the city won’t allow you to remove (which causes the lot to be less than ideal to build on). Because of these anomalies that always seem to pop up, no two projects have ever been the same (and I do about 100 of them each year). The rest of this blog post will dig into each topic separately to attempt to give you some insight into each of the major codes for NR zoning. Although this will give you a basic understanding, please reach out for confirmation since this stuff gets really complicated and must be vetted (we are not liable for your use of the information herein). Also, just because the code says something in “black and white,” the building department may actually interpret it to mean something completely different. And, they are not always correct in what they tell you. I commonly argue with them to show them what the rules actually mean (and not let them bestow their “opinions” on me). There’s usually some compromise, but I’ve never lost an argument with the building department.
HEIGHT LIMIT
Let’s start with the height limit since it’s one of the easiest to understand. The maximum height of a house is permitted to be 32’, and this is measured from the “average ground height” to the top of the highest wall. A sloped roof of a certain angle (4:12) can extend an additional 5’ higher. The average ground height is determined by measuring the height of the ground at the middle of each exterior wall and taking the average of those. For example, if the ground sloped down so the front was 2 feet higher than the ground at the back of the house, and the sides were each 1’ higher than the back of the house, then (2’+1’+1’+0’)/4 = 1’. So in other words, the average ground level is 1’ higher than the back, and 1’ lower than the front. If you measure 32’ up from this imaginary line called “average grade,” the house could be 31’ tall in the front and 33’ tall in the back. The sloped roof can go another 5’ higher, and you’re also allowed to have chimneys, vents, skylights, and dormers of limited sizes within this 5’ bonus area (and sometimes higher). There’s also exceptions for green roofs and certain features of roof decks. As you can see, it’s not as simple as just saying: your house can be 32’ tall.
SETBACKS (YARDS)
Next, let’s review setbacks. A setback is the distance from a property line where you are not allowed to build (certain things). To be able to determine setbacks from each property line, you first need to know where the property lines are. No, your fence, sidewalk, curb, rockery, driveway, or that thing the old guy in the neighborhood showed you once is likely NOT THE PROPERTY LINE. Sorry. It’s probably not. A property line must be determined by a licensed surveyor by taking precise measurements with very technical instruments. Then, they put a surveyor’s pin to mark the location of the property corner (and sometimes these are intentionally placed NOT on the corner of the property as you may expect).
Once you know WHERE the property lines are, THEN you can determine which is considered the front, side, and rear property lines. This may seem straightforward, but sometimes it is not. This is too complicated to write about here, so let’s talk about this topic on a case-by-case basis. Feel free to reach out since your front door, address location, your actual street address, or your driveway do not actually determine which property line is the front.
In NR zoning, the front setback is 15’, but if you have 3 or more dwelling units, you can reduce it to only 10’. The rear setback for NR zoning is also based on the number of units you have on the lot. If you have 1 or 2 dwellings, you need to provide a 15’ setback from the rear property line, and if you have 3 or more dwellings, you only need to provide a 10’ rear setback. If you have an alley, you are allowed to build directly up to the rear property line (regardless of how many units you have). The side setback is easy in NR zoning. It’s 5’. At least that one is easy! There are also a lot of exceptions to the rules for various parts of a structure, so be sure to consult with us for specific clarification.
LOT COVERAGE
The next topic is lot coverage. In NR zoning, you are allowed to cover 35% of your lot with structures. If the lot is less than 5000SF, then you are allowed to cover 15% of the lot plus 1000SF. If your lot abuts an alley, you are allowed to factor 1/2 of the area of the alley into your calculation for the size of the lot. If you have 2 or more dwelling units on the lot, then the maximum lot coverage calculation increases to 50% of the lot area. Lot coverage is pretty easy to calculate, but the exceptions to the rule do get tricky. For example, decks lower than 36”, solar panels, fences, and the first 36” of roof overhangs do not count against lot coverage, and there are some additional nuances to what counts and what does not.
FLOOR AREA RATIO
Floor Area Ratio (known as FAR) is the last topic we will discuss here. This is a measure of the usable floor space inside a building. So, if you have a 1000sf first floor and 1000sf second floor, then you have 2000sf of floor area used up…sort of. The stair doesn’t count twice, some basements don’t count, certain porches don’t count, and there’s also other exceptions that don’t count against you. In the NR zoning classification, there is a sliding scale for the amount of floor area you are allowed to have, and it is based on the number of dwelling units the property has. The calculation is a ratio between the number of dwelling units and the size of the property. With less than 1 unit per 4000sf of lot area, you are allowed a floor area ratio of 60% of the lot size. For example, if you have 1 house on a 3000sf lot, 60% of 3000sf is 1800sf of maximum floor area allowed, BUT the minimum allowed for any lot is always 2500sf (even if the calculation is less). Also, if you are in an RSL zone, the calculation is 75% of the lot area. If your NR lot is slightly more dense and has between 1 unit per 4000sf and 1 unit per 2201sf, then the FAR increases to 80% of the lot area. If your NR lot is even more dense and has between 1 unit per 2200sf and 1 unit per 1601sf, then the FAR increases to 100% of the lot area. Finally, if your lot is denser than 1 unit per 1600sf, the your FAR increases to 120% of the lot area. For example, if you have 4 units on a 5000sf lot, that ratio is 1 unit per 1250sf, so you could use the FAR of 120%. That means your 5000sf lot can have a maximum of 6000sf of floor area. If you have an alley, you do not get to factor half of the alley into your calculation like you would for the lot coverage calculation discussed earlier. This is my current understanding of this new code that was introduced in 2025.
CONCLUSION
I hope this post was informative and gives you a basic understanding of the NR (SF) zoning classification in Seattle to help you determine approximately what you’re allowed to do with your property. I recommend that you do not discuss specifics of your project with the building department unless you first run it by an architect that is VERY experienced in the zoning classification in your area since you may “shoot yourself in the foot” by saying the wrong thing and get locked into adverse interpretations. We are here to help you figure out the specifics since the rules are tricky and there’s a lot of exceptions to the rule that can be used in your favor. As a disclaimer, the topics covered here are generalizations that could easily get misinterpreted, and you should consult with an expert architect for specific interpretations.
If you’d like to learn more about our design process, visit www.josharch.com/process, and if you’d like to get us started on your project with a feasibility report, please visit www.josharch.com/help