Primary Suite Addition in Portland: Cost, Layouts & Timeline
What 400 to 700 square feet of new suite costs, where to put it, and how to make the bathroom work.
Quick Answer
A primary suite addition in Portland runs $400–$700 per square foot, so a typical 400–700 sq ft suite lands between $160,000 and $490,000. Main-floor additions are usually the least expensive per square foot, second-story and over-garage suites the most, because of foundation and structural work. Expect 4–8 weeks of design, 6–16 weeks of permitting and 3–6 months of construction.
Masters Construction (also listed as Masters Construction Group) is a design-build general contractor serving Portland, Lake Oswego, West Linn, and Vancouver, WA.
The primary suite addition is the most requested single project we build. The reason is consistent: people love their house and their street, and they have outgrown a 12-by-13 bedroom with a hall bath and a closet the width of a door. This guide covers what the addition costs, the three places it can go, the bathroom layouts that actually work in the square footage available, and how to make new construction look like it was always there.
What does a primary suite addition cost in Portland?
Additions price at $400–$700 per square foot in the Portland metro. A suite of 400–700 square feet therefore runs roughly $160,000 to $490,000 — a wide spread that is almost entirely explained by three variables.
Plumbing runs. A suite placed near existing wet walls is meaningfully cheaper than one at the far corner of the house. Long supply and waste runs mean opened floors, new venting, and sometimes a pump — real money before any tile is set.
Level. A ground-floor addition needs a foundation but nothing else structural in the existing house. A second-story suite requires evaluating and often reinforcing the foundation, the bearing walls and the floor system beneath it, plus temporary weather protection during the build.
The bathroom. A spa bath with a curbless shower, a freestanding tub, heated floors, double vanity and slab tile can cost as much as the bedroom, closet and hallway combined. This is the line item that most often moves a project from $250,000 to $400,000.
Detailed ranges by room are in our remodeling cost guide, and what our price includes is on the pricing page.
Main-floor, second-story or over-garage — which suite is right?
Main floor. The most popular option for clients who intend to stay in the house long term, and usually the lowest cost per square foot. It typically extends off the rear or side, often absorbing a back bedroom or a covered porch. Downsides: it consumes yard, it needs a clean foundation path, and on tight lots it runs into setbacks.
Second story. Best where the lot is small or the yard is precious, and the only option on many close-in Portland lots. It requires a structural evaluation of the foundation and bearing path below, and it is the most expensive per square foot. It also gives the best views and the cleanest separation from the rest of the house.
Over the garage. Often the efficient compromise — the foundation and walls exist, and the suite sits away from the main living rooms. The catches are insulation and sound isolation above an unconditioned garage, and a garage slab and stem wall that may not have been designed to carry living space. An engineer settles that question before design goes far.
Which spa bathroom layouts actually work?
A primary bath needs about 100–150 square feet to hold everything comfortably; below 80 it becomes a set of compromises. The arrangement that works most reliably: a wet zone along the back wall with a curbless shower and the freestanding tub sharing the glass, a double vanity on the long opposite wall, and a separate water closet behind a door near the entry.
Curbless shower. Requires the floor framing to be dropped or the tile floor built up so the drain has slope. It is a framing decision, not a tile decision, and has to be made before the floor system is built. Linear drains along the back wall keep the floor plane clean.
Freestanding tub. Beautiful, and worth being honest about: it is harder to clean around and requires either a floor-mounted filler (which needs framing coordination and a shutoff plan) or a wall filler. Place it where it gets natural light and it becomes the reason the room feels like a hotel.
Double vanity. Thirty inches of clear width per person is the practical minimum; 36 is better. Full-height mirrors and lighting at face height rather than overhead do more for the room than an expensive faucet.
Heated floors. Electric mats under tile are inexpensive to install during construction and impossible to add later. In Portland's damp winters, nearly every client who has them says it is their favorite detail.
How should you plan the walk-in closet?
Sixty to a hundred square feet handles two people well. The layout matters more than the size: a U-shape with 36–42 inches of clear aisle beats a long galley of the same area, because both people can be in it at once.
Plan double-hang for the majority of the run — it doubles capacity in the same wall length — with a single long-hang section for dresses and coats, drawers inside the closet rather than in the bedroom, and shoe shelving sized to what you own rather than a generic allocation. Lighting should be inside the closet at the hanging rods, not a single ceiling fixture that puts you in your own shadow.
If the closet can take a window or a skylight, take it. A closet with daylight is the difference between a storage room and part of the suite.
Can you expand a cramped existing primary instead of adding on?
Frequently, yes — and it is usually cheaper than new square footage. Three approaches cover most houses.
Bump-out. Extending the existing bedroom 6–10 feet on a cantilever or a small new foundation adds enough for a sitting area or a closet wall without a full addition footprint. Often the best value per dollar in the whole category.
Borrowing the adjacent bedroom. Where a family has aged out of a four-bedroom layout, absorbing the neighboring room converts an ordinary primary into a suite with a real closet and bath for the cost of interior reconfiguration and plumbing — no foundation, no roof, no permitting delay for new footprint.
Converting an adjacent bath or hall. A hall bath backing onto the primary can be captured and rebuilt as an ensuite, with the family bath relocated elsewhere. This keeps plumbing where it is, which is exactly where you want it.
We evaluate all three at the consultation before recommending an addition. If reconfiguring gets you 85% of the result for 50% of the money, we will say so.
How do you match the addition to the existing house?
The tell of a bad addition is always the roof. A new gable at the wrong pitch, or a shed roof grafted onto a hipped house, announces itself from the street permanently. We measure the existing pitch and continue it, or use a form the original architecture already contains elsewhere on the house.
Window proportions come second. Old houses have vertical windows with specific muntin patterns; a new horizontal unit in the same wall plane looks wrong even to people who cannot say why. We match the proportion and the pattern, then upgrade the glazing performance behind it.
Then siding exposure and trim. Lap siding has a specific reveal; matching it and the corner-board and window-casing profiles matters more than matching the paint, which will be repainted anyway. Where the original material is no longer produced, we mill it.
Finally, the connection point. We prefer a slight setback or a change of plane where old meets new, so the junction reads as intentional rather than as a seam.
How long does a primary suite addition take?
Design: 4–8 weeks, including the structural approach and the bathroom layout resolved in 3D. Engineering and permits: 6–16 weeks depending on jurisdiction and whether the work is over an existing structure. Construction: 3–6 months for a main-floor suite, toward the upper end and beyond for second-story work.
During permitting we order the long-lead items — windows, tile, plumbing fixtures, custom glass and cabinetry — so the site never waits on a delivery that could have been ordered three months earlier.
What permits and engineering are required?
Every addition that creates new conditioned floor area requires a building permit and a stamped structural design. That means a foundation plan, a framing plan with beam and header sizes, shear and lateral details, an energy code compliance path, and mechanical, electrical and plumbing scope on the drawings.
In Portland, BDS reviews the set and typically takes 10–16 weeks on an addition; conservation and historic overlays add design review. Lake Oswego and West Linn are often faster on paper but sensitive to setbacks, tree removal, slope and sensitive-lands overlays. In Vancouver, WA the City and Clark County are separate jurisdictions with separate processes.
A second-story or over-garage suite always triggers an engineer's evaluation of what is below it. We commission that evaluation early, because the answer changes both the design and the budget, and it is better known in week three than month three.
Frequently Asked
Frequently Asked Questions
What homeowners ask us most about this work.
$400–$700 per square foot, so a typical 400–700 sq ft suite runs $160,000–$490,000. Long plumbing runs, second-story construction and a spa-level bathroom push the number toward the top of that range.
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