Buying a house to remodel in Seattle or on the Eastside: check what you can change before you close

If you are buying a house to remodel, find out four things before your inspection or feasibility period ends: what the city’s rules let you change and keep, what the permit history says about the work already done, whether a critical area, shoreline or tree rule sits on the lot, and what the remodel costs against what you will pay for the house. The listing answers none of them. That is remodel feasibility before you buy, and it is the question behind “what can I remodel before I buy?” I am David Meade, an architect. My first feasibility check on a house you are considering is free and very quick, usually about a day. An in depth analysis is $1,500 and takes 2 to 3 weeks. I design the remodel and administer construction. I do not build.

This page is for a buyer with a project budget of $750,000 or more who is looking at an existing house in Seattle or on the Eastside. I read the sources named below on 31 October 2026. Confirm the live text with the city. I am not an attorney. If you plan to demolish, read my teardown feasibility page. A lake lot has its own shoreline rules, on my lakefront lot page.

Why the listing does not tell you what you can remodel

A listing gives you bedrooms, square feet and a year built. It does not say whether the house sits inside a yard that today’s code would not allow, whether the basement and addition were permitted and finaled, or whether the lot carries a critical area. A house built under an older code can be legal and still short of today’s yards, height or coverage. Cities call that legal nonconforming, and each decides how much you may change before the protection ends.

What each city lets you change and keep

These tests matter only if the house is nonconforming, and the measure differs by city. The same remodel can be fine in one and cross a line in another.

City	What it counts	Source
Seattle	A published copy shows no cost or wall percentage. A nonconforming structure may be maintained, renovated, repaired or structurally altered, but not expanded in a way that increases the nonconformity.	SMC 23.42.112 (A), published copy
Mercer Island	Structurally altering more than 40 percent of the length of the existing exterior walls ends the nonconforming status, and the city counts walls that are completely removed. A published copy adds a five-year cumulative window and says an interior remodel keeps the status at any cost if nothing outside changes.	MICC 19.01.050 (C), (D)(1)(b); city interpretations 04-01 and 07-02
Kirkland	A published copy shows that a roof or exterior wall that misses the height or yard standards must conform if you structurally alter it. For other nonconformances, work above 50 percent of replacement cost in a consecutive 12 months means correcting them.	KZC 162.35 (7), (13), published copy
Issaquah	Remodel cost under 75 percent of the latest King County tax assessed improvement value gets a Level 1 review. At 75 percent or more, the site is reviewed as new development. Either way the change must reduce the nonconformity as far as practical and feasible.	IMC 18.214.070 (B), (C), Ord. 3013

Sources: the Seattle and Kirkland rows rest on published copies of those codes, because the city code sites refused my request and I did not work around that, so the city’s code controls. The Mercer Island 40 percent rule comes from the city’s 2004 and 2007 interpretations, and the rest of that row from a published copy. Issaquah is from Ordinance 3013 as adopted, effective 1 June 2023. Other cities are in my comparison guide.

Mercer Island counts walls. The city’s 2007 interpretation says the alterations that count toward the 40 percent are lengths of exterior walls that are completely removed. A published copy of the code divides the length of existing exterior walls to be structurally altered by the length of all existing exterior walls, treats a wall as completely demolished when any portion is removed so that no structural elements remain, and counts a bay window bump-out as its own wall plane. The city’s definition says replacing cladding or glazing in existing openings is not structural alteration (MICC 19.16.010). The same copy looks back five years, so ask the seller about structural work in that time.

Issaquah makes the owner prove it. The burden of showing a structure is legally nonconforming sits on its owner, and if the owner cannot show it the city may require compliance (IMC 18.214.030). A sale does not end the right to continue (IMC 18.214.110), but if the structure is demolished, anything new must conform (IMC 18.214.050).

Seattle’s building code is a second test. The residential code lets the building official treat a remodel that substantially extends the useful physical or economic life of the building or a significant portion of it as a substantial alteration. That brings current rules for escape openings, egress, smoke and carbon monoxide alarms and dwelling unit separation, plus seismic provisions, and the official may require testing of existing materials at the owner’s expense when evidence of structural strength is insufficient (SRC R107.5.1 to R107.5.1.2, 2021 edition; SDCI says the 2024 Seattle codes come no sooner than May 2027). There is no number, so ask SDCI early how your scope reads.

What the permit history can tell you

• Seattle. SDCI says the Seattle Services Portal shows permit activity from 2005 to the present but not historical microfilm permits. Its Permit and Property Records library covers permits and inspections from 2005 and is uploading scanned older permits from about 1894 to 2004. Plans for issued permits come on a written request with the permit number and project address.
• Mercer Island. The city’s map portal holds historic building permits, sewer as-builts and geotechnical reports for a parcel.
• Bellevue. Development Services Permit Records manages building permits, plans and land use files, and requests go through the city’s online portal.

Approved plans show what the city approved, not what was built later, so compare them with the house. A finished basement, bathroom or deck that appears nowhere in the records is a question for the seller. Washington’s seller disclosure statement for improved residential property asks whether there have been conversions, additions or remodeling and whether all permits and final inspections were obtained (item 4.C), and about zoning violations or nonconforming uses (1.I), shorelines or critical areas (7.D) and encroachments (1.C). The seller answers from actual knowledge, and the form is not a warranty. It is due within five business days after mutual acceptance unless agreed otherwise, and you have 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).

Legalizing work costs money. In Seattle, SDCI’s 2026 Fee Subtitle adds a special investigation fee on top of the permit fee where an investigation is made for an action that required approval. It is a multiple of the $292 base fee that rises with the value of the work: 5 x $292 = $1,460 for work of $50,001 to $100,000, and 50 x $292 = $14,600 for $500,001 to $5,000,000. The Director may instead charge the hourly rate. The fee does not excuse code compliance and is not refundable (SMC 22.900B.010, 22.900B.020, Table B-2). I found no comparable table for the Eastside cities, so ask the city.

Buying a fixer upper on the Eastside: a worked example from Issaquah

Issaquah’s test is one number you can look up before you close. Take a hypothetical 2,200 square foot house that is legally nonconforming, for instance built inside today’s side yard. Say the latest King County tax assessed improvement value is $600,000. That figure is made up; the real one is on the Assessor’s record for the parcel. The line is 0.75 x $600,000 = $450,000. My planning range for whole house renovation is $300 to $550 per square foot, and I apply it to the partial remodel too, for illustration.

Scenario	Cost at the planning range	Against the $450,000 line	Review path
Whole house, low end	2,200 x $300 = $660,000	$660,000 to $450,000 = $210,000 over	New development
Whole house, high end	2,200 x $550 = $1,210,000	$1,210,000 to $450,000 = $760,000 over	New development
1,000 sq ft, low end	1,000 x $300 = $300,000	$450,000 to $300,000 = $150,000 under	Level 1
1,000 sq ft, high end	1,000 x $550 = $550,000	$550,000 to $450,000 = $100,000 over	New development

To keep the whole house under 75 percent, the improvement value would have to exceed $660,000 / 0.75 = $880,000 at the low end and $1,210,000 / 0.75 = $1,613,333 at the high end. For my smallest project budget, $750,000, it is $750,000 / 0.75 = $1,000,000. In this example the whole house lands in new development review, so look up the real figure for the parcel you are considering. On either path the change must reduce the nonconformity as far as practical and feasible, and a detached single-family structure may be modified or expanded as long as the nonconforming portion is not increased (IMC 18.214.070(C), 18.214.100).

What I could not confirm: the ordinance does not say how the city counts remodel cost, so ask Issaquah. I could not open the county page that lists the Assessor’s report fields, so check that the report shows an improvement value apart from land. The same buyer in Mercer Island would count walls, and in Kirkland would ask which walls and roofs sit in a yard. The wider choice is in my remodel or tear down guide.

Critical areas, shoreline and trees

The seller’s form asks about shorelines, wetlands, floodplains and critical areas (7.D), but the city’s answer decides what you can build. Issaquah shows how specific that gets. Near a wetland or stream buffer, a nonconforming building may expand outside the buffers, add upper stories, and build over existing impervious surface inside the buffer if it does not move closer to the water, with buffer enhancement when the expansion is over 500 square feet (IMC 18.214.070(C)(4)). Anything else needs a variance. Seattle’s rules are in my critical areas guide. On a lake lot the shoreline program sets the line from the water; the lakefront lot page covers it.

Trees can decide where an addition goes. Seattle’s rules are in motion: SDCI’s tip sheet on tree requirements for development warns that interim regulations effective July 2025 and pending changes mean it may not reflect current requirements. Read my tree ordinance guide and ask the city about the trees on the lot.

Budget reality for a house you are buying to remodel

The only construction range I use for a whole house renovation is $300 to $550 per square foot, a planning range and not a quote, on top of the purchase price.

House size	At $300 per sq ft	At $550 per sq ft
2,000 sq ft	2,000 x $300 = $600,000	2,000 x $550 = $1,100,000
2,500 sq ft	2,500 x $300 = $750,000	2,500 x $550 = $1,375,000
3,000 sq ft	3,000 x $300 = $900,000	3,000 x $550 = $1,650,000

Turned around, $750,000 covers about 1,364 to 2,500 square feet ($750,000 / $550 = 1,364; $750,000 / $300 = 2,500). The architect’s fee is separate: one fixed fee for design and permit, about $10,000 to $200,000, set by the project budget and location. City fees are set by the city, and a builder prices construction. I give no financing advice, so ask your lender how it treats a renovation. My million dollar remodel guide goes deeper.

Questions to ask before the inspection period ends

• The seller. Which additions and remodels were done, by whom, under which permit numbers, and were they finaled? What structural work in the last five years?
• The city. Is the house legally nonconforming, and how? In Seattle, SDCI offers a rebuild letter on zoning, code violations, the legal use and whether the structures can be rebuilt, which a lender may ask for, and a detailed land use analysis for complex due diligence. Opinion letters typically take 2 to 4 weeks, and SDCI says it does its best if you need a letter quickly because of a closing.
• The records. Do the approved plans match what is standing? If not, what would legalizing the difference involve?
• The structure. Which walls carry load? See when a remodel needs a structural engineer.
• The drawings. Who measures the house, and who pays? My existing conditions page lists what each city asks you to show.
• Your dates. When does each contingency end? Ask your agent or attorney.

How the feasibility check works with me, and what it costs

A feasibility check asks, before you commit money to design, whether a house and lot can do what you want under the city’s adopted rules. 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 goes further. If you then hire me, I design the remodel and administer construction. I do not build.

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 and permit fee	Fixed fee, about $10,000 to $200,000	Set by project budget and location, not a percentage.
Design to permit submission	Typically 2 to 4 months	Time from starting design to filing the permit application.

Planning ranges from Piper Cole, not quotes. 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.

Questions

What should I check before buying a house to remodel?

Four things. First, whether the house is legally nonconforming and how much the city lets you change before that protection ends. Second, the permit history against the house as it stands. Third, critical areas, shoreline and trees on the lot. Fourth, the cost of the remodel against the purchase price. Each city counts differently: Issaquah compares remodel cost with 75 percent of the assessed improvement value (IMC 18.214.070), Mercer Island limits structural alteration to 40 percent of exterior wall length (MICC 19.01.050), and Seattle bars expanding the nonconformity (SMC 23.42.112). Confirm each with the city. My first feasibility check is free and usually takes about a day.

What can I remodel before I buy, and what can I not?

You can remodel what the city’s rules allow for that house, and the house decides it. A conforming house has no grandfathered status to lose. A legally nonconforming house keeps its status only while the work stays inside the city’s limit, and a change may not make the nonconformity worse. A published copy of Mercer Island’s code lets an interior remodel proceed at any cost if nothing outside changes (MICC 19.01.050(C)), and a published copy of Seattle’s code allows renovation and structural alteration without expanding the nonconformity (SMC 23.42.112). Only the city can confirm which situation your house is in.

How do I find out whether a house has unpermitted work?

Pull the city’s permit records for the address and compare them with the house. In Seattle, SDCI’s Services Portal shows permit activity from 2005 to the present, and its Permit and Property Records library is uploading scanned permits from about 1894 to 2004. Mercer Island’s map portal holds historic permits and sewer as-builts, and Bellevue’s Development Services Permit Records holds permits and plans. Then read the seller’s disclosure statement, which asks whether all building permits and final inspections were obtained for conversions, additions or remodeling (RCW 64.06.020, item 4.C). The seller answers from actual knowledge, so the records matter.

What does it cost to legalize unpermitted work?

It depends on the city, the work and what the inspector finds, so I give no total. In Seattle, SDCI’s 2026 Fee Subtitle adds a special investigation fee on top of the permit fee: 5 x the $292 base fee for work of $50,001 to $100,000, and 50 x for $500,001 to $5,000,000 (SMC 22.900B.020, Table B-2). Paying it does not excuse code compliance. I found no comparable table for the Eastside cities, so ask the city.

Does buying a fixer upper on the Eastside work differently from Seattle?

Yes, because each city writes its own test. Seattle sets no cost or wall percentage. Mercer Island counts exterior wall length, Kirkland asks which walls and roofs you alter, and Issaquah uses assessed improvement value, with 75 percent as the line (MICC 19.01.050, KZC 162.35, IMC 18.214.070). Confirm with the city. My comparison guide covers more cities. Check the city before you plan around any of them.

How much does it cost to remodel a whole house?

My planning range for whole house renovation is $300 to $550 per square foot, which is a planning range and not a quote. A 2,500 square foot house comes to $750,000 at the low end and $1,375,000 at the high end. That is construction, on top of what you pay for the house. My fee for design and permit is fixed, about $10,000 to $200,000, set by the project budget and location. My smallest project is $750,000.

Do I need an architect to remodel a house I buy?

Washington law does not require an architect to design a residential building of up to four dwelling units (RCW 18.08.410(5)). Whether to hire one is your call. Where the house is nonconforming or you want to change structure, an architect can read the city’s rules against your plans. I do not build.

Should I have the house measured or surveyed before I close?

It depends on the city and on how close the plan sits to a limit. A survey fixes the lot corners and ground elevations that setbacks and height are measured from, and measured drawings fix the house. Cities ask for them at different points; my existing conditions page lists what six of them say. Check your purchase agreement for what access you have before closing.

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. 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.