Skip to main content Skip to content Portland's design-build firm for finished basements, in-law suites, ADU conversions, theaters, and wine rooms. One contract from the moisture log to the final walkthrough.
A finished basement in Portland runs $85,000 to $385,000 in 2026. Most projects land between $145,000 and $245,000 for a 1,000 to 1,400 square foot living suite with a wet bar, full bathroom, and bedroom. ADU conversions reach $260,000 to $385,000 once you add a kitchen, separate entry, and code-required egress windows. The figure changes most with three variables: ceiling height (excavation or underpinning), moisture management scope, and finish level.
Most Portland basements were built to be ignored. The high-end ones get a second life: an in-law suite that pays the mortgage, a theater the kids actually use, a wine room that finally earns its square footage. Done right, it adds the equivalent of a full upper floor without changing the roofline.
Tyrell has run more than 80 Portland basement and ADU projects since 2017, including five in pre-1940 daylight basements where ceiling height, knob-and-tube wiring, and waterproofing all had to be solved before framing could start. He owns the schedule, the budget, and the moisture log on every basement we build.
A finished basement is the highest-leverage square footage in a Portland home. You already own the foundation, the slab, the perimeter walls. The job is to add light, height, and air, then build out from there.
Most clients come in describing one of these five. They sit at different price points, different permit paths, and very different finish levels. Knowing which one you're after sharpens the design phase from the first meeting.
The most common scope: a great room with a wet bar, powder bath, and built-in storage. Adds about 800 to 1,200 square feet of true living space.
Bedroom, full bath, sitting area, and kitchenette. Egress window is non-negotiable. Designed for a parent, an adult child, or long-term guests.
Climate-controlled cellar (55 to 58 degrees, 60 to 70 percent humidity), a tasting bar, racking for 800 to 2,400 bottles, and a tucked-away serving prep area.
Acoustically isolated theater with riser seating, plus a gym, sauna, or cold plunge in the adjacent zone. Sound and HVAC are the hard problems here.
Full kitchen, full bath, separate entry, dedicated electrical, and a permit certificate of occupancy. Rentable from day one. Pays the mortgage in 8 to 11 years.
None of these are required. All of them show up on the basements we're proudest of. We surface them in the design phase so you can choose what fits the budget and what waits for phase two.
Warm slab from the moment you take the stairs. Closed-loop PEX in 1.5-inch poured topping, zoned per room, sized for a 65-degree slab in February.
Full window-well excavation with a powder-coated steel surround and a horizontal-slider egress unit. Code-compliant and visually quiet from the yard.
Walnut or oak millwork, undercounter beverage column, U-Line clear-ice maker on a sound-isolated mount. Reads as a bar, not a kitchenette.
Double-stud wall, Green Glue between two layers of Type X drywall, resilient channel ceiling assembly. Tested at STC 58 minimum on the shared wall.
Whole-basement low-voltage dimming on a single Lutron RadioRA 3 keypad per room. Scenes for movie night, dinner party, kids reading, after midnight.
HVAC trunks, plumbing risers, and electrical panel relocated into a chase or moved upstairs. Ceiling reads flat, not industrial. Adds 4 to 6 inches of usable height.
Wealthy Portland clients ask the same questions at the kitchen table: What's behind the drywall? What happens in February when the ground saturates? Here's what the wall sections look like before the finishes go on.
Six inches of fall in the first ten feet. Downspouts to daylight or a dry well, never to grade. We document every line before we frame the first wall.
French drain in a 6-inch trench against the footing, sleeved gravel, fed to a sealed sump basin with a primary pump and a battery-backup secondary.
10-mil reinforced poly continuous from slab to band joist, taped at every seam. Closed-cell spray foam outboard of the framing for true thermal break.
DRIcore or Delta-FL panels lift the finished floor 1.5 inches off the slab, breaking thermal bridging and giving any incidental moisture somewhere to go.
Code minimum 7 feet (6 feet 8 inches under beams). On pre-1950 homes we often gain 4 to 8 inches by relocating mechanicals and deepening the slab.
Required in every sleeping area: 5.7 square feet of openable area, 24-inch min height, sill no more than 44 inches off the finished floor.
HVAC trunks routed inside soffits, plumbing risers consolidated into a chase wall, panel relocated when needed. The ceiling plane stays flat.
Dedicated dehumidifier (Aprilaire E100 or larger), HRV for fresh air, MERV 13 filtration. Indoor air below 50 percent RH year-round.
Below-grade flooring has to handle vapor, thermal bridging, and the occasional minor incident. These are the three systems we trust on Portland basements.
Most Popular 9-inch wide-plank European white oak, dimensionally stable over a sub-floor system. Reads as a primary floor, not a basement floor. Best for family lounges and ADUs.
For Wine & Theater Honed, densified, and sealed slab over hydronic radiant. Visually grounded, thermally connected, ideal for wine rooms and contemporary theaters.
For Wet Areas 24x48 rectified porcelain over Schluter Ditra-HEAT. Indestructible against incidental moisture, paired with wool rugs to soften the read. Used most often in theater foyers and ADU baths.
Basements have more upstream variables than any other remodel: moisture, ceiling height, code, mechanical relocation, egress. Our 7-step process front-loads every one of them so the construction phase is execution, not problem-solving.
Free in-home consult, scope conversation, and a 30-day RH and temperature log placed on the slab. We don't quote a basement until we've seen at least three weeks of data.
Anna and the design team produce floor plans, elevations, and 3D walkthroughs. Structural engineer reviews any underpinning, beam relocation, or post-tension loading.
Material library presented, every selection priced, every line item visible. You see the budget for cabinetry, the budget for tile, the budget for the dehumidifier. Nothing rolls into a single allowance.
We file with Portland BDS, manage every reviewer comment, and respond within 48 hours. Q1 2026 average review time for Type 1 residential: 7.5 weeks.
Existing finishes out, perimeter drain in, sump pump installed, vapor barrier and closed-cell foam applied. The hardest week of the project. Done before any framing begins.
Framing, mechanical rough-in, inspections, drywall, paint, flooring, millwork, fixtures, lighting, trim. One PM (Tyrell), one schedule, weekly Friday check-ins.
City final, certificate of occupancy (for ADUs), homeowner walkthrough with punch list, then a 30-day, 6-month, and 1-year follow-up. One-year craftsmanship warranty starts on close.
Featured Project · Hemlock A 1947 Tudor with a 6-foot-2 ceiling, knob-and-tube wiring, and a perimeter that took on water every February. We underpinned the footings to gain 14 inches of height, ran a new perimeter drain, replaced the entire mechanical core, and finished 1,180 square feet as a daylight family lounge with a walnut wet bar and a guest bath.
Basement-inclusive whole-home projects from the last 18 months. Click through to the full case study in our project gallery.
A finished basement in Portland runs $85,000 to $385,000 in 2026. Most projects land between $145,000 and $245,000 for a full living suite (1,000 to 1,400 square feet) with a wet bar, full bath, and bedroom. ADU conversions reach $260,000 to $385,000 once you add a kitchen, separate entry, and code-required egress.
Most Portland basements built after 1970 can be converted to a legal ADU. The 2026 City of Portland code requires 7-foot ceiling minimum (6 feet 8 inches under beams), an egress window in any sleeping area, dedicated electrical service, and either an interior or exterior entry. Pre-1970 daylight basements often qualify after underpinning or window-well excavation. We'll know within one site visit whether yours is a candidate.
A finished basement ADU in Portland rents for $1,650 to $2,950 per month in 2026, depending on neighborhood and square footage. Lake Oswego, Pearl District, and Sellwood basement ADUs trend toward the upper end. A 900-square-foot one-bedroom ADU near a MAX line typically pays back the conversion in 8 to 11 years.
Every project starts with a 30-day moisture log and exterior grading review. We install a perimeter drain (interior or exterior depending on access), a continuous vapor barrier behind framing, closed-cell spray foam insulation, and a sealed sub-floor system that lifts finished flooring 1.5 inches above slab. The final assembly carries a 10-year transferable moisture warranty from our waterproofing partner. Sump basin includes a battery-backup secondary pump.
Plan for 14 to 22 weeks from design start to final walkthrough. Design phase: 4 to 6 weeks. Permit review: 6 to 10 weeks (Portland BDS averaged 7.5 weeks for Type 1 residential in Q1 2026). Construction: 12 to 18 weeks. ADU conversions add 2 to 4 weeks for kitchen rough-in and a separate utility meter.
Remodeling Magazine's 2026 Cost vs. Value Report puts midrange basement finishes at 70 to 78 percent recovery in the Pacific Northwest. ADU conversions perform stronger: a Multnomah County tax assessor study (2025) found legal basement ADUs added 18 to 24 percent to appraised value. A theater or wine room is more lifestyle than ROI.
Yes. When the basement floor sits below the main sewer line, we install a Liberty Pumps Pro380 or Saniflo Sanibest system with a sealed basin, alarm, and battery backup. We oversize the lift capacity for future fixture additions and run the discharge through a quiet-spec PVC riser inside a soffit.
Most of our basement projects are within a 40-minute drive of our Pearl District office. Below are the metros and neighborhoods we book most often in 2026.
Free in-home consultation, itemized estimate within one business day, and a 30-day moisture log before we propose a single detail. Now booking 2026 basement and ADU projects.
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