Seattle whole-house remodel and addition: the project workflow

A whole-house remodel with a single-story addition on a Seattle bungalow or rambler is a 12 to 20 month project that pulls you through SDCI's Addition/Alteration permit track, an interior gut, a kitchen that drives most of the design, structural wall removals to open the plan, and (almost always) a substantial-alteration analysis that decides whether the existing house has to come up to current energy and seismic code along with the new work. This is the workflow most owners run through, in the order most builders recommend. Click any step on the project map to read the detail. Steps stacked side-by-side run in parallel.

1. Phase 0

   Feasibility

   Five free or near-free checks that take 2–4 weeks and tell you whether the project is real before you spend a dollar on design. Setbacks and lot coverage decide whether the addition fits, and a 30-minute scope-sizing exercise tells you which budget band you're actually in.

   2-4 weeks·Free to ~$600 (test kits)·5 steps
   1. 2 in parallel
      0.1Confirm setbacks, lot coverage, and FAR for your lotPull your lot up on SDCI's GIS portal and read the setback, lot-coverage, and FAR rules — that's how you find out whether a front, side, or rear addition actually fits before you spend a dollar.Homeowner1-2 days · Free0.2Pull SDCI permit and site history for your addressRun your address through SDCI's permit research tool to find every prior permit, code violation, or open notice on the property. Free, takes about 15 minutes, surfaces things that would otherwise blow up the project mid-build.Homeowner15 minutes · Free
   2. 2 in parallel
      0.3Decide which scope band you're actually inA 30-minute exercise that picks the right project shape for your budget and goals. Four bands run from $50K kitchen-and-bath refresh to $1M down-to-studs. This workflow covers the middle two — the answer here decides whether you keep going.Homeowner30-60 minutes · Free0.4Walk the house with an experienced remodel GCGet a GC who has actually done a Seattle whole-house remodel + addition to walk through the house with you for an hour. They'll tell you in 60 minutes what would otherwise take you four months of design fees to discover.Homeowner, General contractor1-2 hours · Free (most do free walk-throughs)
   3. 0.5Pre-screen the house for lead and asbestosIf the house was built before 1978, federal lead RRP rules apply during construction; before 1980, WA asbestos rules apply during demo. A $300–$600 inspection confirms what you're dealing with so the bid can include the right abatement scope.Homeowner1-2 weeks · $300-$600
2. Phase 1

   Site and existing conditions

   Three or four documents that describe what you've actually got: a measured survey of the lot, a measured drawing of the existing house, a structural read on the foundation and the addition tie-in, and (sometimes) a soils report. The designer needs all of this before they can draw anything.

   4-8 weeks·$3,500-$15,000·4 steps
   1. 2 in parallel
      1.1Order a boundary and topographic surveyHire a licensed land surveyor to set the property corners, shoot the topography, and locate trees and existing improvements. The designer can't draw setbacks or coverage without it.Surveyor2-4 weeks · $1,500-$3,5001.2Measured drawings of the existing houseThe designer measures every wall, window, door, and floor-to-ceiling dimension of the existing house. The new design lays on top of these drawings — they have to be accurate to the eighth-of-an-inch.Designer1-2 weeks · $1,500-$4,000 (often included in design fee)
   2. 2 in parallel
      1.3Foundation assessment and addition tie-in evaluationA licensed structural engineer inspects the existing foundation and walks the addition footprint. Two questions: is the existing foundation OK as-is for the existing house, and how does the new addition foundation tie into it?Structural eng.2-4 weeks · $1,500-$3,500 (assessment only; full design comes later)1.4Order a soils or geotech report if conditions require itLots in environmentally critical areas (ECAs), on slopes, or with poor drainage may require a soils investigation. Most flat inner-city lots don't.Geotech eng.3-5 weeks · $2,500-$6,000
3. Phase 2

   Design and engineering

   This is the longest phase. Engage a designer with whole-house remodel experience, develop the program with kitchen-first thinking, work through schematic to permit-ready drawings, design the kitchen specifically, get the structural engineering for wall removals and the tie-in, and run the substantial-alteration analysis.

   4-7 months·$25,000-$50,000·6 steps
   1. 2.1Engage an architect or designer with whole-house remodel experienceAn architect or designer who has finished Seattle whole-house remodels runs the design phase, coordinates the structural engineer and kitchen designer, and shepherds the SDCI submittal through correction loops.Designer, Architect1-3 weeks to hire · Design fee 8-12% of construction cost ($25K-$60K typical)
   2. 2.2Program development with kitchen-first thinkingBefore any drawing happens, work out the program: which rooms, what sizes, what adjacencies. On a whole-house remodel, the kitchen drives most of these decisions — work it out first, then everything else follows.Homeowner, Designer2-4 weeks · Included in design fee
   3. 2 in parallel
      2.3Schematic design through design developmentDesigner takes the program and produces preliminary plans, elevations, and a kitchen study. You iterate. By the end you have a building that fits the lot, fits the budget, and fits the family.Designer, Homeowner8-14 weeks · Included in design fee2.4Kitchen design — work triangle, appliance specs, MEP coordinationThe kitchen gets a dedicated design pass: cabinet layout, work-triangle resolution, appliance specifications, and the MEP coordination that drops out of the appliance schedule. This is where most of the project's design value lives.Designer, Homeowner4-8 weeks (overlaps with schematic) · Included in design fee; specialty kitchen-and-bath designer adds $2K-$8K
   4. 2 in parallel
      2.5Structural engineering — wall removals, addition framing, tie-inThe structural engineer designs the new addition foundation and framing, the tie-in to existing, and the beams + posts for every interior wall removal. Stamped drawings and calcs become part of the permit set.Structural eng.5-8 weeks · $4,000-$12,0002.6WSEC compliance and substantial-alteration analysisAn energy consultant or your designer runs the Seattle Energy Code alteration provisions and produces the substantial-alteration analysis under SDCI Tip 314. The conclusion decides whether the existing house has to be brought up to current energy and seismic code.Energy consultant, Designer3-5 weeks · $1,500-$5,000
4. Phase 3

   Permits and approvals

   Submit the permit-ready set to SDCI as an Addition/Alteration, kick off the sub-permits, navigate any tree review that applies, and respond to corrections. Plan for 1–3 correction cycles; substantial-alteration projects often run longer.

   3-6 months·$8,000-$25,000 (SDCI fees + sub-permit fees)·4 steps
   1. 3.1Submit the Addition/Alteration permit to SDCIDesigner uploads the permit set, structural calcs, energy compliance, substantial-alteration analysis, and survey to SDCI's permitting portal. SDCI triages, charges intake fees, and assigns the application to reviewers.Designer, SDCI, Homeowner2-3 weeks to intake; 6-10 weeks to first review · Intake fee + plan review fees pro-rated to project value
   2. 3.2Pull electrical, plumbing, and mechanical sub-permitsThe GC pulls sub-permits under the master Addition/Alteration permit for electrical, plumbing, and mechanical work. Each sub-permit is reviewed and inspected separately.Electrician, Plumber, HVAC contractor, General contractorRun in parallel with main permit; each issues in 1-3 weeks · $500-$2,000 per trade
   3. 3.3Tree review (SMC 25.11) if regulated trees applySDCI's tree code regulates protected and exceptional trees on residential lots. A whole-house addition can trigger tree review if construction activity falls within a regulated tree's protection zone.SDCI2-4 weeks · $100-$1,500
   4. 3.4Respond to SDCI correction letters (1-3 cycles typical)Your designer turns SDCI's review comments into revised drawings and a response letter. Each cycle is 4-6 weeks. Most projects clear in 1-3 cycles; substantial-alteration projects can run 2-4.Designer, Architect, SDCI4-6 weeks per cycle, 1-3 cycles typical · Included in design fee; SDCI hourly rate applies if review goes long
5. Phase 4

   Bid and contract

   Send the permit-ready set to three to five GCs who match your scope band. Verify them, decide on phasing, negotiate the contract, sign it, and figure out where the family lives during the build.

   6-10 weeks·$2,000-$8,000 (insurance + attorney + temporary housing setup)·4 steps
   1. 4.1Solicit bids from 3-5 Seattle whole-house remodel GCsSend your permit-ready plans to three to five GCs who match your scope band, and ask them all to bid the same scope so you can compare apples to apples.Homeowner, General contractor3-4 weeks · Free
   2. 4.2Verify GC license, bond, insurance, and remodel historyPull L&I status (active, bonded, insured), check recent Seattle remodel permits, confirm RRP certification if your house is pre-1978, and walk one finished project. About 30 minutes plus a site visit.Homeowner1-2 days · Free
   3. 4.3Negotiate and sign the GC contractFixed-price is what most owners want. Cost-plus only works with a guaranteed maximum price (GMP) cap. On contracts over $300K, an attorney review pays for itself.Homeowner, General contractor, Attorney1-2 weeks · $1,000-$4,000 if attorney-reviewed
   4. 4.4Decide phasing strategy and where the family livesMost whole-house remodels finish faster and cost less if done all at once with the family moved out. Some owners phase — kitchen first, bedrooms later — to stay in the house longer. Both work; pick deliberately.Homeowner, General contractor, Insurance1-2 weeks · Decision is free; consequences run $20K-$80K
6. Phase 5

   Build

   Six to twelve months of construction. Abatement first, then the addition foundation and shell, then interior demo and framing (including wall removals), then MEP rough, then insulation and drywall, then the kitchen and finishes, then the inspection sequence that gets you to substantial completion.

   6-12 months·Built into the GC contract; allowance lines true up against actual·7 steps
   1. 5.1Lead and asbestos abatementBefore any meaningful demo, the asbestos abatement contractor (separately licensed) and lead-RRP-certified GC handle the regulated materials. One to three weeks; produces clearance documentation.General contractor1-3 weeks · $5,000-$25,000 (varies with how much asbestos and lead is present)
   2. 5.2Addition foundation, tie-in, and shellThe new addition gets its foundation poured, the tie-in to the existing foundation is detailed and inspected, and the addition framing goes up. The existing house is mostly untouched during this phase.General contractor, Structural eng.4-8 weeks · Built into GC contract
   3. 5.3Interior demo and structural framing (wall removals + new framing)The existing house gets gutted to the level the scope requires, interior bearing walls come out and beams go in, and the addition's interior framing ties in. The most disruptive phase.General contractor, Structural eng.6-12 weeks · Built into GC contract
   4. 5.4MEP rough-in + service upgrade (SCL)Electrical, plumbing, and mechanical roughs go in the open framing. SCL upgrades the electric service if needed. Each trade gets a separate inspection before drywall.Electrician, Plumber, HVAC contractor, Seattle City Light5-9 weeks · Built into GC contract; SCL service upgrade $0-$5,000 typical
   5. 5.5Insulation, drywall, paint, and rough finishesWalls and ceilings get insulated, drywalled, taped, primed, painted. Trim goes on. Floors go down. Stage one of the finish phase — gets the envelope and rough finishes done before the kitchen install.General contractor6-10 weeks · Built into GC contract
   6. 5.6Kitchen install + bathroom finishes + appliance setCabinets, counters, tile, fixtures, and appliances. The longest finish phase because of cabinet and counter lead times. Aim to start ordering at end of framing.General contractor6-10 weeks · Built into GC contract; allowances true up against actual
   7. 5.7Final inspections and tests (energy, blower-door, mechanical)Code-required tests and inspections before final occupancy: blower-door air leakage test, duct leakage test, final mechanical, final plumbing, final electrical, final building.General contractor, Energy consultant, SDCI1-2 weeks · Built into GC contract; testing fees $400-$1,000
7. Phase 6

   Final inspection, move back in, and home record

   Certificate of Occupancy issues, the family moves back in, the warranty walk happens, and the remodel becomes part of the permanent home record.

   3-6 weeks·Move-back logistics + minor punch-list items·3 steps
   1. 6.1Final building inspection and Certificate of OccupancySDCI's final building inspector signs off on the project. The Certificate of Occupancy (CofO) is the legal document that says you can move in.SDCI, General contractor1-2 weeks · Included in permit fees
   2. 6.2Move back in and conduct the warranty walkMove the family back, live with the new house for two to four weeks, then walk the project with the GC to identify warranty items. Most contracts cover one year of workmanship; document items as you find them.Homeowner, General contractor2-4 weeks · Move-back logistics + minor punch-list
   3. 6.3Update the home record with remodel documentationAdd the remodel's permit set, certificate of occupancy, structural and energy documentation, abatement records, and warranty paperwork to your home record. Future buyers, insurers, and your own future self will all need it.Homeowner1-2 hours · Free