The Cost Stack
| Group | What it includes | How to control it |
|---|---|---|
| Land | Purchase price or current land value | Already fixed if you own the lot |
| Demolition & abatement | Hazmat survey, asbestos removal, demolition, disposal | Survey early; salvage where possible |
| Site work & utilities | Excavation, grading, retaining walls, stormwater, side sewer, water meters, power | Choose a layout that follows the grade and keeps utility runs short |
| Design & engineering | Architect, civil, structural, geotech, survey, arborist | Commit to a building type before full design |
| Permits & fees | Plan review, building and site permits, school/park/traffic impact fees, utility connection charges | Model fees per city before buying land |
| Construction | Foundations, framing, envelope, MEP, finishes | Repeat floor plans across units; avoid complex roofs |
| Financing & contingency | Loan interest, points, insurance, contingency reserve | Shorten permitting time; keep 8–10% contingency |
Why Two Homes Cost More Than Half of Four
Many costs are fixed per project: the survey, the civil design, the side sewer, the pre-application meeting, the street frontage. Spread across two homes, they are heavy; across four or six, they shrink per unit. That is why lots that allow four homes often produce a better return than lots limited to two, even after the extra construction.
The Code Threshold
Duplexes and townhouses are usually built under the residential code. Three or more stacked homes generally trigger the commercial building code, with fire sprinklers, more fire-rated assemblies and, at four or more units, Fair Housing Act accessibility. Expect a noticeable cost-per-square-foot jump at that line — sometimes enough to make townhomes cheaper per home than a fourplex.
Fees Vary More Than People Expect
Impact fees are set by each city and school district, and utility connection charges by each water and sewer provider. Two lots a mile apart, one in Lynnwood and one in unincorporated Snohomish County, can carry very different fee totals. We pull current fee schedules for every feasibility package.
Finishes: Rental Grade vs. Owner Grade
| Item | Rental standard | Owner/market standard |
|---|---|---|
| Flooring | Luxury vinyl plank throughout | LVP or engineered wood, tile in baths |
| Counters | Quartz, standard edge | Quartz with full-height backsplash |
| Cabinets | Stock | Semi-custom |
| Fixtures | Durable mid-range | Upgraded fixtures, tiled shower |
| Exterior | Fiber cement lap | Mixed cladding, wood accents |
The gap between columns typically adds 15–25% to construction cost.
Estimate Your Own Project
Use the calculator to model your lot with editable assumptions → Build Cost & Return Calculator