The Sammamish tree removal rules cap how many significant trees you may take off a lot over a ten year period, and the cap is set by lot size rather than by what you intend to build. Add the landslide buffer on sloped ground and the hardscape ceiling on every residential zone, and a Plateau lot often allows less than its acreage suggests.

This is the part of a Sammamish purchase that buyers tend to discover after closing. A property looks like room for a larger footprint, a shop, a sport court or a second structure, and then the code narrows it. None of it is hidden. It is published by the city and it is readable before you write an offer.

Here is what governs a Sammamish lot, in the order it will affect you.

What the Sammamish Tree Removal Rules Actually Say

The city's Permit Center tree removal page publishes the Sammamish tree removal rules directly, and the operative code section is SMC 21.03.060. Two definitions do most of the work.

The first is the significant tree. A coniferous tree is significant at 8 inches diameter at breast height or larger. A deciduous tree is significant at 12 inches or larger. Below those thresholds a tree is not counted in your allowance. At or above them it is, and a Tree Removal Permit is required to remove it. A tree standing in the street right of way is a separate matter and takes a Type B Right of Way permit rather than a tree permit.

The second is the allowance itself, and it is the one people misread. It is not a single number. It is three limits applied simultaneously, and the city states plainly that the number of significant trees allowed for removal is limited to whichever of the three columns is lowest.

How Many Trees You Can Remove, by Lot Size

The schedule reads as percentage over ten years, then annual number, then cumulative number over ten years.

• Less than 1/4 acre. 50 percent over ten years, 2 per year, 6 cumulative over ten years
• 1/4 to 1/2 acre. 40 percent over ten years, 4 per year, 12 cumulative over ten years
• 1/2 to 1 acre. 30 percent over ten years, 6 per year, 18 cumulative over ten years
• 1 to 2 acres. 20 percent over ten years, 8 per year, 24 cumulative over ten years
• More than 2 acres. 10 percent over ten years, 10 per year, 30 cumulative over ten years

Work an example on a half acre lot in the 30 percent row. If the parcel holds 20 significant trees, the percentage column allows 6, the annual column allows 6 in a given year and the ten year cumulative column allows 18. The lowest applicable figure controls, and the ten year window matters as much as the number. A previous owner who took trees down recently has already spent part of the allowance you would inherit.

Larger parcels are where the arithmetic surprises people. The percentage tightens as lot size grows, so acreage buys you fewer removals per tree standing, not more. Our guide to Sammamish horse properties and acreage covers the rest of what changes when a parcel gets large.

The Sequencing Rule That Changes Your Whole Timeline

One line in the code reorders every plan that involves construction. Under SMC 21.03.070.I.2.b, on sites where development is proposed or anticipated, removal of any trees shall not take place until a permit for construction has been issued.

Read that carefully, because it runs against the instinct. You cannot clear the lot and then design around the space you opened. The design comes first, the construction permit comes first, and the trees come down after. That sequence lengthens the front end of a rebuild or a major addition, and it means the trees standing on the lot are a design input rather than an obstacle you remove early.

It also means a lot marketed as ready to build is worth a question. Our guide to teardowns and custom rebuilds in Sammamish walks through the rebuild decision itself, and our builder guide covers what to ask a builder about their own permitting assumptions.

Steep Slopes and the 50 Foot Landslide Buffer

Sammamish sits on a plateau with real grade changes at its edges, which puts geologically hazardous areas on a meaningful share of parcels. The city groups landslide hazard areas, steep slopes and erosion hazard areas together in that category.

The number to know is 50 feet. In a landslide hazard area, the city requires a minimum buffer of 50 feet established from the top and the toe of the slope, to protect structures that could be affected by a landslide event. Both ends, not one. A slope crossing the middle of a parcel can therefore consume buffer in two directions.

The buffer is not fixed in either direction. The city may extend it to mitigate a landslide or erosion hazard or to protect public health and safety. It may also be reduced or removed based on a critical areas study, if the city determines the critical area will still be adequately protected. Which of those applies to a given parcel is a question for a qualified geotechnical professional, and the city notes that field verification and site specific assessment are what delineate these areas and their buffers in the first place. A published hazard map is a starting point, not an answer.

The Other Critical Areas on the List

Geologic hazards are one of six regulated categories. Sammamish also regulates critical aquifer recharge areas, frequently flooded areas, habitat conservation areas and migration corridors, streams, and wetlands.

Two things follow from that list. First, a single parcel can carry more than one designation, and the constraints stack rather than cancel. Second, buffers for streams and wetlands are set by classification, which is determined on the ground by a qualified professional rather than read off a map. If a lot has water on it or near it, budget time in your contingency period for someone to look at it.

This is also where the utilities question tends to surface on the less developed parts of the Plateau. Our guide to buying a Sammamish home with a septic system or well covers the drainfield and water side of the same diligence.

How Much of the Lot You Can Cover

Trees and slopes limit what you can clear. Hardscape limits govern what you can then cover. The city publishes maximum hardscape by residential zone under SMC 21.04.030.C, with surface water management at SMC 21.03.050 layered on top.

• R-1. 30 percent maximum hardscape
• R-4. 40 percent
• R-6. 50 percent
• R-8. 75 percent
• R-12 and R-18. 85 percent

Hardscape here is broader than the house. The city counts buildings, driveways, walkways, decks and any other area not designed for the growth of vegetation, and it specifically counts gravel, pavers and similar quasi hardened surfaces. The calculation is simply hardscape divided by lot size. A long driveway on a large-lot R-1 parcel can absorb more of a 30 percent ceiling than owners expect, before a shop or a sport court is drawn at all. Public Works stormwater regulations apply in addition to these percentages, so meeting the zone ceiling is not automatically the end of the analysis.

If your interest is what a renovation returns rather than what it costs to build, our look at which remodeling projects return value in Sammamish is the companion piece to this one.

Middle Housing Overlays and What They Change

Sammamish has mapped middle housing overlays, designated MHO-1, MHO-2 and MHO-3, across the R-1 through R-8 zoning districts. The city's own framing is that middle housing is not mandatory but is encouraged, through increased density allowances and tiered floor area ratios. Development under the overlays is subject to the city's Mandatory Affordable Housing Program, with units under 1,500 square feet exempt from the affordable housing calculation.

For a buyer, the practical read is narrow and worth keeping narrow. An overlay may expand what a parcel could hold. It does not suspend the tree allowance, the landslide buffer or the critical areas review, and the overlay assignment is parcel specific. Confirm the overlay for an address with the Permit Center rather than assuming from the zone.

What the Sammamish Tree Removal Rules Mean for Your Offer

Turn all of it into diligence you can actually run inside a contingency period.

• Count the significant trees before you plan around them. Walk the lot with the DBH thresholds in mind, conifer at 8 inches and deciduous at 12
• Ask what has already been removed. The allowance runs on a ten year window, and it does not reset at closing
• Check the parcel for critical area designations early, since geologic hazards, streams and wetlands each bring their own study requirement
• Look for grade at the property edges, then measure 50 feet in from the top and the toe before you draw anything
• Run the hardscape math on your zone, including driveway, walkways, decks and gravel, not only the house footprint
• If construction is the plan, build the permit sequence into your timeline, because no trees come down before the construction permit issues
• Take site specific questions to the people who answer them, which means the Sammamish Permit Center, a certified arborist and a qualified geotechnical professional

A lot with slope, trees and a stream is not a bad lot. It is a lot with a longer diligence list, and the buyers who run that list before the offer are the ones who do not find out in month three. Views on the Plateau often come from exactly the grade that carries a buffer, which our guide to Sammamish view homes gets into.

Frequently Asked Questions About Sammamish Tree Removal Rules