On April 19, new rules went into effect for tree planting and protection requirements in single-family zones. The recently passed Mandatory Housing Affordability Ordinance 125791 made several important changes to tree protection requirements in the Seattle Municipal Code (SMC) 25.11, Tree Protection, and SMC 23.44, Single Family Zone. Those changes are:

1. SMC 25.11.040, Restrictions on Tree Removal, no longer includes an exemption from the exceptional tree designation or from requirements for tree removal on single-family lots less than 5,000 square feet. The exceptional tree rules now apply to all sizes of lots in single-family zones, including the residential small lot category. Trees can now be removed only under the same criteria that apply to lots greater than 5,000 square feet.
2. The residential small lot (RSL) zone is now a part of SMC 23.44, Residential, Single-Family.
3. The tree planting, retention, and protection requirements for single-family zones, formerly located in SMC 23.44.008.I, are now in a new section, SMC 23.44.020.  The “caliper inch” planting or retention requirement for lots zoned as single-family 5,000, 7,200, and 9,600 remain the same (SMC 23.44.020.A).  Planting or tree retention requirements for RSL lots is different. It is based on a point system and providing street trees is now required (SMC 23.44.020.B).  Unlike the other three single-family zones where street trees can be counted toward the planting or retention requirement, street trees are not counted toward the on-site requirement in RSL zones.

For more information about tree protection rules, see our Tree Protection Code webpage.

article copied from SDCI website  – New Rules for Single-Family Zones