Buying a lakefront lot on Lake Washington or Lake Sammamish: check what you can build before you close

If you are buying a lakefront lot, find out four things before you close: where the ordinary high water mark sits on the ground, how far back from it the city’s shoreline program lets you build, what the existing house and dock are legally allowed to be, and which approvals your plan needs. The lot size on the listing answers none of them. I am David Meade, an architect in Kirkland. My first feasibility check on a lake lot you are considering is free and very quick, usually about a day. If you want to go further, an in depth analysis is $1,500 and takes 2 to 3 weeks. I design the house and administer construction. I do not build.

This page is for a buyer with a project budget of $750,000 or more. I read the state laws on 29 October 2026 and the shoreline programs in the copies Ecology publishes. Confirm the live text with the city. I am not an attorney. My Lake Washington and Lake Sammamish pages compare each city’s line, and my shoreline exemption guide covers the exemption.

Why the listing does not tell you what you can build

Shoreline jurisdiction reaches 200 feet landward of the ordinary high water mark (RCW 90.58.030(2)(d)). A lot 140 feet deep from lake to street is entirely inside it, so every square foot answers to a shoreline program as well as zoning.

Where the water line is, and who decides

The state defines the ordinary high water mark by the bed and banks: where the water’s action is so common and usual that the soil and vegetation differ from the upland, as vegetation stood on June 1, 1971 (RCW 90.58.030(2)(c)). Ecology says its position varies from site to site and changes through time.

Kirkland’s map shows only the approximate extent of shorelands. For Lake Washington its program says the mark corresponds with a lake elevation of 18.5 feet on the NAVD 88 datum, and the extent on any lot comes from a field investigation and a survey that is the applicant’s sole responsibility (KZC 83.90(1)(b)(1)).

So ask for a boundary and topographic survey that plots the mark, house, deck, dock and bulkhead together. The setback, coverage strips and planting area all measure from the mark.

Buying a lakefront lot: how far back the city lets you build

I read two Lake Washington programs in the copies Ecology publishes: Kirkland’s Chapter 83 KZC (Ecology approval 21 September 2020; the copy is a city printout of 13 June 2023, current through Ordinance 4781 of 1 February 2022) and Mercer Island’s Chapter 19.13 MICC (effective 9 July 2020). Both lots below are hypothetical, made up to show the arithmetic.

Kirkland. In the Residential L (B), (C) and (D) environments the setback is a share of the average parcel depth, measured from the mark to the access edge (KZC 83.80(7)), with a floor and a cap. Take a hypothetical 140 foot average depth:

Environment (KZC 83.180)	Rule	Arithmetic	Depth left before yards
Residential L (B)	30 percent, floor 30 feet, cap 60	0.30 x 140 = 42 feet	140 minus 42 = 98 feet
Residential L (C)	25 percent, floor 30 feet, cap 60	0.25 x 140 = 35 feet	140 minus 35 = 105 feet
Residential L (D)	15 percent, floor 25 feet, cap 80	0.15 x 140 = 21, raised to 25 feet	140 minus 25 = 115 feet

The zone’s front and side yards come out of the remaining depth too, so these are upper bounds. Environments (A) and (E) to (J) use other rules, so ask which one the lot is in.

Lot coverage (structures, pavement and other impervious surface) is capped at 50 percent of the whole lot or of the part in shoreline jurisdiction (KZC 83.190(3)): on a hypothetical lot 70 feet wide and 140 deep, 70 x 140 = 9,800 square feet, so 4,900. Height is 30 feet above average building elevation, or the zone’s limit if lower (KZC 83.180, 83.190(4)). Mitigation from the program’s option chart can reduce the setback to no less than 25 feet in (B), (C) and (D), recorded with King County (KZC 83.380(2)(b)).

Mercer Island. Structures sit at least 25 feet from the mark, must meet the zone’s setbacks too, and stand at most 35 feet above average building elevation (Table C, MICC 19.13.050(A)). Hardscape and lot coverage are capped at 10 percent from 0 to 25 feet from the mark and 30 percent from 25 to 50 feet. Applying each percentage to its strip, a hypothetical lot with 75 feet of straight frontage gives:

Strip from the mark	Cap	Arithmetic	Allowed
0 to 25 feet	10 percent	75 x 25 = 1,875 sq ft, times 0.10	187.5 sq ft
25 to 50 feet	30 percent	1,875 sq ft, times 0.30	562.5 sq ft

Inside the 25 foot setback, a 20 foot vegetation area measured from the mark must carry native planting over 50 percent of it when new floor area, coverage and hardscape total 500 square feet, and over 75 percent at 1,000, counting additions from the prior five years (MICC 19.13.050(K)(4)). On 75 feet of frontage the strip is 75 x 20 = 1,500 square feet, so 750 or 1,125.

Lake Sammamish. The line comes from Issaquah, Sammamish, Redmond or Bellevue. Redmond’s adopted program, in the copy Ecology lists as January 2020, sets 35 feet, reducible to 20 if replanted with mostly native plants, with a City document recorded on the title saying the planting must stay (RZC 21.68.060(B)). A Redmond handout dated December 2023 says it can be reduced to 25 feet in some circumstances. The sources differ, so verify the live code with Redmond before relying on either figure. If the house you are buying used the reduction, the planting stays with the property.

What the old house, deck and dock are allowed to be

Each city writes its own test; the state default in WAC 173-27-080 applies only where a program has none. Ask:

• Was it legal when built? Kirkland lets what conformed when built continue and requires anything illegal when started to be corrected immediately (KZC 83.550(2), (3)).
• How much can I change? Mercer Island lets legally created structures within 25 feet of the mark be remodeled and completely replaced if the nonconformance does not grow (MICC 19.13.020(A), (B)).
• What goes if I rebuild? In Kirkland, an alteration to the primary structure costing over 50 percent of its replacement cost, or a new primary structure, means a nonconforming deck or patio in the setback and overwater decks must be removed or brought into conformance (KZC 83.550(5)(b)(5)).
• Is the lot itself buildable? A nonconforming lot may be developed if other rules allow it and the work meets the program (WAC 173-27-080(4)).

Height and the neighbors’ view

The state measures height from average grade level, the average of the ground elevations at the midpoint of every exterior wall (WAC 173-27-030(3), (9)). On a hypothetical house with wall midpoints at 52, 48, 44 and 40 feet, the average is (52 + 48 + 44 + 40) / 4 = 46, so the exemption’s 35 foot cap puts the highest point at elevation 46 + 35 = 81. Cities can set lower limits and measure differently: Kirkland uses average building elevation under Chapter 115 KZC (KZC 83.190(4)). A new or expanded building over 35 feet that would obstruct the view of a substantial number of residences adjoining the shoreline can be permitted only where the program does not prohibit it and overriding public interest will be served (RCW 90.58.320).

Which approvals your plan needs

Approval	When it comes up	Source
City shoreline program	Every development inside the 200 feet, exempt or not. A plan that misses a dimensional standard needs a variance, and after the city approves, Ecology decides within 30 days of submittal.	WAC 173-27-040(1)(b), 173-27-200(1)
Exemption from the substantial development permit	An owner, lessee or contract purchaser building a single family residence for own use, no taller than 35 feet above average grade, landward of the mark, meeting all other local rules. If any part is ineligible, the whole project needs the permit.	WAC 173-27-040(1)(d), (2)(g)
Hydraulic Project Approval	Work that uses, diverts, obstructs or changes the bed or flow of the water, such as a dock or bulkhead. Fish and Wildlife generally has 45 calendar days from a complete application.	RCW 77.55.011(11), 77.55.021(7)

What to ask the seller, the city and a surveyor

The seller. For an improved residential property the seller must deliver a completed disclosure statement within five business days after mutual acceptance unless otherwise agreed, and the form gives you three business days from delivery to rescind unless you agree otherwise in writing (RCW 64.06.020, the form in force until 1 January 2027; the revised form keeps these questions). It asks about zoning violations or nonconforming uses (1.I), encroachments (1.C), easements (1.E), shorelines or critical areas (7.D), and permits for additions or remodeling (4.C), on the seller’s actual knowledge. Vacant land has its own form (RCW 64.06.015). Then ask for permits for the house, deck, dock and bulkhead, and any recorded planting or setback agreement.

The city. Ask which shoreline environment the lot is in and what setback it sets. Seattle’s SDCI offers a Detailed Land Use Analysis with research, whose example is complex pre purchase due diligence, and a Rebuild Letter on zoning, violations and whether the structures can be rebuilt. Letters typically take 2 to 4 weeks, and SDCI says it does its best to meet a closing deadline if you say so. Mercer Island holds pre application meetings on Tuesdays by appointment, and Kirkland’s director may issue written interpretations of Chapter 83 (KZC 83.50).

The surveyor and title company. Ask the surveyor to show the mark, improvements and easements on one drawing, and whether a record of survey is on file with the county auditor (RCW 58.09.040).

How the feasibility check works with me

A feasibility study tests a lot against the city’s adopted rules before you commit money to design. My free first check is very quick, usually about a day: you send me the address and what you are considering, and I reply to you personally. The in depth analysis is $1,500, takes 2 to 3 weeks and goes further.

Step	Time or cost	What it is
Free first feasibility check	Free, usually about a day	You send the address and what you are considering.
In depth analysis, optional	$1,500, 2 to 3 weeks	Goes further than the first check.
Design to permit submission	Typically 2 to 4 months	Covered by my fixed fee.
Permit	Seattle: remodel about 2 to 3 months, new house 6 to 10	Other cities set their own.

What it costs

Item	Planning figure	Note
Design and permit fee	Fixed fee, about $10,000 to $200,000	Set by project budget and location, not a percentage.
In depth analysis	$1,500	Optional, 2 to 3 weeks.

Planning ranges from Piper Cole, not quotes. My smallest project is $750,000. City fees are set by the city and construction is priced by a builder.

I have been an architect since 1996, an AIA member since 1992 and an NCARB member since 1996, and the Carr residence was featured in Above The Lake and Lux magazines.

Questions

Can I build a house on a lakefront lot in Washington?

Often, but the lot decides. Inside 200 feet of the ordinary high water mark the city’s shoreline master program and its zoning both apply, and the program sets the setback, coverage, height and planting rules (RCW 90.58.030(2)(d)). Kirkland’s chapter, for example, applies as an overlay in addition to zoning, and the rule that protects the shoreline more prevails (KZC 83.40). A feasibility study tests a lot against those adopted rules before you commit to design, and my first one is free and usually takes about a day. I design the house and administer construction. I do not build.

How far back from the water can I build on Lake Washington?

It depends on the city and the lot’s shoreline environment. Mercer Island sets structures at least 25 feet from the ordinary high water mark, and the zone’s setbacks also apply (MICC 19.13.050, Table C). Kirkland sets a share of the average parcel depth: on a hypothetical 140 foot deep lot, 30 percent in Residential L (B) is 42 feet, 25 percent in (C) is 35 feet, and 15 percent in (D) is 21 feet, raised to the 25 foot floor (KZC 83.180). Read from Ecology’s copies of each program on 29 October 2026. Confirm with the city.

What is the ordinary high water mark and why does a lake buyer need it surveyed?

It is the mark on the ground, found by vegetation and soil along the bed and banks, where the water’s action is so common and usual that it separates the lake from the upland (RCW 90.58.030(2)(c)). The setback, coverage strips and planting areas all measure from it. Kirkland’s program says the mark on Lake Washington corresponds to a lake elevation of 18.5 feet on the NAVD 88 datum, but that the exact extent on any lot comes from a field investigation and a survey that is the applicant’s responsibility (KZC 83.90). A survey that shows only property lines does not give you the setback.

Do I need a shoreline permit to build my own house on a lake lot?

Not the substantial development permit, if you are an owner, lessee or contract purchaser building a single family residence for your own or your family’s use, no taller than 35 feet above average grade level, landward of the ordinary high water mark, and the house meets every other local requirement (WAC 173-27-040(2)(g)). You still need the city’s approval, and the house must meet the shoreline program’s setback, planting and height rules. A plan that misses a dimensional standard can only be authorized by a variance, which Ecology also reviews (WAC 173-27-040(1)(b), 173-27-200).

Does a Hydraulic Project Approval apply when I buy a lake lot?

Only if you plan work that will use, divert, obstruct or change the natural flow or bed of the water, such as building or replacing a dock or bulkhead (RCW 77.55.011(11)). The application goes to the Department of Fish and Wildlife with complete plans for any work inside the ordinary high water line, and the department generally has 45 calendar days from a complete application (RCW 77.55.021). Ask the seller for the approvals behind any dock or bulkhead that comes with the lot.

What happens to an existing house that sits inside the shoreline setback?

Usually a legally built house can stay and be maintained, and each city sets how much you may change it. Mercer Island lets structures within 25 feet of the mark be remodeled and completely replaced if the nonconformance does not grow (MICC 19.13.020). Kirkland requires a nonconforming deck or patio in the setback to be removed or brought into conformance when an alteration to the primary structure exceeds 50 percent of its replacement cost or a new primary structure is built (KZC 83.550(5)(b)(5)). My Lake Washington and Lake Sammamish pages compare the cities.

Can I keep or replace the dock that comes with the lot?

Check three things before you close. First, whether the dock was permitted, because anything illegal when started must be brought into conformance in Kirkland (KZC 83.550(3)). Second, what a replacement needs: a freshwater replacement dock of equal or smaller size is exempt from the substantial development permit up to $28,000 in a city with an updated program, and other docks up to $13,900 (WAC 173-27-040(2)(h), WSR 23-13-012), the city’s program still applies, and in water work needs a Hydraulic Project Approval. Third, which land it sits on, since a dock on state owned shorelands is allowed without charge only where the area is not subject to prior rights (RCW 79.105.430).

What does your feasibility check cost and how long does it take?

The first basic feasibility check is free and very quick, usually about a day. An in depth analysis is $1,500 and takes 2 to 3 weeks. If you then hire me, I quote one fixed fee for design and permit, about $10,000 to $200,000, set by the project budget and location. My smallest project is $750,000. Design to permit submission typically takes 2 to 4 months. Construction is priced separately by a builder, because I administer construction and do not build.