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 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 HOW to build something.)
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.”
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, 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 SF 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.
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 30’, 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 30’ up from this imaginary line called “average grade,” the house could be 29’ tall in the front and 31’ 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. 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: you’re house can be 30’ tall.
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 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 not actually 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 blog about, 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 technically determine which property line is the front.
When you determine which side is the front and rear property line, you can determine the “lot depth.” This is the distance from the front property line to the rear property line. If you have an alley, the centerline of the alley is treated as the rear property line for this purpose. The rear setback (for a single family residence) is the lesser of 20% of the lot depth or 25’. This rear setback is measured from the center of the alley if you have one. Certain structures like garages, DADU’s, and other items are allowed within the rear setback areas (within certain limitations).
The front setback may be more straightforward and just simply be 20’. If your two adjacent neighbors are closer than 20’ to their front property line, then you can take the average of them. If the neighbor on the left is 16’, and the neighbor on the right is 18’, then your house’s front setback can be 17’. If your neighbor on the left is 16’ and your neighbor on the right is 22’, then you treat the neighbor on the right as 20’, and the 20’ and 16’ average out to 18’. The side setback is pretty simple since it is just 5’ unless it is a corner lot. In that case, the “street side” setback is 10’. Be careful to ensure you properly classify the front property line and street side property line on corner lots. In some cases, these are interchangeable, and in others they are not. It is not easy to clearly see which is the front and which is the street side (and again… no, your front door, or driveway, or address number, or your actual address do not decide which is considered your front property line).
With all of these setbacks, there are so many exceptions to the rules. Certain parts of your home can project into some setbacks like roof overhangs, bay windows, porches, decks, chimneys and some other features. There are limitations for the sizes and heights of these features, so please reach out for help in determining how to take advantage of these “loopholes.”
The next topic is lot coverage. In SF 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. 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 SF zoning classification, you are allowed to have 50% of the property count against your floor area ratio. So, with a 5000sf property, you are allowed to have an FAR of 2500sf of usable floor area. If you have an alley, you do not get to factor half of the alley into your calculation. This is different than the calculation for lot coverage discussed earlier. This is my current understanding of this new code that was introduced in 2020, BUT I have been told conflicting information by the building department on this alley topic. It does seem that when it matters, the city of Seattle doesn’t let you factor the alley area into you favor for FAR calculations.
I hope this post was informative and gives you a basic understanding of the SF5000 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 getting 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 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